// SPDX-FileCopyrightText: 2022-2023 The go-mail Authors
//
// SPDX-License-Identifier: MIT

package mail

import (
	"embed"
	"fmt"
	"reflect"
	"strings"
	"testing"
)

var (
	charsetTests = []struct {
		name  string
		value Charset
		want  Charset
	}{
		{"UTF-7", CharsetUTF7, "UTF-7"},
		{"UTF-8", CharsetUTF8, "UTF-8"},
		{"US-ASCII", CharsetASCII, "US-ASCII"},
		{"ISO-8859-1", CharsetISO88591, "ISO-8859-1"},
		{"ISO-8859-2", CharsetISO88592, "ISO-8859-2"},
		{"ISO-8859-3", CharsetISO88593, "ISO-8859-3"},
		{"ISO-8859-4", CharsetISO88594, "ISO-8859-4"},
		{"ISO-8859-5", CharsetISO88595, "ISO-8859-5"},
		{"ISO-8859-6", CharsetISO88596, "ISO-8859-6"},
		{"ISO-8859-7", CharsetISO88597, "ISO-8859-7"},
		{"ISO-8859-9", CharsetISO88599, "ISO-8859-9"},
		{"ISO-8859-13", CharsetISO885913, "ISO-8859-13"},
		{"ISO-8859-14", CharsetISO885914, "ISO-8859-14"},
		{"ISO-8859-15", CharsetISO885915, "ISO-8859-15"},
		{"ISO-8859-16", CharsetISO885916, "ISO-8859-16"},
		{"ISO-2022-JP", CharsetISO2022JP, "ISO-2022-JP"},
		{"ISO-2022-KR", CharsetISO2022KR, "ISO-2022-KR"},
		{"windows-1250", CharsetWindows1250, "windows-1250"},
		{"windows-1251", CharsetWindows1251, "windows-1251"},
		{"windows-1252", CharsetWindows1252, "windows-1252"},
		{"windows-1255", CharsetWindows1255, "windows-1255"},
		{"windows-1256", CharsetWindows1256, "windows-1256"},
		{"KOI8-R", CharsetKOI8R, "KOI8-R"},
		{"KOI8-U", CharsetKOI8U, "KOI8-U"},
		{"Big5", CharsetBig5, "Big5"},
		{"GB18030", CharsetGB18030, "GB18030"},
		{"GB2312", CharsetGB2312, "GB2312"},
		{"TIS-620", CharsetTIS620, "TIS-620"},
		{"EUC-KR", CharsetEUCKR, "EUC-KR"},
		{"Shift_JIS", CharsetShiftJIS, "Shift_JIS"},
		{"GBK", CharsetGBK, "GBK"},
		{"Unknown", CharsetUnknown, "Unknown"},
	}
	encodingTests = []struct {
		name  string
		value Encoding
		want  Encoding
	}{
		{"Quoted-Printable", EncodingQP, "quoted-printable"},
		{"Base64", EncodingB64, "base64"},
		{"Unencoded (8-Bit)", NoEncoding, "8bit"},
		{"US-ASCII (7-Bit)", EncodingUSASCII, "7bit"},
	}
	pgpTests = []struct {
		name  string
		value PGPType
	}{
		{"No PGP encoding", NoPGP},
		{"PGP encrypted", PGPEncrypt},
		{"PGP signed", PGPSignature},
	}
	boundaryTests = []struct {
		name  string
		value string
	}{
		{"test123", "test123"},
		{"empty string", ""},
	}
	mimeTests = []struct {
		name  string
		value MIMEVersion
		want  MIMEVersion
	}{
		{"1.0", MIME10, "1.0"},
		{"1.1 (not a valid version at this time)", MIMEVersion("1.1"), "1.1"},
	}
)

//go:embed README.md
var efs embed.FS

func TestNewMsg(t *testing.T) {
	t.Run("create new message", func(t *testing.T) {
		message := NewMsg()
		if message == nil {
			t.Fatal("message is nil")
		}
		if message.addrHeader == nil {
			t.Errorf("address header map is nil")
		}
		if message.genHeader == nil {
			t.Errorf("generic header map is nil")
		}
		if message.preformHeader == nil {
			t.Errorf("preformatted header map is nil")
		}
		if message.charset != CharsetUTF8 {
			t.Errorf("default charset for new Msg mismatch. Expected: %s, got: %s", CharsetUTF8,
				message.charset)
		}
		if message.encoding != EncodingQP {
			t.Errorf("default encoding for new Msg mismatch. Expected: %s, got: %s", EncodingQP,
				message.encoding)
		}
		if message.mimever != MIME10 {
			t.Errorf("default MIME version for new Msg mismatch. Expected: %s, got: %s", MIME10,
				message.mimever)
		}
		if reflect.TypeOf(message.encoder).String() != "mime.WordEncoder" {
			t.Errorf("default encoder for new Msg mismatch. Expected: %s, got: %s", "mime.WordEncoder",
				reflect.TypeOf(message.encoder).String())
		}
		if !strings.EqualFold(message.encoder.Encode(message.charset.String(), "ab12§$/"),
			`=?UTF-8?q?ab12=C2=A7$/?=`) {
			t.Errorf("default encoder for new Msg mismatch. QP encoded expected string: %s, got: %s",
				`=?UTF-8?q?ab12=C2=A7$/?=`, message.encoder.Encode(message.charset.String(), "ab12§$/"))
		}
	})
	t.Run("new message with nil option", func(t *testing.T) {
		message := NewMsg(nil)
		if message == nil {
			t.Fatal("message is nil")
		}
	})
	t.Run("new message with custom charsets", func(t *testing.T) {
		for _, tt := range charsetTests {
			t.Run(tt.name, func(t *testing.T) {
				message := NewMsg(WithCharset(tt.value), nil)
				if message == nil {
					t.Fatal("message is nil")
				}
				if message.charset != tt.want {
					t.Fatalf("NewMsg(WithCharset(%s)) failed. Expected charset: %s, got: %s", tt.value, tt.want,
						message.charset)
				}
			})
		}
	})
	t.Run("new message with custom encoding", func(t *testing.T) {
		for _, tt := range encodingTests {
			t.Run(tt.name, func(t *testing.T) {
				message := NewMsg(WithEncoding(tt.value), nil)
				if message == nil {
					t.Fatal("message is nil")
				}
				if message.encoding != tt.want {
					t.Errorf("NewMsg(WithEncoding(%s)) failed. Expected encoding: %s, got: %s", tt.value,
						tt.want, message.encoding)
				}
			})
		}
	})
	t.Run("new message with custom MIME version", func(t *testing.T) {
		for _, tt := range mimeTests {
			t.Run(tt.name, func(t *testing.T) {
				message := NewMsg(WithMIMEVersion(tt.value))
				if message == nil {
					t.Fatal("message is nil")
				}
				if message.mimever != tt.want {
					t.Errorf("NewMsg(WithMIMEVersion(%s)) failed. Expected MIME version: %s, got: %s",
						tt.value, tt.want, message.mimever)
				}
			})
		}
	})
	t.Run("new message with custom boundary", func(t *testing.T) {
		for _, tt := range boundaryTests {
			t.Run(tt.name, func(t *testing.T) {
				message := NewMsg(WithBoundary(tt.value))
				if message == nil {
					t.Fatal("message is nil")
				}
				if message.boundary != tt.value {
					t.Errorf("NewMsg(WithBoundary(%s)) failed. Expected boundary: %s, got: %s", tt.value,
						tt.value, message.boundary)
				}
			})
		}
	})
	t.Run("new message with custom PGP type", func(t *testing.T) {
		for _, tt := range pgpTests {
			t.Run(tt.name, func(t *testing.T) {
				message := NewMsg(WithPGPType(tt.value))
				if message == nil {
					t.Fatal("message is nil")
				}
				if message.pgptype != tt.value {
					t.Errorf("NewMsg(WithPGPType(%d)) failed. Expected PGP type: %d, got: %d", tt.value,
						tt.value, message.pgptype)
				}
			})
		}
	})
	t.Run("new message with middleware: uppercase", func(t *testing.T) {
		message := NewMsg()
		if message == nil {
			t.Fatal("message is nil")
		}
		if len(message.middlewares) != 0 {
			t.Errorf("NewMsg() failed. Expected empty middlewares, got: %d", len(message.middlewares))
		}
		message = NewMsg(WithMiddleware(uppercaseMiddleware{}))
		if len(message.middlewares) != 1 {
			t.Errorf("NewMsg(WithMiddleware(uppercaseMiddleware{})) failed. Expected 1 middleware, got: %d",
				len(message.middlewares))
		}
		message = NewMsg(WithMiddleware(uppercaseMiddleware{}), WithMiddleware(encodeMiddleware{}))
		if len(message.middlewares) != 2 {
			t.Errorf("NewMsg(WithMiddleware(uppercaseMiddleware{}),WithMiddleware(encodeMiddleware{})) "+
				"failed. Expected 2 middleware, got: %d", len(message.middlewares))
		}
	})
	t.Run("new message without default user-agent", func(t *testing.T) {
		message := NewMsg(WithNoDefaultUserAgent())
		if message == nil {
			t.Fatal("message is nil")
		}
		if !message.noDefaultUserAgent {
			t.Errorf("NewMsg(WithNoDefaultUserAgent()) failed. Expected noDefaultUserAgent to be true, got: %t",
				message.noDefaultUserAgent)
		}

	})
}

func TestMsg_SetCharset(t *testing.T) {
	t.Run("SetCharset on new message", func(t *testing.T) {
		for _, tt := range charsetTests {
			t.Run(tt.name, func(t *testing.T) {
				message := NewMsg()
				if message == nil {
					t.Fatal("message is nil")
				}
				message.SetCharset(tt.value)
				if message.charset != tt.want {
					t.Errorf("failed to set charset. Expected: %s, got: %s", tt.want, message.charset)
				}
			})
		}
	})
	t.Run("SetCharset to override WithCharset", func(t *testing.T) {
		message := NewMsg(WithCharset(CharsetUTF7))
		if message == nil {
			t.Fatal("message is nil")
		}
		if message.charset != CharsetUTF7 {
			t.Errorf("failed to set charset on message creation. Expected: %s, got: %s", CharsetUTF7,
				message.charset)
		}
		message.SetCharset(CharsetUTF8)
		if message.charset != CharsetUTF8 {
			t.Errorf("failed to set charset. Expected: %s, got: %s", CharsetUTF8, message.charset)
		}
	})
}

func TestMsg_SetEncoding(t *testing.T) {
	t.Run("SetEncoding on new message", func(t *testing.T) {
		for _, tt := range encodingTests {
			t.Run(tt.name, func(t *testing.T) {
				message := NewMsg()
				if message == nil {
					t.Fatal("message is nil")
				}
				message.SetEncoding(tt.value)
				if message.encoding != tt.want {
					t.Errorf("failed to set encoding. Expected: %s, got: %s", tt.want, message.encoding)
				}
			})
		}
	})
	t.Run("SetEncoding to override WithEncoding", func(t *testing.T) {
		message := NewMsg(WithEncoding(EncodingUSASCII))
		if message == nil {
			t.Fatal("message is nil")
		}
		if message.encoding != EncodingUSASCII {
			t.Errorf("failed to set encoding on message creation. Expected: %s, got: %s", EncodingUSASCII,
				message.encoding)
		}
		message.SetEncoding(EncodingB64)
		if message.encoding != EncodingB64 {
			t.Errorf("failed to set encoding. Expected: %s, got: %s", EncodingB64, message.encoding)
		}
	})
}

func TestMsg_SetBoundary(t *testing.T) {
	t.Run("SetBoundary on new message", func(t *testing.T) {
		for _, tt := range boundaryTests {
			t.Run(tt.name, func(t *testing.T) {
				message := NewMsg()
				if message == nil {
					t.Fatal("message is nil")
				}
				message.SetBoundary(tt.value)
				if message.boundary != tt.value {
					t.Errorf("failed to set boundary. Expected: %s, got: %s", tt.value, message.boundary)
				}
			})
		}
	})
	t.Run("SetBoundary to override WithBoundary", func(t *testing.T) {
		message := NewMsg(WithBoundary("123Test"))
		if message == nil {
			t.Fatal("message is nil")
		}
		if message.boundary != "123Test" {
			t.Errorf("failed to set boundary on message creation. Expected: %s, got: %s", "123Test",
				message.boundary)
		}
		message.SetBoundary("test123")
		if message.boundary != "test123" {
			t.Errorf("failed to set boundary. Expected: %s, got: %s", "test123", message.boundary)
		}
	})
}

func TestMsg_SetMIMEVersion(t *testing.T) {
	t.Run("SetMIMEVersion on new message", func(t *testing.T) {
		for _, tt := range mimeTests {
			t.Run(tt.name, func(t *testing.T) {
				message := NewMsg()
				if message == nil {
					t.Fatal("message is nil")
				}
				message.SetMIMEVersion(tt.value)
				if message.mimever != tt.value {
					t.Errorf("failed to set mime version. Expected: %s, got: %s", tt.value, message.mimever)
				}
			})
		}
	})
	t.Run("SetMIMEVersion to override WithMIMEVersion", func(t *testing.T) {
		message := NewMsg(WithMIMEVersion("1.1"))
		if message == nil {
			t.Fatal("message is nil")
		}
		if message.mimever != "1.1" {
			t.Errorf("failed to set mime version on message creation. Expected: %s, got: %s", "1.1",
				message.mimever)
		}
		message.SetMIMEVersion(MIME10)
		if message.mimever != MIME10 {
			t.Errorf("failed to set mime version. Expected: %s, got: %s", MIME10, message.mimever)
		}
	})
}

func TestMsg_SetPGPType(t *testing.T) {
	t.Run("SetPGPType on new message", func(t *testing.T) {
		for _, tt := range pgpTests {
			t.Run(tt.name, func(t *testing.T) {
				message := NewMsg()
				if message == nil {
					t.Fatal("message is nil")
				}
				message.SetPGPType(tt.value)
				if message.pgptype != tt.value {
					t.Errorf("failed to set pgp type. Expected: %d, got: %d", tt.value, message.pgptype)
				}
			})
		}
	})
	t.Run("SetPGPType to override WithPGPType", func(t *testing.T) {
		message := NewMsg(WithPGPType(PGPSignature))
		if message == nil {
			t.Fatal("message is nil")
		}
		if message.pgptype != PGPSignature {
			t.Errorf("failed to set pgp type on message creation. Expected: %d, got: %d", PGPSignature,
				message.pgptype)
		}
		message.SetPGPType(PGPEncrypt)
		if message.pgptype != PGPEncrypt {
			t.Errorf("failed to set pgp type. Expected: %d, got: %d", PGPEncrypt, message.pgptype)
		}
	})
}

func TestMsg_Encoding(t *testing.T) {
	t.Run("Encoding returns expected string", func(t *testing.T) {
		message := NewMsg()
		if message == nil {
			t.Fatal("message is nil")
		}
		for _, tt := range encodingTests {
			t.Run(tt.name, func(t *testing.T) {
				message.SetEncoding(tt.value)
				if message.Encoding() != tt.want.String() {
					t.Errorf("failed to get encoding. Expected: %s, got: %s", tt.want.String(), message.Encoding())
				}
			})
		}
	})
}

/*
// TestNewMsgWithMiddleware tests WithMiddleware

	func TestNewMsgWithMiddleware(t *testing.T) {
		m := NewMsg()
		if len(m.middlewares) != 0 {
			t.Errorf("empty middlewares failed. m.middlewares expected to be: empty, got: %d middleware", len(m.middlewares))
		}
		m = NewMsg(WithMiddleware(uppercaseMiddleware{}))
		if len(m.middlewares) != 1 {
			t.Errorf("empty middlewares failed. m.middlewares expected to be: 1, got: %d middleware", len(m.middlewares))
		}
		m = NewMsg(WithMiddleware(uppercaseMiddleware{}), WithMiddleware(encodeMiddleware{}))
		if len(m.middlewares) != 2 {
			t.Errorf("empty middlewares failed. m.middlewares expected to be: 2, got: %d middleware", len(m.middlewares))
		}
	}

// TestApplyMiddlewares tests the applyMiddlewares for the Msg object

	func TestApplyMiddlewares(t *testing.T) {
		tests := []struct {
			name string
			sub  string
			want string
		}{
			{"normal subject", "This is a test subject", "THIS IS @ TEST SUBJECT"},
			{"subject with one middleware effect", "This is test subject", "THIS IS TEST SUBJECT"},
			{"subject with one middleware effect", "This is A test subject", "THIS IS A TEST SUBJECT"},
		}
		m := NewMsg(WithMiddleware(encodeMiddleware{}), WithMiddleware(uppercaseMiddleware{}))
		for _, tt := range tests {
			t.Run(tt.name, func(t *testing.T) {
				m.Subject(tt.sub)
				if m.genHeader[HeaderSubject] == nil {
					t.Errorf("Subject() method failed in applyMiddlewares() test. Generic header for subject is empty")
					return
				}
				m = m.applyMiddlewares(m)
				s, ok := m.genHeader[HeaderSubject]
				if !ok {
					t.Errorf("failed to get subject header")
				}
				if s[0] != tt.want {
					t.Errorf("applyMiddlewares() method failed. Expected: %s, got: %s", tt.want, s[0])
				}
			})
		}
	}

// TestMsg_SetGenHeader tests Msg.SetGenHeader

	func TestMsg_SetGenHeader(t *testing.T) {
		tests := []struct {
			name   string
			header Header
			values []string
		}{
			{"set subject", HeaderSubject, []string{"This is Subject"}},
			{"set content-language", HeaderContentLang, []string{"en", "de", "fr", "es"}},
		}

		for _, tt := range tests {
			t.Run(tt.name, func(t *testing.T) {
				m := NewMsg()
				m.SetGenHeader(tt.header, tt.values...)
				if m.genHeader[tt.header] == nil {
					t.Errorf("SetGenHeader() failed. Tried to set header %s, but it is empty", tt.header)
					return
				}
				for _, v := range tt.values {
					found := false
					for _, hv := range m.genHeader[tt.header] {
						if hv == v {
							found = true
						}
					}
					if !found {
						t.Errorf("SetGenHeader() failed. Value %s not found in header field", v)
					}
				}
			})
		}
	}

// TestMsg_SetGenHeaderPreformatted tests Msg.SetGenHeaderPreformatted

	func TestMsg_SetGenHeaderPreformatted(t *testing.T) {
		tests := []struct {
			name   string
			header Header
			value  string
		}{
			{"set subject", HeaderSubject, "This is Subject"},
			{"set content-language", HeaderContentLang, fmt.Sprintf("%s, %s, %s, %s",
				"en", "de", "fr", "es")},
			{"set subject with newline", HeaderSubject, "This is Subject\r\n with 2nd line"},
		}

		for _, tt := range tests {
			t.Run(tt.name, func(t *testing.T) {
				m := &Msg{}
				m.SetGenHeaderPreformatted(tt.header, tt.value)
				m = NewMsg()
				m.SetGenHeaderPreformatted(tt.header, tt.value)
				if m.preformHeader[tt.header] == "" {
					t.Errorf("SetGenHeaderPreformatted() failed. Tried to set header %s, but it is empty", tt.header)
				}
				if m.preformHeader[tt.header] != tt.value {
					t.Errorf("SetGenHeaderPreformatted() failed. Expected: %q, got: %q", tt.value,
						m.preformHeader[tt.header])
				}
				buf := bytes.Buffer{}
				_, err := m.WriteTo(&buf)
				if err != nil {
					t.Errorf("failed to write message to memory: %s", err)
					return
				}
				if !strings.Contains(buf.String(), fmt.Sprintf("%s: %s%s", tt.header, tt.value, SingleNewLine)) {
					t.Errorf("SetGenHeaderPreformatted() failed. Unable to find correctly formated header in " +
						"mail message output")
				}
			})
		}
	}

// TestMsg_AddTo tests the Msg.AddTo method

	func TestMsg_AddTo(t *testing.T) {
		a := []string{"address1@example.com", "address2@example.com"}
		na := "address3@example.com"
		m := NewMsg()
		if err := m.To(a...); err != nil {
			t.Errorf("failed to set TO addresses: %s", err)
			return
		}
		if err := m.AddTo(na); err != nil {
			t.Errorf("AddTo failed: %s", err)
			return
		}

		atf := false
		for _, v := range m.addrHeader[HeaderTo] {
			if v.Address == na {
				atf = true
			}
		}
		if !atf {
			t.Errorf("AddTo() failed. Address %q not found in TO address slice.", na)
		}
	}

// TestMsg_From tests the Msg.From and Msg.GetSender methods

	func TestMsg_From(t *testing.T) {
		a := "toni@example.com"
		n := "Toni Tester"
		na := fmt.Sprintf(`"%s" <%s>`, n, a)
		m := NewMsg()

		_, err := m.GetSender(false)
		if err == nil {
			t.Errorf("GetSender(false) without a set From address succeeded but was expected to fail")
			return
		}

		if err := m.From(na); err != nil {
			t.Errorf("failed to set FROM addresses: %s", err)
			return
		}
		gs, err := m.GetSender(false)
		if err != nil {
			t.Errorf("GetSender(false) failed: %s", err)
			return
		}
		if gs != a {
			t.Errorf("From() failed. Expected: %s, got: %s", a, gs)
			return
		}

		gs, err = m.GetSender(true)
		if err != nil {
			t.Errorf("GetSender(true) failed: %s", err)
			return
		}
		if gs != na {
			t.Errorf("From() failed. Expected: %s, got: %s", na, gs)
			return
		}
	}

// TestMsg_EnvelopeFrom tests the Msg.EnvelopeFrom and Msg.GetSender methods

	func TestMsg_EnvelopeFrom(t *testing.T) {
		e := "envelope@example.com"
		a := "toni@example.com"
		n := "Toni Tester"
		na := fmt.Sprintf(`"%s" <%s>`, n, a)
		ne := fmt.Sprintf(`<%s>`, e)
		m := NewMsg()

		_, err := m.GetSender(false)
		if err == nil {
			t.Errorf("GetSender(false) without a set envelope From address succeeded but was expected to fail")
			return
		}

		if err := m.EnvelopeFrom(e); err != nil {
			t.Errorf("failed to set envelope FROM addresses: %s", err)
			return
		}
		gs, err := m.GetSender(false)
		if err != nil {
			t.Errorf("GetSender(false) failed: %s", err)
			return
		}
		if gs != e {
			t.Errorf("From() failed. Expected: %s, got: %s", e, gs)
			return
		}

		if err := m.From(na); err != nil {
			t.Errorf("failed to set FROM addresses: %s", err)
			return
		}
		gs, err = m.GetSender(false)
		if err != nil {
			t.Errorf("GetSender(false) failed: %s", err)
			return
		}
		if gs != e {
			t.Errorf("From() failed. Expected: %s, got: %s", e, gs)
			return
		}

		gs, err = m.GetSender(true)
		if err != nil {
			t.Errorf("GetSender(true) failed: %s", err)
			return
		}
		if gs != ne {
			t.Errorf("From() failed. Expected: %s, got: %s", ne, gs)
			return
		}
		m.Reset()

		if err := m.From(na); err != nil {
			t.Errorf("failed to set FROM addresses: %s", err)
			return
		}
		gs, err = m.GetSender(false)
		if err != nil {
			t.Errorf("GetSender(true) failed: %s", err)
			return
		}
		if gs != a {
			t.Errorf("From() failed. Expected: %s, got: %s", a, gs)
			return
		}
		gs, err = m.GetSender(true)
		if err != nil {
			t.Errorf("GetSender(true) failed: %s", err)
			return
		}
		if gs != na {
			t.Errorf("From() failed. Expected: %s, got: %s", na, gs)
			return
		}
	}

// TestMsg_AddToFormat tests the Msg.AddToFormat method

	func TestMsg_AddToFormat(t *testing.T) {
		a := []string{"address1@example.com", "address2@example.com"}
		nn := "Toni Tester"
		na := "address3@example.com"
		w := `"Toni Tester" <address3@example.com>`
		m := NewMsg()
		if err := m.To(a...); err != nil {
			t.Errorf("failed to set TO addresses: %s", err)
			return
		}
		if err := m.AddToFormat(nn, na); err != nil {
			t.Errorf("AddToFormat failed: %s", err)
			return
		}

		atf := false
		for _, v := range m.addrHeader[HeaderTo] {
			if v.String() == w {
				atf = true
			}
		}
		if !atf {
			t.Errorf("AddToFormat() failed. Address %q not found in TO address slice.", w)
		}
	}

// TestMsg_ToIgnoreInvalid tests the Msg.ToIgnoreInvalid method

	func TestMsg_ToIgnoreInvalid(t *testing.T) {
		a := []string{"address1@example.com", "address2@example.com"}
		fa := []string{"address1@example.com", "address2@example.com", "failedaddress.com"}
		m := NewMsg()

		m.ToIgnoreInvalid(a...)
		l := len(m.addrHeader[HeaderTo])
		if l != len(a) {
			t.Errorf("ToIgnoreInvalid() failed. Expected %d addresses, got: %d", len(a), l)
		}
		m.ToIgnoreInvalid(fa...)
		l = len(m.addrHeader[HeaderTo])
		if l != len(fa)-1 {
			t.Errorf("ToIgnoreInvalid() failed. Expected %d addresses, got: %d", len(fa)-1, l)
		}
	}

// TestMsg_AddCc tests the Msg.AddCc method

	func TestMsg_AddCc(t *testing.T) {
		a := []string{"address1@example.com", "address2@example.com"}
		na := "address3@example.com"
		m := NewMsg()
		if err := m.Cc(a...); err != nil {
			t.Errorf("failed to set CC addresses: %s", err)
			return
		}
		if err := m.AddCc(na); err != nil {
			t.Errorf("AddCc failed: %s", err)
			return
		}

		atf := false
		for _, v := range m.addrHeader[HeaderCc] {
			if v.Address == na {
				atf = true
			}
		}
		if !atf {
			t.Errorf("AddCc() failed. Address %q not found in CC address slice.", na)
		}
	}

// TestMsg_AddCcFormat tests the Msg.AddCcFormat method

	func TestMsg_AddCcFormat(t *testing.T) {
		a := []string{"address1@example.com", "address2@example.com"}
		nn := "Toni Tester"
		na := "address3@example.com"
		w := `"Toni Tester" <address3@example.com>`
		m := NewMsg()
		if err := m.Cc(a...); err != nil {
			t.Errorf("failed to set CC addresses: %s", err)
			return
		}
		if err := m.AddCcFormat(nn, na); err != nil {
			t.Errorf("AddCcFormat failed: %s", err)
			return
		}

		atf := false
		for _, v := range m.addrHeader[HeaderCc] {
			if v.String() == w {
				atf = true
			}
		}
		if !atf {
			t.Errorf("AddCcFormat() failed. Address %q not found in CC address slice.", w)
		}
	}

// TestMsg_CcIgnoreInvalid tests the Msg.CcIgnoreInvalid method

	func TestMsg_CcIgnoreInvalid(t *testing.T) {
		a := []string{"address1@example.com", "address2@example.com"}
		fa := []string{"address1@example.com", "address2@example.com", "failedaddress.com"}
		m := NewMsg()

		m.CcIgnoreInvalid(a...)
		l := len(m.addrHeader[HeaderCc])
		if l != len(a) {
			t.Errorf("CcIgnoreInvalid() failed. Expected %d addresses, got: %d", len(a), l)
		}
		m.CcIgnoreInvalid(fa...)
		l = len(m.addrHeader[HeaderCc])
		if l != len(fa)-1 {
			t.Errorf("CcIgnoreInvalid() failed. Expected %d addresses, got: %d", len(fa)-1, l)
		}
	}

// TestMsg_AddBcc tests the Msg.AddBcc method

	func TestMsg_AddBcc(t *testing.T) {
		a := []string{"address1@example.com", "address2@example.com"}
		na := "address3@example.com"
		m := NewMsg()
		if err := m.Bcc(a...); err != nil {
			t.Errorf("failed to set BCC addresses: %s", err)
			return
		}
		if err := m.AddBcc(na); err != nil {
			t.Errorf("AddBcc failed: %s", err)
			return
		}

		atf := false
		for _, v := range m.addrHeader[HeaderBcc] {
			if v.Address == na {
				atf = true
			}
		}
		if !atf {
			t.Errorf("AddBcc() failed. Address %q not found in BCC address slice.", na)
		}
	}

// TestMsg_AddBccFormat tests the Msg.AddBccFormat method

	func TestMsg_AddBccFormat(t *testing.T) {
		a := []string{"address1@example.com", "address2@example.com"}
		nn := "Toni Tester"
		na := "address3@example.com"
		w := `"Toni Tester" <address3@example.com>`
		m := NewMsg()
		if err := m.Bcc(a...); err != nil {
			t.Errorf("failed to set BCC addresses: %s", err)
			return
		}
		if err := m.AddBccFormat(nn, na); err != nil {
			t.Errorf("AddBccFormat failed: %s", err)
			return
		}

		atf := false
		for _, v := range m.addrHeader[HeaderBcc] {
			if v.String() == w {
				atf = true
			}
		}
		if !atf {
			t.Errorf("AddBccFormat() failed. Address %q not found in BCC address slice.", w)
		}
	}

// TestMsg_BccIgnoreInvalid tests the Msg.BccIgnoreInvalid method

	func TestMsg_BccIgnoreInvalid(t *testing.T) {
		a := []string{"address1@example.com", "address2@example.com"}
		fa := []string{"address1@example.com", "address2@example.com", "failedaddress.com"}
		m := NewMsg()

		m.BccIgnoreInvalid(a...)
		l := len(m.addrHeader[HeaderBcc])
		if l != len(a) {
			t.Errorf("BccIgnoreInvalid() failed. Expected %d addresses, got: %d", len(a), l)
		}
		m.BccIgnoreInvalid(fa...)
		l = len(m.addrHeader[HeaderBcc])
		if l != len(fa)-1 {
			t.Errorf("BccIgnoreInvalid() failed. Expected %d addresses, got: %d", len(fa)-1, l)
		}
	}

// TestMsg_SetBulk tests the Msg.SetBulk method

	func TestMsg_SetBulk(t *testing.T) {
		m := NewMsg()
		m.SetBulk()
		if m.genHeader[HeaderPrecedence] == nil {
			t.Errorf("SetBulk() failed. Precedence header is nil")
			return
		}
		if m.genHeader[HeaderPrecedence][0] != "bulk" {
			t.Errorf("SetBulk() failed. Expected Precedence header: %q, got: %q", "bulk",
				m.genHeader[HeaderPrecedence][0])
		}
		if m.genHeader[HeaderXAutoResponseSuppress] == nil {
			t.Errorf("SetBulk() failed. X-Auto-Response-Suppress header is nil")
			return
		}
		if m.genHeader[HeaderXAutoResponseSuppress][0] != "All" {
			t.Errorf("SetBulk() failed. Expected X-Auto-Response-Suppress header: %q, got: %q", "All",
				m.genHeader[HeaderXAutoResponseSuppress][0])
		}
	}

// TestMsg_SetDate tests the Msg.SetDate and Msg.SetDateWithValue method

	func TestMsg_SetDate(t *testing.T) {
		m := NewMsg()
		m.SetDate()
		if m.genHeader[HeaderDate] == nil {
			t.Errorf("SetDate() failed. Date header is nil")
			return
		}
		d, ok := m.genHeader[HeaderDate]
		if !ok {
			t.Errorf("failed to get date header")
			return
		}
		_, err := time.Parse(time.RFC1123Z, d[0])
		if err != nil {
			t.Errorf("failed to parse time in date header: %s", err)
		}
		m.genHeader = nil
		m.genHeader = make(map[Header][]string)

		now := time.Now()
		m.SetDateWithValue(now)
		if m.genHeader[HeaderDate] == nil {
			t.Errorf("SetDateWithValue() failed. Date header is nil")
			return
		}
		d, ok = m.genHeader[HeaderDate]
		if !ok {
			t.Errorf("failed to get date header")
			return
		}
		pt, err := time.Parse(time.RFC1123Z, d[0])
		if err != nil {
			t.Errorf("failed to parse time in date header: %s", err)
		}
		if pt.Unix() != now.Unix() {
			t.Errorf("SetDateWithValue() failed. Expected time: %d, got: %d", now.Unix(),
				pt.Unix())
		}
	}

// TestMsg_SetMessageIDWIthValue tests the Msg.SetMessageIDWithValue and Msg.SetMessageID methods

	func TestMsg_SetMessageIDWithValue(t *testing.T) {
		m := NewMsg()
		m.SetMessageID()
		if m.genHeader[HeaderMessageID] == nil {
			t.Errorf("SetMessageID() failed. MessageID header is nil")
			return
		}
		if m.genHeader[HeaderMessageID][0] == "" {
			t.Errorf("SetMessageID() failed. Expected value, got: empty")
			return
		}
		if _, ok := m.genHeader[HeaderMessageID]; ok {
			m.genHeader[HeaderMessageID] = nil
		}
		v := "This.is.a.message.id"
		vf := "<This.is.a.message.id>"
		m.SetMessageIDWithValue(v)
		if m.genHeader[HeaderMessageID] == nil {
			t.Errorf("SetMessageIDWithValue() failed. MessageID header is nil")
			return
		}
		if m.genHeader[HeaderMessageID][0] != vf {
			t.Errorf("SetMessageIDWithValue() failed. Expected: %s, got: %s", vf, m.genHeader[HeaderMessageID][0])
			return
		}
	}

// TestMsg_SetMessageIDRandomness tests the randomness of Msg.SetMessageID methods

	func TestMsg_SetMessageIDRandomness(t *testing.T) {
		var mids []string
		m := NewMsg()
		for i := 0; i < 50_000; i++ {
			m.SetMessageID()
			mid := m.GetMessageID()
			mids = append(mids, mid)
		}
		c := make(map[string]int)
		for i := range mids {
			c[mids[i]]++
		}
		for k, v := range c {
			if v > 1 {
				t.Errorf("MessageID randomness not given. MessageID %q was generated %d times", k, v)
			}
		}
	}

	func TestMsg_GetMessageID(t *testing.T) {
		expected := "this.is.a.message.id"
		msg := NewMsg()
		msg.SetMessageIDWithValue(expected)
		val := msg.GetMessageID()
		if !strings.EqualFold(val, fmt.Sprintf("<%s>", expected)) {
			t.Errorf("GetMessageID() failed. Expected: %s, got: %s", fmt.Sprintf("<%s>", expected), val)
		}
		msg.genHeader[HeaderMessageID] = nil
		val = msg.GetMessageID()
		if val != "" {
			t.Errorf("GetMessageID() failed. Expected empty string, got: %s", val)
		}
	}

// TestMsg_FromFormat tests the FromFormat and EnvelopeFrom methods for the Msg object

	func TestMsg_FromFormat(t *testing.T) {
		tests := []struct {
			tname string
			name  string
			addr  string
			want  string
			fail  bool
		}{
			{
				"valid name and addr", "Toni Tester", "tester@example.com",
				`"Toni Tester" <tester@example.com>`, false,
			},
			{
				"no name with valid addr", "", "tester@example.com",
				`<tester@example.com>`, false,
			},
			{
				"valid name with invalid addr", "Toni Tester", "@example.com",
				``, true,
			},
		}

		m := NewMsg()
		for _, tt := range tests {
			t.Run(tt.tname, func(t *testing.T) {
				if err := m.FromFormat(tt.name, tt.addr); err != nil && !tt.fail {
					t.Errorf("failed to FromFormat(): %s", err)
					return
				}
				if err := m.EnvelopeFromFormat(tt.name, tt.addr); err != nil && !tt.fail {
					t.Errorf("failed to EnvelopeFromFormat(): %s", err)
					return
				}

				var fa *mail.Address
				f, ok := m.addrHeader[HeaderFrom]
				if ok && len(f) > 0 {
					fa = f[0]
				}
				if (!ok || len(f) == 0) && !tt.fail {
					t.Errorf(`valid from address expected, but "From:" field is empty`)
					return
				}
				if tt.fail && len(f) > 0 {
					t.Errorf("FromFormat() was supposed to failed but got value: %s", fa.String())
					return
				}

				if !tt.fail && fa.String() != tt.want {
					t.Errorf("wrong result for FromFormat(). Want: %s, got: %s", tt.want, fa.String())
				}
				m.addrHeader[HeaderFrom] = nil
			})
		}
	}

	func TestMsg_GetRecipients(t *testing.T) {
		a := []string{"to@example.com", "cc@example.com", "bcc@example.com"}
		m := NewMsg()

		_, err := m.GetRecipients()
		if err == nil {
			t.Errorf("GetRecipients() succeeded but was expected to fail")
			return
		}

		if err := m.AddTo(a[0]); err != nil {
			t.Errorf("AddTo() failed: %s", err)
			return
		}
		if err := m.AddCc(a[1]); err != nil {
			t.Errorf("AddCc() failed: %s", err)
			return
		}
		if err := m.AddBcc(a[2]); err != nil {
			t.Errorf("AddBcc() failed: %s", err)
			return
		}

		al, err := m.GetRecipients()
		if err != nil {
			t.Errorf("GetRecipients() failed: %s", err)
			return
		}

		tf, cf, bf := false, false, false
		for _, r := range al {
			if r == a[0] {
				tf = true
			}
			if r == a[1] {
				cf = true
			}
			if r == a[2] {
				bf = true
			}
		}
		if !tf {
			t.Errorf("GetRecipients() failed. Expected to address %s but was not found", a[0])
			return
		}
		if !cf {
			t.Errorf("GetRecipients() failed. Expected cc address %s but was not found", a[1])
			return
		}
		if !bf {
			t.Errorf("GetRecipients() failed. Expected bcc address %s but was not found", a[2])
			return
		}
	}

// TestMsg_ReplyTo tests the Msg.ReplyTo and Msg.ReplyToFormat methods

	func TestMsg_ReplyTo(t *testing.T) {
		tests := []struct {
			tname string
			name  string
			addr  string
			want  string
			sf    bool
		}{
			{
				"valid name and addr", "Toni Tester", "tester@example.com",
				`"Toni Tester" <tester@example.com>`, false,
			},
			{
				"no name with valid addr", "", "tester@example.com",
				`<tester@example.com>`, false,
			},
			{
				"valid name with invalid addr", "Toni Tester", "@example.com",
				``, true,
			},
		}
		m := NewMsg()
		for _, tt := range tests {
			t.Run(tt.tname, func(t *testing.T) {
				if err := m.ReplyTo(tt.want); err != nil && !tt.sf {
					t.Errorf("ReplyTo() method failed: %s", err)
				}
				if !tt.sf {
					rt, ok := m.genHeader[HeaderReplyTo]
					if !ok {
						t.Errorf("ReplyTo() failed: ReplyTo generic header not set")
						return
					}
					if len(rt) <= 0 {
						t.Errorf("ReplyTo() failed: length of generic ReplyTo header is zero or less than zero")
						return
					}
					if rt[0] != tt.want {
						t.Errorf("ReplyTo() failed: expected value: %s, got: %s", tt.want, rt[0])
					}
				}
				m.genHeader = nil
				m.genHeader = make(map[Header][]string)
				if err := m.ReplyToFormat(tt.name, tt.addr); err != nil && !tt.sf {
					t.Errorf("ReplyToFormat() method failed: %s", err)
				}
				if !tt.sf {
					rt, ok := m.genHeader[HeaderReplyTo]
					if !ok {
						t.Errorf("ReplyTo() failed: ReplyTo generic header not set")
						return
					}
					if len(rt) <= 0 {
						t.Errorf("ReplyTo() failed: length of generic ReplyTo header is zero or less than zero")
						return
					}
					if rt[0] != tt.want {
						t.Errorf("ReplyTo() failed: expected value: %s, got: %s", tt.want, rt[0])
					}
				}
				m.genHeader = nil
				m.genHeader = make(map[Header][]string)
			})
		}
	}

// TestMsg_Subject tests the Msg.Subject method

	func TestMsg_Subject(t *testing.T) {
		tests := []struct {
			name string
			sub  string
			want string
		}{
			{"normal subject", "This is a test subject", "This is a test subject"},
			{
				"subject with umlauts", "This is a test subject with umlauts: üäöß",
				"=?UTF-8?q?This_is_a_test_subject_with_umlauts:_=C3=BC=C3=A4=C3=B6=C3=9F?=",
			},
			{
				"subject with emoji", "This is a test subject with emoji: 📧",
				"=?UTF-8?q?This_is_a_test_subject_with_emoji:_=F0=9F=93=A7?=",
			},
		}
		m := NewMsg()
		for _, tt := range tests {
			t.Run(tt.name, func(t *testing.T) {
				m.Subject(tt.sub)
				s, ok := m.genHeader[HeaderSubject]
				if !ok || len(s) <= 0 {
					t.Errorf("Subject() method failed. Generic header for Subject is empty")
					return
				}
				if s[0] != tt.want {
					t.Errorf("Subject() method failed. Expected: %s, got: %s", tt.want, s[0])
				}
			})
		}
	}

// TestMsg_SetImportance tests the Msg.SetImportance method

	func TestMsg_SetImportance(t *testing.T) {
		tests := []struct {
			name   string
			imp    Importance
			wantns string
			xprio  string
			want   string
			sf     bool
		}{
			{"Importance: Non-Urgent", ImportanceNonUrgent, "0", "5", "non-urgent", false},
			{"Importance: Low", ImportanceLow, "0", "5", "low", false},
			{"Importance: Normal", ImportanceNormal, "", "", "", true},
			{"Importance: High", ImportanceHigh, "1", "1", "high", false},
			{"Importance: Urgent", ImportanceUrgent, "1", "1", "urgent", false},
			{"Importance: Unknown", 9, "", "", "", true},
		}
		m := NewMsg()
		for _, tt := range tests {
			t.Run(tt.name, func(t *testing.T) {
				m.SetImportance(tt.imp)
				hi, ok := m.genHeader[HeaderImportance]
				if (!ok || len(hi) <= 0) && !tt.sf {
					t.Errorf("SetImportance() method failed. Generic header for Importance is empty")
				}
				hp, ok := m.genHeader[HeaderPriority]
				if (!ok || len(hp) <= 0) && !tt.sf {
					t.Errorf("SetImportance() method failed. Generic header for Priority is empty")
				}
				hx, ok := m.genHeader[HeaderXPriority]
				if (!ok || len(hx) <= 0) && !tt.sf {
					t.Errorf("SetImportance() method failed. Generic header for X-Priority is empty")
				}
				hm, ok := m.genHeader[HeaderXMSMailPriority]
				if (!ok || len(hm) <= 0) && !tt.sf {
					t.Errorf("SetImportance() method failed. Generic header for X-MS-XPriority is empty")
				}
				if !tt.sf {
					if hi[0] != tt.want {
						t.Errorf("SetImportance() method failed. Expected Imporance: %s, got: %s", tt.want, hi[0])
					}
					if hp[0] != tt.wantns {
						t.Errorf("SetImportance() method failed. Expected Priority: %s, got: %s", tt.want, hp[0])
					}
					if hx[0] != tt.xprio {
						t.Errorf("SetImportance() method failed. Expected X-Priority: %s, got: %s", tt.want, hx[0])
					}
					if hm[0] != tt.wantns {
						t.Errorf("SetImportance() method failed. Expected X-MS-Priority: %s, got: %s", tt.wantns, hm[0])
					}
				}
				m.genHeader = nil
				m.genHeader = make(map[Header][]string)
			})
		}
	}

// TestMsg_SetOrganization tests the Msg.SetOrganization method

	func TestMsg_SetOrganization(t *testing.T) {
		tests := []struct {
			name string
			org  string
		}{
			{"Org: testcorp", "testcorp"},
		}
		m := NewMsg()
		for _, tt := range tests {
			t.Run(tt.name, func(t *testing.T) {
				m.SetOrganization(tt.org)
				o, ok := m.genHeader[HeaderOrganization]
				if !ok || len(o) <= 0 {
					t.Errorf("SetOrganization() method failed. Generic header for Organization is empty")
					return
				}
				if o[0] != tt.org {
					t.Errorf("SetOrganization() method failed. Expected: %s, got: %s", tt.org, o[0])
				}
			})
		}
	}

// TestMsg_SetUserAgent tests the Msg.SetUserAgent method

	func TestMsg_SetUserAgent(t *testing.T) {
		tests := []struct {
			name string
			ua   string
		}{
			{"UA: Testmail 1.0", "Testmailer 1.0"},
		}
		m := NewMsg()
		for _, tt := range tests {
			t.Run(tt.name, func(t *testing.T) {
				m.SetUserAgent(tt.ua)
				xm, ok := m.genHeader[HeaderXMailer]
				if !ok || len(xm) <= 0 {
					t.Errorf("SetUserAgent() method failed. Generic header for X-Mailer is empty")
					return
				}
				ua, ok := m.genHeader[HeaderUserAgent]
				if !ok || len(ua) <= 0 {
					t.Errorf("SetUserAgent() method failed. Generic header for UserAgent is empty")
					return
				}
				if xm[0] != tt.ua {
					t.Errorf("SetUserAgent() method failed. Expected X-Mailer: %s, got: %s", tt.ua, xm[0])
				}
				if ua[0] != tt.ua {
					t.Errorf("SetUserAgent() method failed. Expected User-Agent: %s, got: %s", tt.ua, ua[0])
				}
			})
		}
	}

// TestMsg_RequestMDN tests the different RequestMDN* related methods of Msg

	func TestMsg_RequestMDN(t *testing.T) {
		n := "Toni Tester"
		n2 := "Melanie Tester"
		v := "toni.tester@example.com"
		v2 := "melanie.tester@example.com"
		iv := "testertest.tld"
		vl := []string{v, v2}
		m := NewMsg()

		// Single valid address
		if err := m.RequestMDNTo(v); err != nil {
			t.Errorf("RequestMDNTo with a single valid address failed: %s", err)
		}
		if val := m.genHeader[HeaderDispositionNotificationTo]; len(val) > 1 {
			if val[0] != fmt.Sprintf("<%s>", v) {
				t.Errorf("RequestMDNTo with a single valid address failed. Expected: %s, got: %s", v,
					val[0])
			}
		}
		m.Reset()

		// Multiples valid addresses
		if err := m.RequestMDNTo(vl...); err != nil {
			t.Errorf("RequestMDNTo with a multiple valid address failed: %s", err)
		}
		if val := m.genHeader[HeaderDispositionNotificationTo]; len(val) > 0 {
			if val[0] != fmt.Sprintf("<%s>", v) {
				t.Errorf("RequestMDNTo with a multiple valid addresses failed. Expected 0: %s, got 0: %s", v,
					val[0])
			}
		}
		if val := m.genHeader[HeaderDispositionNotificationTo]; len(val) > 1 {
			if val[1] != fmt.Sprintf("<%s>", v2) {
				t.Errorf("RequestMDNTo with a multiple valid addresses failed. Expected 1: %s, got 1: %s", v2,
					val[1])
			}
		}
		m.Reset()

		// Invalid address
		if err := m.RequestMDNTo(iv); err == nil {
			t.Errorf("RequestMDNTo with an invalid address was supposed to failed, but didn't")
		}
		m.Reset()

		// Single valid addresses + AddTo
		if err := m.RequestMDNTo(v); err != nil {
			t.Errorf("RequestMDNTo with a single valid address failed: %s", err)
		}
		if err := m.RequestMDNAddTo(v2); err != nil {
			t.Errorf("RequestMDNAddTo with a valid address failed: %s", err)
		}
		if val := m.genHeader[HeaderDispositionNotificationTo]; len(val) > 1 {
			if val[1] != fmt.Sprintf("<%s>", v2) {
				t.Errorf("RequestMDNTo with a multiple valid addresses failed. Expected 1: %s, got 1: %s", v2,
					val[1])
			}
		}
		m.Reset()

		// Single valid address formated + AddToFromat
		if err := m.RequestMDNToFormat(n, v); err != nil {
			t.Errorf("RequestMDNToFormat with a single valid address failed: %s", err)
		}
		if val := m.genHeader[HeaderDispositionNotificationTo]; len(val) > 0 {
			if val[0] != fmt.Sprintf(`"%s" <%s>`, n, v) {
				t.Errorf(`RequestMDNToFormat with a single valid address failed. Expected: "%s" <%s>, got: %s`, n, v,
					val[0])
			}
		}
		if err := m.RequestMDNAddToFormat(n2, v2); err != nil {
			t.Errorf("RequestMDNAddToFormat with a valid address failed: %s", err)
		}
		if val := m.genHeader[HeaderDispositionNotificationTo]; len(val) > 1 {
			if val[1] != fmt.Sprintf(`"%s" <%s>`, n2, v2) {
				t.Errorf(`RequestMDNAddToFormat with a single valid address failed. Expected: "%s" <%s>, got: %s`, n2, v2,
					val[1])
			}
		}
		m.Reset()

		// Invalid formated address
		if err := m.RequestMDNToFormat(n, iv); err == nil {
			t.Errorf("RequestMDNToFormat with an invalid address was supposed to failed, but didn't")
		}

		// Invalid address AddTo + AddToFormat
		if err := m.RequestMDNAddTo(iv); err == nil {
			t.Errorf("RequestMDNAddTo with an invalid address was supposed to failed, but didn't")
		}
		if err := m.RequestMDNAddToFormat(n, iv); err == nil {
			t.Errorf("RequestMDNAddToFormat with an invalid address was supposed to failed, but didn't")
		}
	}

// TestMsg_SetBodyString tests the Msg.SetBodyString method

	func TestMsg_SetBodyString(t *testing.T) {
		tests := []struct {
			name  string
			ct    ContentType
			value string
			want  string
			sf    bool
		}{
			{"Body: test", TypeTextPlain, "test", "test", false},
			{
				"Body: with Umlauts", TypeTextHTML, "<strong>üäöß</strong>",
				"<strong>üäöß</strong>", false,
			},
			{"Body: with emoji", TypeTextPlain, "📧", "📧", false},
		}
		m := NewMsg()
		for _, tt := range tests {
			t.Run(tt.name, func(t *testing.T) {
				m.SetBodyString(tt.ct, tt.value)
				if len(m.parts) != 1 {
					t.Errorf("SetBodyString() failed: no mail parts found")
				}
				part := m.parts[0]
				res := bytes.Buffer{}
				if _, err := part.writeFunc(&res); err != nil && !tt.sf {
					t.Errorf("WriteFunc of part failed: %s", err)
				}
				if res.String() != tt.want {
					t.Errorf("SetBodyString() failed. Expecteding: %s, got: %s", tt.want, res.String())
				}
			})
		}
	}

// TestMsg_AddAlternativeString tests the Msg.AddAlternativeString method

	func TestMsg_AddAlternativeString(t *testing.T) {
		tests := []struct {
			name  string
			value string
			want  string
			sf    bool
		}{
			{"Body: test", "test", "test", false},
			{"Body: with Umlauts", "<strong>üäöß</strong>", "<strong>üäöß</strong>", false},
			{"Body: with emoji", "📧", "📧", false},
		}
		m := NewMsg()
		for _, tt := range tests {
			t.Run(tt.name, func(t *testing.T) {
				m.SetBodyString(TypeTextPlain, tt.value)
				if len(m.parts) != 1 {
					t.Errorf("AddAlternativeString() => SetBodyString() failed: no mail parts found")
				}
				m.AddAlternativeString(TypeTextHTML, tt.value)
				if len(m.parts) != 2 {
					t.Errorf("AddAlternativeString() failed: no alternative mail parts found")
				}
				apart := m.parts[1]
				res := bytes.Buffer{}
				if _, err := apart.writeFunc(&res); err != nil && !tt.sf {
					t.Errorf("WriteFunc of part failed: %s", err)
				}
				if res.String() != tt.want {
					t.Errorf("AddAlternativeString() failed. Expecteding: %s, got: %s", tt.want, res.String())
				}
			})
		}
	}

// TestMsg_AttachFile tests the Msg.AttachFile and the WithFilename FileOption method

	func TestMsg_AttachFile(t *testing.T) {
		tests := []struct {
			name string
			file string
			fn   string
			sf   bool
		}{
			{"File: README.md", "README.md", "README.md", false},
			{"File: doc.go", "doc.go", "foo.go", false},
			{"File: nonexisting", "", "invalid.file", true},
		}
		m := NewMsg()
		for _, tt := range tests {
			t.Run(tt.name, func(t *testing.T) {
				m.AttachFile(tt.file, WithFileName(tt.fn), nil)
				if len(m.attachments) != 1 && !tt.sf {
					t.Errorf("AttachFile() failed. Number of attachments expected: %d, got: %d", 1,
						len(m.attachments))
					return
				}
				if !tt.sf {
					file := m.attachments[0]
					if file == nil {
						t.Errorf("AttachFile() failed. Attachment file pointer is nil")
						return
					}
					if file.Name != tt.fn {
						t.Errorf("AttachFile() failed. Filename of attachment expected: %s, got: %s", tt.fn,
							file.Name)
					}
					buf := bytes.Buffer{}
					if _, err := file.Writer(&buf); err != nil {
						t.Errorf("failed to execute WriterFunc: %s", err)
						return
					}
				}
				m.Reset()
			})
		}
	}

// TestMsg_GetAttachments tests the Msg.GetAttachments method

	func TestMsg_GetAttachments(t *testing.T) {
		tests := []struct {
			name  string
			files []string
		}{
			{"File: README.md", []string{"README.md"}},
			{"File: doc.go", []string{"doc.go"}},
			{"File: README.md and doc.go", []string{"README.md", "doc.go"}},
			{"File: nonexisting", nil},
		}
		m := NewMsg()
		for _, tt := range tests {
			t.Run(tt.name, func(t *testing.T) {
				for _, f := range tt.files {
					m.AttachFile(f, WithFileName(f), nil)
				}
				if len(m.attachments) != len(tt.files) {
					t.Errorf("AttachFile() failed. Number of attachments expected: %d, got: %d", len(tt.files),
						len(m.attachments))
					return
				}
				ff := m.GetAttachments()
				if len(m.attachments) != len(ff) {
					t.Errorf("GetAttachments() failed. Number of attachments expected: %d, got: %d", len(m.attachments),
						len(ff))
					return
				}
				var fn []string
				for _, f := range ff {
					fn = append(fn, f.Name)
				}
				sort.Strings(fn)
				sort.Strings(tt.files)
				for i, f := range tt.files {
					if f != fn[i] {
						t.Errorf("GetAttachments() failed. Attachment name expected: %s, got: %s", f,
							fn[i])
						return
					}
				}
				m.Reset()
			})
		}
	}

// TestMsg_SetAttachments tests the Msg.GetAttachments method

	func TestMsg_SetAttachments(t *testing.T) {
		tests := []struct {
			name        string
			attachments []string
			files       []string
		}{
			{"File: replace README.md  with doc.go", []string{"README.md"}, []string{"doc.go"}},
			{"File: add README.md with doc.go ", []string{"doc.go"}, []string{"README.md", "doc.go"}},
			{"File: remove README.md and doc.go", []string{"README.md", "doc.go"}, nil},
			{"File: add README.md and doc.go", nil, []string{"README.md", "doc.go"}},
		}
		m := NewMsg()
		for _, tt := range tests {
			t.Run(tt.name, func(t *testing.T) {
				sort.Strings(tt.attachments)
				sort.Strings(tt.files)
				for _, a := range tt.attachments {
					m.AttachFile(a, WithFileName(a), nil)
				}
				if len(m.attachments) != len(tt.attachments) {
					t.Errorf("AttachFile() failed. Number of attachments expected: %d, got: %d", len(tt.files),
						len(m.attachments))
					return
				}
				var files []*File
				for _, f := range tt.files {
					files = append(files, &File{Name: f})
				}
				m.SetAttachments(files)
				if len(m.attachments) != len(files) {
					t.Errorf("SetAttachements() failed. Number of attachments expected: %d, got: %d", len(files),
						len(m.attachments))
					return
				}
				for i, f := range tt.files {
					if f != m.attachments[i].Name {
						t.Errorf("SetAttachments() failed. Attachment name expected: %s, got: %s", f,
							m.attachments[i].Name)
						return
					}
				}
				m.Reset()
			})
		}
	}

// TestMsg_UnsetAllAttachments tests the Msg.UnsetAllAttachments method

	func TestMsg_UnsetAllAttachments(t *testing.T) {
		tests := []struct {
			name        string
			attachments []string
		}{
			{"File: one file", []string{"README.md"}},
			{"File: two files", []string{"README.md", "doc.go"}},
			{"File: nil", nil},
		}
		m := NewMsg()
		for _, tt := range tests {
			t.Run(tt.name, func(t *testing.T) {
				var files []*File
				for _, f := range tt.attachments {
					files = append(files, &File{Name: f})
				}
				m.SetAttachments(files)

				if len(m.attachments) != len(files) {
					t.Errorf("SetAttachements() failed. Number of attachments expected: %d, got: %d", len(files),
						len(m.attachments))
					return
				}
				m.UnsetAllAttachments()
				if m.attachments != nil {
					t.Errorf("UnsetAllAttachments() failed. The attachments file's pointer is not nil")
					return
				}
				m.Reset()
			})
		}
	}

// TestMsg_GetEmbeds tests the Msg.GetEmbeds method

	func TestMsg_GetEmbeds(t *testing.T) {
		tests := []struct {
			name  string
			files []string
		}{
			{"File: README.md", []string{"README.md"}},
			{"File: doc.go", []string{"doc.go"}},
			{"File: README.md and doc.go", []string{"README.md", "doc.go"}},
			{"File: nonexisting", nil},
		}
		m := NewMsg()
		for _, tt := range tests {
			t.Run(tt.name, func(t *testing.T) {
				for _, f := range tt.files {
					m.EmbedFile(f, WithFileName(f), nil)
				}
				if len(m.embeds) != len(tt.files) {
					t.Errorf("EmbedFile() failed. Number of embedded files expected: %d, got: %d", len(tt.files),
						len(m.embeds))
					return
				}
				ff := m.GetEmbeds()
				if len(m.embeds) != len(ff) {
					t.Errorf("GetEmbeds() failed. Number of embedded files expected: %d, got: %d", len(m.embeds),
						len(ff))
					return
				}
				var fn []string
				for _, f := range ff {
					fn = append(fn, f.Name)
				}
				sort.Strings(fn)
				sort.Strings(tt.files)
				for i, f := range tt.files {
					if f != fn[i] {
						t.Errorf("GetEmbeds() failed. Embedded file name expected: %s, got: %s", f,
							fn[i])
						return
					}
				}
				m.Reset()
			})
		}
	}

// TestMsg_SetEmbeds tests the Msg.GetEmbeds method

	func TestMsg_SetEmbeds(t *testing.T) {
		tests := []struct {
			name   string
			embeds []string
			files  []string
		}{
			{"File: replace README.md  with doc.go", []string{"README.md"}, []string{"doc.go"}},
			{"File: add README.md with doc.go ", []string{"doc.go"}, []string{"README.md", "doc.go"}},
			{"File: remove README.md and doc.go", []string{"README.md", "doc.go"}, nil},
			{"File: add README.md and doc.go", nil, []string{"README.md", "doc.go"}},
		}
		m := NewMsg()
		for _, tt := range tests {
			t.Run(tt.name, func(t *testing.T) {
				sort.Strings(tt.embeds)
				sort.Strings(tt.files)
				for _, a := range tt.embeds {
					m.EmbedFile(a, WithFileName(a), nil)
				}
				if len(m.embeds) != len(tt.embeds) {
					t.Errorf("EmbedFile() failed. Number of embedded files expected: %d, got: %d", len(tt.files),
						len(m.embeds))
					return
				}
				var files []*File
				for _, f := range tt.files {
					files = append(files, &File{Name: f})
				}
				m.SetEmbeds(files)
				if len(m.embeds) != len(files) {
					t.Errorf("SetEmbeds() failed. Number of embedded files expected: %d, got: %d", len(files),
						len(m.embeds))
					return
				}
				for i, f := range tt.files {
					if f != m.embeds[i].Name {
						t.Errorf("SetEmbeds() failed. Embedded file name expected: %s, got: %s", f,
							m.embeds[i].Name)
						return
					}
				}
				m.Reset()
			})
		}
	}

// TestMsg_UnsetAllEmbeds tests the Msg.TestMsg_UnsetAllEmbeds method

	func TestMsg_UnsetAllEmbeds(t *testing.T) {
		tests := []struct {
			name   string
			embeds []string
		}{
			{"File: one file", []string{"README.md"}},
			{"File: two files", []string{"README.md", "doc.go"}},
			{"File: nil", nil},
		}
		m := NewMsg()
		for _, tt := range tests {
			t.Run(tt.name, func(t *testing.T) {
				var files []*File
				for _, f := range tt.embeds {
					files = append(files, &File{Name: f})
				}
				m.SetEmbeds(files)
				if len(m.embeds) != len(files) {
					t.Errorf("SetEmbeds() failed. Number of embedded files expected: %d, got: %d", len(files),
						len(m.embeds))
					return
				}
				m.UnsetAllEmbeds()
				if m.embeds != nil {
					t.Errorf("UnsetAllEmbeds() failed. The embeds file's point is not nil")
					return
				}
				m.Reset()
			})
		}
	}

// TestMsg_UnsetAllParts tests the Msg.TestMsg_UnsetAllParts method

	func TestMsg_UnsetAllParts(t *testing.T) {
		tests := []struct {
			name        string
			attachments []string
			embeds      []string
		}{
			{"File: both is exist", []string{"README.md"}, []string{"doc.go"}},
			{"File: both is nil", nil, nil},
			{"File: attachment exist, embed nil", []string{"README.md"}, nil},
			{"File: attachment nil, embed exist", nil, []string{"README.md"}},
		}
		m := NewMsg()
		for _, tt := range tests {
			t.Run(tt.name, func(t *testing.T) {
				var attachments []*File
				for _, f := range tt.attachments {
					attachments = append(attachments, &File{Name: f})
				}
				m.SetAttachments(attachments)
				if len(m.attachments) != len(attachments) {
					t.Errorf("SetAttachements() failed. Number of attachments files expected: %d, got: %d",
						len(attachments), len(m.attachments))
					return
				}
				var embeds []*File
				for _, f := range tt.embeds {
					embeds = append(embeds, &File{Name: f})
				}
				m.SetEmbeds(embeds)
				if len(m.embeds) != len(embeds) {
					t.Errorf("SetEmbeds() failed. Number of embedded files expected: %d, got: %d", len(embeds),
						len(m.embeds))
					return
				}
				m.UnsetAllParts()
				if m.attachments != nil {
					t.Errorf("UnsetAllParts() failed. The attachments file's point is not nil")
					return
				}
				if m.embeds != nil {
					t.Errorf("UnsetAllParts() failed. The embeds file's point is not nil")
					return
				}
				m.Reset()
			})
		}
	}

// TestMsg_AttachFromEmbedFS tests the Msg.AttachFromEmbedFS and the WithFilename FileOption method

	func TestMsg_AttachFromEmbedFS(t *testing.T) {
		tests := []struct {
			name string
			file string
			fn   string
			sf   bool
		}{
			{"File: README.md", "README.md", "README.md", false},
			{"File: nonexisting", "", "invalid.file", true},
		}
		m := NewMsg()
		for _, tt := range tests {
			t.Run(tt.name, func(t *testing.T) {
				if err := m.AttachFromEmbedFS(tt.file, &efs, WithFileName(tt.fn)); err != nil && !tt.sf {
					t.Errorf("AttachFromEmbedFS() failed: %s", err)
					return
				}
				if len(m.attachments) != 1 && !tt.sf {
					t.Errorf("AttachFile() failed. Number of attachments expected: %d, got: %d", 1,
						len(m.attachments))
					return
				}
				if !tt.sf {
					file := m.attachments[0]
					if file == nil {
						t.Errorf("AttachFile() failed. Attachment file pointer is nil")
						return
					}
					if file.Name != tt.fn {
						t.Errorf("AttachFile() failed. Filename of attachment expected: %s, got: %s", tt.fn,
							file.Name)
					}
					buf := bytes.Buffer{}
					if _, err := file.Writer(&buf); err != nil {
						t.Errorf("failed to execute WriterFunc: %s", err)
						return
					}
				}
				m.Reset()
			})
		}
	}

// TestMsg_AttachFileBrokenFunc tests WriterFunc of the Msg.AttachFile  method

	func TestMsg_AttachFileBrokenFunc(t *testing.T) {
		m := NewMsg()
		m.AttachFile("README.md")
		if len(m.attachments) != 1 {
			t.Errorf("AttachFile() failed. Number of attachments expected: %d, got: %d", 1,
				len(m.attachments))
			return
		}
		file := m.attachments[0]
		if file == nil {
			t.Errorf("AttachFile() failed. Attachment file pointer is nil")
			return
		}
		file.Writer = func(io.Writer) (int64, error) {
			return 0, fmt.Errorf("failing intentionally")
		}
		buf := bytes.Buffer{}
		if _, err := file.Writer(&buf); err == nil {
			t.Errorf("execute WriterFunc did not fail, but was expected to fail")
		}
	}

// TestMsg_AttachReader tests the Msg.AttachReader method

	func TestMsg_AttachReader(t *testing.T) {
		m := NewMsg()
		ts := "This is a test string"
		rbuf := bytes.Buffer{}
		rbuf.WriteString(ts)
		r := bufio.NewReader(&rbuf)
		if err := m.AttachReader("testfile.txt", r); err != nil {
			t.Errorf("AttachReader() failed. Expected no error, got: %s", err.Error())
			return
		}
		if len(m.attachments) != 1 {
			t.Errorf("AttachReader() failed. Number of attachments expected: %d, got: %d", 1,
				len(m.attachments))
			return
		}
		file := m.attachments[0]
		if file == nil {
			t.Errorf("AttachReader() failed. Attachment file pointer is nil")
			return
		}
		if file.Name != "testfile.txt" {
			t.Errorf("AttachReader() failed. Expected file name: %s, got: %s", "testfile.txt",
				file.Name)
		}
		wbuf := bytes.Buffer{}
		if _, err := file.Writer(&wbuf); err != nil {
			t.Errorf("execute WriterFunc failed: %s", err)
		}
		if wbuf.String() != ts {
			t.Errorf("AttachReader() failed. Expected string: %q, got: %q", ts, wbuf.String())
		}
	}

// TestMsg_EmbedFile tests the Msg.EmbedFile and the WithFilename FileOption method

	func TestMsg_EmbedFile(t *testing.T) {
		tests := []struct {
			name string
			file string
			fn   string
			sf   bool
		}{
			{"File: README.md", "README.md", "README.md", false},
			{"File: doc.go", "doc.go", "foo.go", false},
			{"File: nonexisting", "", "invalid.file", true},
		}
		m := NewMsg()
		for _, tt := range tests {
			t.Run(tt.name, func(t *testing.T) {
				m.EmbedFile(tt.file, WithFileName(tt.fn), nil)
				if len(m.embeds) != 1 && !tt.sf {
					t.Errorf("EmbedFile() failed. Number of embeds expected: %d, got: %d", 1,
						len(m.embeds))
					return
				}
				if !tt.sf {
					file := m.embeds[0]
					if file == nil {
						t.Errorf("EmbedFile() failed. Embedded file pointer is nil")
						return
					}
					if file.Name != tt.fn {
						t.Errorf("EmbedFile() failed. Filename of embeds expected: %s, got: %s", tt.fn,
							file.Name)
					}
					buf := bytes.Buffer{}
					if _, err := file.Writer(&buf); err != nil {
						t.Errorf("failed to execute WriterFunc: %s", err)
						return
					}
				}
				m.Reset()
			})
		}
	}

// TestMsg_EmbedFromEmbedFS tests the Msg.EmbedFromEmbedFS and the WithFilename FileOption method

	func TestMsg_EmbedFromEmbedFS(t *testing.T) {
		tests := []struct {
			name string
			file string
			fn   string
			sf   bool
		}{
			{"File: README.md", "README.md", "README.md", false},
			{"File: nonexisting", "", "invalid.file", true},
		}
		m := NewMsg()
		for _, tt := range tests {
			t.Run(tt.name, func(t *testing.T) {
				if err := m.EmbedFromEmbedFS(tt.file, &efs, WithFileName(tt.fn)); err != nil && !tt.sf {
					t.Errorf("EmbedFromEmbedFS() failed: %s", err)
					return
				}
				if len(m.embeds) != 1 && !tt.sf {
					t.Errorf("EmbedFile() failed. Number of embeds expected: %d, got: %d", 1,
						len(m.embeds))
					return
				}
				if !tt.sf {
					file := m.embeds[0]
					if file == nil {
						t.Errorf("EmbedFile() failed. Embedded file pointer is nil")
						return
					}
					if file.Name != tt.fn {
						t.Errorf("EmbedFile() failed. Filename of embeds expected: %s, got: %s", tt.fn,
							file.Name)
					}
					buf := bytes.Buffer{}
					if _, err := file.Writer(&buf); err != nil {
						t.Errorf("failed to execute WriterFunc: %s", err)
						return
					}
				}
				m.Reset()
			})
		}
	}

// TestMsg_EmbedFileBrokenFunc tests WriterFunc of the Msg.EmbedFile  method

	func TestMsg_EmbedFileBrokenFunc(t *testing.T) {
		m := NewMsg()
		m.EmbedFile("README.md")
		if len(m.embeds) != 1 {
			t.Errorf("EmbedFile() failed. Number of embeds expected: %d, got: %d", 1,
				len(m.embeds))
			return
		}
		file := m.embeds[0]
		if file == nil {
			t.Errorf("EmbedFile() failed. Embedded file pointer is nil")
			return
		}
		file.Writer = func(io.Writer) (int64, error) {
			return 0, fmt.Errorf("failing intentionally")
		}
		buf := bytes.Buffer{}
		if _, err := file.Writer(&buf); err == nil {
			t.Errorf("execute WriterFunc did not fail, but was expected to fail")
		}
	}

// TestMsg_EmbedReader tests the Msg.EmbedReader method

	func TestMsg_EmbedReader(t *testing.T) {
		m := NewMsg()
		ts := "This is a test string"
		rbuf := bytes.Buffer{}
		rbuf.WriteString(ts)
		r := bufio.NewReader(&rbuf)
		if err := m.EmbedReader("testfile.txt", r); err != nil {
			t.Errorf("EmbedReader() failed. Expected no error, got: %s", err.Error())
			return
		}
		if len(m.embeds) != 1 {
			t.Errorf("EmbedReader() failed. Number of embeds expected: %d, got: %d", 1,
				len(m.embeds))
			return
		}
		file := m.embeds[0]
		if file == nil {
			t.Errorf("EmbedReader() failed. Embedded file pointer is nil")
			return
		}
		if file.Name != "testfile.txt" {
			t.Errorf("EmbedReader() failed. Expected file name: %s, got: %s", "testfile.txt",
				file.Name)
		}
		wbuf := bytes.Buffer{}
		if _, err := file.Writer(&wbuf); err != nil {
			t.Errorf("execute WriterFunc failed: %s", err)
		}
		if wbuf.String() != ts {
			t.Errorf("EmbedReader() failed. Expected string: %q, got: %q", ts, wbuf.String())
		}
	}

// TestMsg_hasAlt tests the hasAlt() method of the Msg

	func TestMsg_hasAlt(t *testing.T) {
		m := NewMsg()
		m.SetBodyString(TypeTextPlain, "Plain")
		m.AddAlternativeString(TypeTextHTML, "<b>HTML</b>")
		if !m.hasAlt() {
			t.Errorf("mail has alternative parts but hasAlt() returned true")
		}
	}

// TestMsg_hasRelated tests the hasRelated() method of the Msg

	func TestMsg_hasRelated(t *testing.T) {
		m := NewMsg()
		m.SetBodyString(TypeTextPlain, "Plain")
		m.EmbedFile("README.md")
		if !m.hasRelated() {
			t.Errorf("mail has related parts but hasRelated() returned true")
		}
	}

// TestMsg_hasMixed tests the hasMixed() method of the Msg

	func TestMsg_hasMixed(t *testing.T) {
		m := NewMsg()
		m.SetBodyString(TypeTextPlain, "Plain")
		m.AttachFile("README.md")
		if !m.hasMixed() {
			t.Errorf("mail has mixed parts but hasMixed() returned true")
		}
	}

// TestMsg_WriteTo tests the WriteTo() method of the Msg

	func TestMsg_WriteTo(t *testing.T) {
		m := NewMsg()
		m.SetBodyString(TypeTextPlain, "Plain")
		wbuf := bytes.Buffer{}
		n, err := m.WriteTo(&wbuf)
		if err != nil {
			t.Errorf("WriteTo() failed: %s", err)
			return
		}
		if n != int64(wbuf.Len()) {
			t.Errorf("WriteTo() failed: expected written byte length: %d, got: %d", n, wbuf.Len())
		}
	}

// TestMsg_WriteToSkipMiddleware tests the WriteTo() method of the Msg

	func TestMsg_WriteToSkipMiddleware(t *testing.T) {
		m := NewMsg(WithMiddleware(encodeMiddleware{}), WithMiddleware(uppercaseMiddleware{}))
		m.Subject("This is a test")
		m.SetBodyString(TypeTextPlain, "Plain")
		wbuf := bytes.Buffer{}
		n, err := m.WriteToSkipMiddleware(&wbuf, "uppercase")
		if err != nil {
			t.Errorf("WriteToSkipMiddleware() failed: %s", err)
			return
		}
		if n != int64(wbuf.Len()) {
			t.Errorf("WriteToSkipMiddleware() failed: expected written byte length: %d, got: %d", n, wbuf.Len())
		}
		if !strings.Contains(wbuf.String(), "Subject: This is @ test") {
			t.Errorf("WriteToSkipMiddleware failed. Unable to find encoded subject")
		}

		wbuf2 := bytes.Buffer{}
		n, err = m.WriteTo(&wbuf2)
		if err != nil {
			t.Errorf("WriteTo() failed: %s", err)
			return
		}
		if n != int64(wbuf2.Len()) {
			t.Errorf("WriteTo() failed: expected written byte length: %d, got: %d", n, wbuf2.Len())
		}
		if !strings.Contains(wbuf2.String(), "Subject: THIS IS @ TEST") {
			t.Errorf("WriteToSkipMiddleware failed. Unable to find encoded and upperchase subject")
		}
	}

// TestMsg_WriteTo_fails tests the WriteTo() method of the Msg but with a failing body writer function

	func TestMsg_WriteTo_fails(t *testing.T) {
		m := NewMsg()
		m.SetBodyWriter(TypeTextPlain, func(io.Writer) (int64, error) {
			return 0, errors.New("failed")
		})
		_, err := m.WriteTo(io.Discard)
		if err == nil {
			t.Errorf("WriteTo() with failing BodyWriter function was supposed to fail, but didn't")
			return
		}

		// NoEncoding handles the errors separately
		m = NewMsg(WithEncoding(NoEncoding))
		m.SetBodyWriter(TypeTextPlain, func(io.Writer) (int64, error) {
			return 0, errors.New("failed")
		})
		_, err = m.WriteTo(io.Discard)
		if err == nil {
			t.Errorf("WriteTo() (no encoding) with failing BodyWriter function was supposed to fail, but didn't")
			return
		}
	}

// TestMsg_Write tests the Write() method of the Msg

	func TestMsg_Write(t *testing.T) {
		m := NewMsg()
		m.SetBodyString(TypeTextPlain, "Plain")
		wbuf := bytes.Buffer{}
		n, err := m.Write(&wbuf)
		if err != nil {
			t.Errorf("WriteTo() failed: %s", err)
			return
		}
		if n != int64(wbuf.Len()) {
			t.Errorf("WriteTo() failed: expected written byte length: %d, got: %d", n, wbuf.Len())
		}
	}

// TestMsg_WriteWithLongHeader tests the WriteTo() method of the Msg with a long header

	func TestMsg_WriteWithLongHeader(t *testing.T) {
		m := NewMsg()
		m.SetBodyString(TypeTextPlain, "Plain")
		m.SetGenHeader(HeaderContentLang, "de", "en", "fr", "es", "xxxx", "yyyy", "de", "en", "fr",
			"es", "xxxx", "yyyy", "de", "en", "fr", "es", "xxxx", "yyyy", "de", "en", "fr")
		m.SetGenHeader(HeaderContentID, "XXXXXXXXXXXXXXX XXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXX",
			"XXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXX")
		wbuf := bytes.Buffer{}
		n, err := m.WriteTo(&wbuf)
		if err != nil {
			t.Errorf("WriteTo() failed: %s", err)
			return
		}
		if n != int64(wbuf.Len()) {
			t.Errorf("WriteTo() failed: expected written byte length: %d, got: %d", n, wbuf.Len())
		}
	}

// TestMsg_WriteDiffEncoding tests the WriteTo() method of the Msg with different Encoding

	func TestMsg_WriteDiffEncoding(t *testing.T) {
		tests := []struct {
			name string
			ct   ContentType
			en   Encoding
			alt  bool
			wa   bool
			we   bool
		}{
			{"Plain/QP/NoAlt/NoAttach/NoEmbed", TypeTextPlain, EncodingQP, false, false, false},
			{"Plain/B64/NoAlt/NoAttach/NoEmbed", TypeTextPlain, EncodingB64, false, false, false},
			{"Plain/No/NoAlt/NoAttach/NoEmbed", TypeTextPlain, NoEncoding, false, false, false},
			{"HTML/QP/NoAlt/NoAttach/NoEmbed", TypeTextHTML, EncodingQP, false, false, false},
			{"HTML/B64/NoAlt/NoAttach/NoEmbed", TypeTextHTML, EncodingB64, false, false, false},
			{"HTML/No/NoAlt/NoAttach/NoEmbed", TypeTextHTML, NoEncoding, false, false, false},
			{"Plain/QP/HTML/NoAttach/NoEmbed", TypeTextPlain, EncodingQP, true, false, false},
			{"Plain/B64/HTML/NoAttach/NoEmbed", TypeTextPlain, EncodingB64, true, false, false},
			{"Plain/No/HTML/NoAttach/NoEmbed", TypeTextPlain, NoEncoding, true, false, false},
			{"Plain/QP/NoAlt/Attach/NoEmbed", TypeTextPlain, EncodingQP, false, true, false},
			{"Plain/B64/NoAlt/Attach/NoEmbed", TypeTextPlain, EncodingB64, false, true, false},
			{"Plain/No/NoAlt/Attach/NoEmbed", TypeTextPlain, NoEncoding, false, true, false},
			{"Plain/QP/NoAlt/NoAttach/Embed", TypeTextPlain, EncodingQP, false, false, true},
			{"Plain/B64/NoAlt/NoAttach/Embed", TypeTextPlain, EncodingB64, false, false, true},
			{"Plain/No/NoAlt/NoAttach/Embed", TypeTextPlain, NoEncoding, false, false, true},
			{"Plain/QP/HTML/Attach/Embed", TypeTextPlain, EncodingQP, true, true, true},
			{"Plain/B64/HTML/Attach/Embed", TypeTextPlain, EncodingB64, true, true, true},
			{"Plain/No/HTML/Attach/Embed", TypeTextPlain, NoEncoding, true, true, true},
		}
		for _, tt := range tests {
			t.Run(tt.name, func(t *testing.T) {
				m := NewMsg(WithEncoding(tt.en))
				m.SetBodyString(tt.ct, tt.name)
				if tt.alt {
					m.AddAlternativeString(TypeTextHTML, fmt.Sprintf("<p>%s</p>", tt.name))
				}
				if tt.wa {
					m.AttachFile("README.md")
				}
				if tt.we {
					m.EmbedFile("README.md")
				}
				wbuf := bytes.Buffer{}
				n, err := m.WriteTo(&wbuf)
				if err != nil {
					t.Errorf("WriteTo() failed: %s", err)
					return
				}
				if n != int64(wbuf.Len()) {
					t.Errorf("WriteTo() failed: expected written byte length: %d, got: %d", n, wbuf.Len())
				}
				wbuf.Reset()
			})
		}
	}

// TestMsg_appendFile tests the appendFile() method of the Msg

	func TestMsg_appendFile(t *testing.T) {
		m := NewMsg()
		var fl []*File
		f := &File{
			Name: "file.txt",
		}
		fl = m.appendFile(fl, f, nil)
		if len(fl) != 1 {
			t.Errorf("appendFile() failed. Expected length: %d, got: %d", 1, len(fl))
		}
		fl = m.appendFile(fl, f, nil)
		if len(fl) != 2 {
			t.Errorf("appendFile() failed. Expected length: %d, got: %d", 2, len(fl))
		}
	}

// TestMsg_multipleWrites tests multiple executions of WriteTo on the Msg

	func TestMsg_multipleWrites(t *testing.T) {
		ts := "XXX_UNIQUE_STRING_XXX"
		wbuf := bytes.Buffer{}
		m := NewMsg()
		m.SetBodyString(TypeTextPlain, ts)

		// First WriteTo()
		_, err := m.WriteTo(&wbuf)
		if err != nil {
			t.Errorf("failed to write body to buffer: %s", err)
		}
		if !strings.Contains(wbuf.String(), ts) {
			t.Errorf("first WriteTo() body does not contain unique string: %s", ts)
		}

		// Second WriteTo()
		wbuf.Reset()
		_, err = m.WriteTo(&wbuf)
		if err != nil {
			t.Errorf("failed to write body to buffer: %s", err)
		}
		if !strings.Contains(wbuf.String(), ts) {
			t.Errorf("second WriteTo() body does not contain unique string: %s", ts)
		}
	}

// TestMsg_NewReader tests the Msg.NewReader method

	func TestMsg_NewReader(t *testing.T) {
		m := NewMsg()
		m.SetBodyString(TypeTextPlain, "TEST123")
		mr := m.NewReader()
		if mr == nil {
			t.Errorf("NewReader failed: Reader is nil")
		}
		if mr.Error() != nil {
			t.Errorf("NewReader failed: %s", mr.Error())
		}
	}

// TestMsg_NewReader_ioCopy tests the Msg.NewReader method using io.Copy

	func TestMsg_NewReader_ioCopy(t *testing.T) {
		wbuf1 := bytes.Buffer{}
		wbuf2 := bytes.Buffer{}
		m := NewMsg()
		m.SetBodyString(TypeTextPlain, "TEST123")
		mr := m.NewReader()
		if mr == nil {
			t.Errorf("NewReader failed: Reader is nil")
		}

		// First we use WriteTo to have something to compare to
		_, err := m.WriteTo(&wbuf1)
		if err != nil {
			t.Errorf("failed to write body to buffer: %s", err)
		}

		// Then we write to wbuf2 via io.Copy
		n, err := io.Copy(&wbuf2, mr)
		if err != nil {
			t.Errorf("failed to use io.Copy on Reader: %s", err)
		}
		if n != int64(wbuf1.Len()) {
			t.Errorf("message length of WriteTo and io.Copy differ. Expected: %d, got: %d", wbuf1.Len(), n)
		}
		if wbuf1.String() != wbuf2.String() {
			t.Errorf("message content of WriteTo and io.Copy differ")
		}
	}

// TestMsg_UpdateReader tests the Msg.UpdateReader method

	func TestMsg_UpdateReader(t *testing.T) {
		m := NewMsg()
		m.Subject("Subject-Run 1")
		mr := m.NewReader()
		if mr == nil {
			t.Errorf("NewReader failed: Reader is nil")
		}
		wbuf1 := bytes.Buffer{}
		_, err := io.Copy(&wbuf1, mr)
		if err != nil {
			t.Errorf("io.Copy on Reader failed: %s", err)
		}
		if !strings.Contains(wbuf1.String(), "Subject: Subject-Run 1") {
			t.Errorf("io.Copy on Reader failed. Expected to find %q but string in Subject was not found",
				"Subject-Run 1")
		}

		m.Subject("Subject-Run 2")
		m.UpdateReader(mr)
		wbuf2 := bytes.Buffer{}
		_, err = io.Copy(&wbuf2, mr)
		if err != nil {
			t.Errorf("2nd io.Copy on Reader failed: %s", err)
		}
		if !strings.Contains(wbuf2.String(), "Subject: Subject-Run 2") {
			t.Errorf("io.Copy on Reader failed. Expected to find %q but string in Subject was not found",
				"Subject-Run 2")
		}
	}

// TestMsg_SetBodyTextTemplate tests the Msg.SetBodyTextTemplate method

	func TestMsg_SetBodyTextTemplate(t *testing.T) {
		tests := []struct {
			name string
			tpl  string
			ph   string
			sf   bool
		}{
			{"normal text", "This is a {{.Placeholder}}", "TemplateTest", false},
			{"invalid tpl", "This is a {{ foo .Placeholder}}", "TemplateTest", true},
		}

		for _, tt := range tests {
			t.Run(tt.name, func(t *testing.T) {
				data := struct {
					Placeholder string
				}{Placeholder: tt.ph}
				tpl, err := ttpl.New("test").Parse(tt.tpl)
				if err != nil && !tt.sf {
					t.Errorf("failed to render template: %s", err)
					return
				}
				m := NewMsg()
				if err := m.SetBodyTextTemplate(tpl, data); err != nil && !tt.sf {
					t.Errorf("failed to set template as body: %s", err)
				}

				wbuf := bytes.Buffer{}
				_, err = m.WriteTo(&wbuf)
				if err != nil {
					t.Errorf("failed to write body to buffer: %s", err)
				}
				if !strings.Contains(wbuf.String(), tt.ph) && !tt.sf {
					t.Errorf("SetBodyTextTemplate failed: Body does not contain the expected tpl placeholder: %s", tt.ph)
				}
				m.Reset()
			})
		}
	}

// TestMsg_SetBodyHTMLTemplate tests the Msg.SetBodyHTMLTemplate method

	func TestMsg_SetBodyHTMLTemplate(t *testing.T) {
		tests := []struct {
			name string
			tpl  string
			ph   string
			ex   string
			sf   bool
		}{
			{"normal HTML", "<p>This is a {{.Placeholder}}</p>", "TemplateTest", "TemplateTest", false},
			{
				"HTML with HTML", "<p>This is a {{.Placeholder}}</p>", "<script>alert(1)</script>",
				"&lt;script&gt;alert(1)&lt;/script&gt;", false,
			},
			{"invalid tpl", "<p>This is a {{ foo .Placeholder}}</p>", "TemplateTest", "", true},
		}

		for _, tt := range tests {
			t.Run(tt.name, func(t *testing.T) {
				data := struct {
					Placeholder string
				}{Placeholder: tt.ph}
				tpl, err := htpl.New("test").Parse(tt.tpl)
				if err != nil && !tt.sf {
					t.Errorf("failed to render template: %s", err)
					return
				}
				m := NewMsg()
				if err := m.SetBodyHTMLTemplate(tpl, data); err != nil && !tt.sf {
					t.Errorf("failed to set template as body: %s", err)
				}

				wbuf := bytes.Buffer{}
				_, err = m.WriteTo(&wbuf)
				if err != nil {
					t.Errorf("failed to write body to buffer: %s", err)
				}
				if !strings.Contains(wbuf.String(), tt.ex) && !tt.sf {
					t.Errorf("SetBodyTextTemplate failed: Body does not contain the expected tpl placeholder: %s", tt.ph)
				}
				m.Reset()
			})
		}
	}

// TestMsg_AddAlternativeTextTemplate tests the Msg.AddAlternativeTextTemplate method

	func TestMsg_AddAlternativeTextTemplate(t *testing.T) {
		tests := []struct {
			name string
			tpl  string
			ph   string
			sf   bool
		}{
			{"normal text", "This is a {{.Placeholder}}", "TemplateTest", false},
			{"invalid tpl", "This is a {{ foo .Placeholder}}", "TemplateTest", true},
		}

		for _, tt := range tests {
			t.Run(tt.name, func(t *testing.T) {
				data := struct {
					Placeholder string
				}{Placeholder: tt.ph}
				tpl, err := ttpl.New("test").Parse(tt.tpl)
				if err != nil && !tt.sf {
					t.Errorf("failed to render template: %s", err)
					return
				}
				m := NewMsg()
				m.SetBodyString(TypeTextHTML, "")
				if err := m.AddAlternativeTextTemplate(tpl, data); err != nil && !tt.sf {
					t.Errorf("failed to set template as alternative part: %s", err)
				}

				wbuf := bytes.Buffer{}
				_, err = m.WriteTo(&wbuf)
				if err != nil {
					t.Errorf("failed to write body to buffer: %s", err)
				}
				if !strings.Contains(wbuf.String(), tt.ph) && !tt.sf {
					t.Errorf("SetBodyTextTemplate failed: Body does not contain the expected tpl placeholder: %s", tt.ph)
				}
				m.Reset()
			})
		}
	}

// TestMsg_AddAlternativeHTMLTemplate tests the Msg.AddAlternativeHTMLTemplate method

	func TestMsg_AddAlternativeHTMLTemplate(t *testing.T) {
		tests := []struct {
			name string
			tpl  string
			ph   string
			ex   string
			sf   bool
		}{
			{"normal HTML", "<p>This is a {{.Placeholder}}</p>", "TemplateTest", "TemplateTest", false},
			{
				"HTML with HTML", "<p>This is a {{.Placeholder}}</p>", "<script>alert(1)</script>",
				"&lt;script&gt;alert(1)&lt;/script&gt;", false,
			},
			{"invalid tpl", "<p>This is a {{ foo .Placeholder}}</p>", "TemplateTest", "", true},
		}

		for _, tt := range tests {
			t.Run(tt.name, func(t *testing.T) {
				data := struct {
					Placeholder string
				}{Placeholder: tt.ph}
				tpl, err := htpl.New("test").Parse(tt.tpl)
				if err != nil && !tt.sf {
					t.Errorf("failed to render template: %s", err)
					return
				}
				m := NewMsg()
				m.SetBodyString(TypeTextPlain, "")
				if err := m.AddAlternativeHTMLTemplate(tpl, data); err != nil && !tt.sf {
					t.Errorf("failed to set template as alternative part: %s", err)
				}

				wbuf := bytes.Buffer{}
				_, err = m.WriteTo(&wbuf)
				if err != nil {
					t.Errorf("failed to write body to buffer: %s", err)
				}
				if !strings.Contains(wbuf.String(), tt.ex) && !tt.sf {
					t.Errorf("SetBodyTextTemplate failed: Body does not contain the expected tpl placeholder: %s", tt.ph)
				}
				m.Reset()
			})
		}
	}

// TestMsg_AttachTextTemplate tests the Msg.AttachTextTemplate method

	func TestMsg_AttachTextTemplate(t *testing.T) {
		tests := []struct {
			name string
			tpl  string
			ph   string
			ex   string
			ac   int
			sf   bool
		}{
			{
				"normal text", "This is a {{.Placeholder}}", "TemplateTest",
				"VGhpcyBpcyBhIFRlbXBsYXRlVGVzdA==", 1, false,
			},
			{"invalid tpl", "This is a {{ foo .Placeholder}}", "TemplateTest", "", 0, true},
		}

		for _, tt := range tests {
			t.Run(tt.name, func(t *testing.T) {
				data := struct {
					Placeholder string
				}{Placeholder: tt.ph}
				tpl, err := ttpl.New("test").Parse(tt.tpl)
				if err != nil && !tt.sf {
					t.Errorf("failed to render template: %s", err)
					return
				}
				m := NewMsg()
				m.SetBodyString(TypeTextPlain, "This is the body")
				if err := m.AttachTextTemplate("attachment.txt", tpl, data); err != nil && !tt.sf {
					t.Errorf("failed to attach template: %s", err)
				}

				wbuf := bytes.Buffer{}
				_, err = m.WriteTo(&wbuf)
				if err != nil {
					t.Errorf("failed to write body to buffer: %s", err)
				}
				if !strings.Contains(wbuf.String(), tt.ex) && !tt.sf {
					t.Errorf("SetBodyTextTemplate failed: Body does not contain the expected tpl placeholder: %s", tt.ph)
				}
				if len(m.attachments) != tt.ac {
					t.Errorf("wrong number of attachments. Expected: %d, got: %d", tt.ac, len(m.attachments))
				}
				m.Reset()
			})
		}
	}

// TestMsg_AttachHTMLTemplate tests the Msg.AttachHTMLTemplate method

	func TestMsg_AttachHTMLTemplate(t *testing.T) {
		tests := []struct {
			name string
			tpl  string
			ph   string
			ex   string
			ac   int
			sf   bool
		}{
			{
				"normal HTML", "<p>This is a {{.Placeholder}}</p>", "TemplateTest",
				"PHA+VGhpcyBpcyBhIFRlbXBsYXRlVGVzdDwvcD4=", 1, false,
			},
			{
				"HTML with HTML", "<p>This is a {{.Placeholder}}</p>", "<script>alert(1)</script>",
				"PHA+VGhpcyBpcyBhICZsdDtzY3JpcHQmZ3Q7YWxlcnQoMSkmbHQ7L3NjcmlwdCZndDs8L3A+", 1, false,
			},
			{"invalid tpl", "<p>This is a {{ foo .Placeholder}}</p>", "TemplateTest", "", 0, true},
		}

		for _, tt := range tests {
			t.Run(tt.name, func(t *testing.T) {
				data := struct {
					Placeholder string
				}{Placeholder: tt.ph}
				tpl, err := htpl.New("test").Parse(tt.tpl)
				if err != nil && !tt.sf {
					t.Errorf("failed to render template: %s", err)
					return
				}
				m := NewMsg()
				m.SetBodyString(TypeTextPlain, "")
				if err := m.AttachHTMLTemplate("attachment.html", tpl, data); err != nil && !tt.sf {
					t.Errorf("failed to set template as alternative part: %s", err)
				}

				wbuf := bytes.Buffer{}
				_, err = m.WriteTo(&wbuf)
				if err != nil {
					t.Errorf("failed to write body to buffer: %s", err)
				}
				if !strings.Contains(wbuf.String(), tt.ex) && !tt.sf {
					t.Errorf("SetBodyTextTemplate failed: Body does not contain the expected tpl placeholder: %s", tt.ph)
				}
				if len(m.attachments) != tt.ac {
					t.Errorf("wrong number of attachments. Expected: %d, got: %d", tt.ac, len(m.attachments))
				}
				m.Reset()
			})
		}
	}

// TestMsg_EmbedTextTemplate tests the Msg.EmbedTextTemplate method

	func TestMsg_EmbedTextTemplate(t *testing.T) {
		tests := []struct {
			name string
			tpl  string
			ph   string
			ex   string
			ec   int
			sf   bool
		}{
			{
				"normal text", "This is a {{.Placeholder}}", "TemplateTest",
				"VGhpcyBpcyBhIFRlbXBsYXRlVGVzdA==", 1, false,
			},
			{"invalid tpl", "This is a {{ foo .Placeholder}}", "TemplateTest", "", 0, true},
		}

		for _, tt := range tests {
			t.Run(tt.name, func(t *testing.T) {
				data := struct {
					Placeholder string
				}{Placeholder: tt.ph}
				tpl, err := ttpl.New("test").Parse(tt.tpl)
				if err != nil && !tt.sf {
					t.Errorf("failed to render template: %s", err)
					return
				}
				m := NewMsg()
				m.SetBodyString(TypeTextPlain, "This is the body")
				if err := m.EmbedTextTemplate("attachment.txt", tpl, data); err != nil && !tt.sf {
					t.Errorf("failed to attach template: %s", err)
				}

				wbuf := bytes.Buffer{}
				_, err = m.WriteTo(&wbuf)
				if err != nil {
					t.Errorf("failed to write body to buffer: %s", err)
				}
				if !strings.Contains(wbuf.String(), tt.ex) && !tt.sf {
					t.Errorf("SetBodyTextTemplate failed: Body does not contain the expected tpl placeholder: %s", tt.ph)
				}
				if len(m.embeds) != tt.ec {
					t.Errorf("wrong number of attachments. Expected: %d, got: %d", tt.ec, len(m.attachments))
				}
				m.Reset()
			})
		}
	}

// TestMsg_EmbedHTMLTemplate tests the Msg.EmbedHTMLTemplate method

	func TestMsg_EmbedHTMLTemplate(t *testing.T) {
		tests := []struct {
			name string
			tpl  string
			ph   string
			ex   string
			ec   int
			sf   bool
		}{
			{
				"normal HTML", "<p>This is a {{.Placeholder}}</p>", "TemplateTest",
				"PHA+VGhpcyBpcyBhIFRlbXBsYXRlVGVzdDwvcD4=", 1, false,
			},
			{
				"HTML with HTML", "<p>This is a {{.Placeholder}}</p>", "<script>alert(1)</script>",
				"PHA+VGhpcyBpcyBhICZsdDtzY3JpcHQmZ3Q7YWxlcnQoMSkmbHQ7L3NjcmlwdCZndDs8L3A+", 1, false,
			},
			{"invalid tpl", "<p>This is a {{ foo .Placeholder}}</p>", "TemplateTest", "", 0, true},
		}

		for _, tt := range tests {
			t.Run(tt.name, func(t *testing.T) {
				data := struct {
					Placeholder string
				}{Placeholder: tt.ph}
				tpl, err := htpl.New("test").Parse(tt.tpl)
				if err != nil && !tt.sf {
					t.Errorf("failed to render template: %s", err)
					return
				}
				m := NewMsg()
				m.SetBodyString(TypeTextPlain, "")
				if err := m.EmbedHTMLTemplate("attachment.html", tpl, data); err != nil && !tt.sf {
					t.Errorf("failed to set template as alternative part: %s", err)
				}

				wbuf := bytes.Buffer{}
				_, err = m.WriteTo(&wbuf)
				if err != nil {
					t.Errorf("failed to write body to buffer: %s", err)
				}
				if !strings.Contains(wbuf.String(), tt.ex) && !tt.sf {
					t.Errorf("SetBodyTextTemplate failed: Body does not contain the expected tpl placeholder: %s", tt.ph)
				}
				if len(m.embeds) != tt.ec {
					t.Errorf("wrong number of attachments. Expected: %d, got: %d", tt.ec, len(m.attachments))
				}
				m.Reset()
			})
		}
	}

// TestMsg_WriteToTempFile will test the output to temporary files

	func TestMsg_WriteToTempFile(t *testing.T) {
		m := NewMsg()
		_ = m.From("Toni Tester <tester@example.com>")
		_ = m.To("Ellenor Tester <ellinor@example.com>")
		m.SetBodyString(TypeTextPlain, "This is a test")
		f, err := m.WriteToTempFile()
		if err != nil {
			t.Errorf("failed to write message to temporary output file: %s", err)
		}
		_ = os.Remove(f)
	}

// TestMsg_WriteToFile will test the output to a file

	func TestMsg_WriteToFile(t *testing.T) {
		f, err := os.CreateTemp("", "go-mail-test_*.eml")
		if err != nil {
			t.Errorf("failed to create temporary output file: %s", err)
		}
		defer func() {
			_ = f.Close()
			_ = os.Remove(f.Name())
		}()

		m := NewMsg()
		_ = m.From("Toni Tester <tester@example.com>")
		_ = m.To("Ellenor Tester <ellinor@example.com>")
		m.SetBodyString(TypeTextPlain, "This is a test")
		if err := m.WriteToFile(f.Name()); err != nil {
			t.Errorf("failed to write to output file: %s", err)
		}
		fi, err := os.Stat(f.Name())
		if err != nil {
			t.Errorf("failed to stat output file: %s", err)
		}
		if fi == nil {
			t.Errorf("received empty file handle")
			return
		}
		if fi.Size() <= 0 {
			t.Errorf("output file is expected to contain data but its size is zero")
		}
	}

// TestMsg_GetGenHeader will test the GetGenHeader method of the Msg

	func TestMsg_GetGenHeader(t *testing.T) {
		m := NewMsg()
		m.Subject("this is a test")
		sa := m.GetGenHeader(HeaderSubject)
		if len(sa) <= 0 {
			t.Errorf("GetGenHeader on subject failed. Got empty slice")
			return
		}
		if sa[0] == "" {
			t.Errorf("GetGenHeader on subject failed. Got empty value")
		}
		if sa[0] != "this is a test" {
			t.Errorf("GetGenHeader on subject failed. Expected: %q, got: %q", "this is a test", sa[0])
		}
	}

// TestMsg_GetAddrHeader will test the Msg.GetAddrHeader method

	func TestMsg_GetAddrHeader(t *testing.T) {
		m := NewMsg()
		if err := m.FromFormat("Toni Sender", "sender@example.com"); err != nil {
			t.Errorf("failed to set FROM address: %s", err)
		}
		if err := m.AddToFormat("Toni To", "to@example.com"); err != nil {
			t.Errorf("failed to set TO address: %s", err)
		}
		if err := m.AddCcFormat("Toni Cc", "cc@example.com"); err != nil {
			t.Errorf("failed to set CC address: %s", err)
		}
		if err := m.AddBccFormat("Toni Bcc", "bcc@example.com"); err != nil {
			t.Errorf("failed to set BCC address: %s", err)
		}
		fh := m.GetAddrHeader(HeaderFrom)
		if len(fh) <= 0 {
			t.Errorf("GetAddrHeader on FROM failed. Got empty slice")
			return
		}
		if fh[0].String() == "" {
			t.Errorf("GetAddrHeader on FROM failed. Got empty value")
		}
		if fh[0].String() != `"Toni Sender" <sender@example.com>` {
			t.Errorf("GetAddrHeader on FROM failed. Expected: %q, got: %q",
				`"Toni Sender" <sender@example.com>"`, fh[0].String())
		}
		th := m.GetAddrHeader(HeaderTo)
		if len(th) <= 0 {
			t.Errorf("GetAddrHeader on TO failed. Got empty slice")
			return
		}
		if th[0].String() == "" {
			t.Errorf("GetAddrHeader on TO failed. Got empty value")
		}
		if th[0].String() != `"Toni To" <to@example.com>` {
			t.Errorf("GetAddrHeader on TO failed. Expected: %q, got: %q",
				`"Toni To" <to@example.com>"`, th[0].String())
		}
		ch := m.GetAddrHeader(HeaderCc)
		if len(ch) <= 0 {
			t.Errorf("GetAddrHeader on CC failed. Got empty slice")
			return
		}
		if ch[0].String() == "" {
			t.Errorf("GetAddrHeader on CC failed. Got empty value")
		}
		if ch[0].String() != `"Toni Cc" <cc@example.com>` {
			t.Errorf("GetAddrHeader on CC failed. Expected: %q, got: %q",
				`"Toni Cc" <cc@example.com>"`, ch[0].String())
		}
		bh := m.GetAddrHeader(HeaderBcc)
		if len(bh) <= 0 {
			t.Errorf("GetAddrHeader on BCC failed. Got empty slice")
			return
		}
		if bh[0].String() == "" {
			t.Errorf("GetAddrHeader on BCC failed. Got empty value")
		}
		if bh[0].String() != `"Toni Bcc" <bcc@example.com>` {
			t.Errorf("GetAddrHeader on BCC failed. Expected: %q, got: %q",
				`"Toni Bcc" <bcc@example.com>"`, bh[0].String())
		}
	}

// TestMsg_GetFrom will test the Msg.GetFrom method

	func TestMsg_GetFrom(t *testing.T) {
		m := NewMsg()
		if err := m.FromFormat("Toni Sender", "sender@example.com"); err != nil {
			t.Errorf("failed to set FROM address: %s", err)
		}
		fh := m.GetFrom()
		if len(fh) <= 0 {
			t.Errorf("GetFrom failed. Got empty slice")
			return
		}
		if fh[0].String() == "" {
			t.Errorf("GetFrom failed. Got empty value")
		}
		if fh[0].String() != `"Toni Sender" <sender@example.com>` {
			t.Errorf("GetFrom failed. Expected: %q, got: %q",
				`"Toni Sender" <sender@example.com>"`, fh[0].String())
		}
	}

// TestMsg_GetFromString will test the Msg.GetFromString method

	func TestMsg_GetFromString(t *testing.T) {
		m := NewMsg()
		if err := m.FromFormat("Toni Sender", "sender@example.com"); err != nil {
			t.Errorf("failed to set FROM address: %s", err)
		}
		fh := m.GetFromString()
		if len(fh) <= 0 {
			t.Errorf("GetFromString failed. Got empty slice")
			return
		}
		if fh[0] == "" {
			t.Errorf("GetFromString failed. Got empty value")
		}
		if fh[0] != `"Toni Sender" <sender@example.com>` {
			t.Errorf("GetFromString failed. Expected: %q, got: %q",
				`"Toni Sender" <sender@example.com>"`, fh[0])
		}
	}

// TestMsg_GetTo will test the Msg.GetTo method

	func TestMsg_GetTo(t *testing.T) {
		m := NewMsg()
		if err := m.AddToFormat("Toni To", "to@example.com"); err != nil {
			t.Errorf("failed to set TO address: %s", err)
		}
		fh := m.GetTo()
		if len(fh) <= 0 {
			t.Errorf("GetTo failed. Got empty slice")
			return
		}
		if fh[0].String() == "" {
			t.Errorf("GetTo failed. Got empty value")
		}
		if fh[0].String() != `"Toni To" <to@example.com>` {
			t.Errorf("GetTo failed. Expected: %q, got: %q",
				`"Toni To" <to@example.com>"`, fh[0].String())
		}
	}

// TestMsg_GetToString will test the Msg.GetToString method

	func TestMsg_GetToString(t *testing.T) {
		m := NewMsg()
		if err := m.AddToFormat("Toni To", "to@example.com"); err != nil {
			t.Errorf("failed to set TO address: %s", err)
		}
		fh := m.GetToString()
		if len(fh) <= 0 {
			t.Errorf("GetToString failed. Got empty slice")
			return
		}
		if fh[0] == "" {
			t.Errorf("GetToString failed. Got empty value")
		}
		if fh[0] != `"Toni To" <to@example.com>` {
			t.Errorf("GetToString failed. Expected: %q, got: %q",
				`"Toni To" <to@example.com>"`, fh[0])
		}
	}

// TestMsg_GetCc will test the Msg.GetCc method

	func TestMsg_GetCc(t *testing.T) {
		m := NewMsg()
		if err := m.AddCcFormat("Toni Cc", "cc@example.com"); err != nil {
			t.Errorf("failed to set TO address: %s", err)
		}
		fh := m.GetCc()
		if len(fh) <= 0 {
			t.Errorf("GetCc failed. Got empty slice")
			return
		}
		if fh[0].String() == "" {
			t.Errorf("GetCc failed. Got empty value")
		}
		if fh[0].String() != `"Toni Cc" <cc@example.com>` {
			t.Errorf("GetCc failed. Expected: %q, got: %q",
				`"Toni Cc" <cc@example.com>"`, fh[0].String())
		}
	}

// TestMsg_GetCcString will test the Msg.GetCcString method

	func TestMsg_GetCcString(t *testing.T) {
		m := NewMsg()
		if err := m.AddCcFormat("Toni Cc", "cc@example.com"); err != nil {
			t.Errorf("failed to set TO address: %s", err)
		}
		fh := m.GetCcString()
		if len(fh) <= 0 {
			t.Errorf("GetCcString failed. Got empty slice")
			return
		}
		if fh[0] == "" {
			t.Errorf("GetCcString failed. Got empty value")
		}
		if fh[0] != `"Toni Cc" <cc@example.com>` {
			t.Errorf("GetCcString failed. Expected: %q, got: %q",
				`"Toni Cc" <cc@example.com>"`, fh[0])
		}
	}

// TestMsg_GetBcc will test the Msg.GetBcc method

	func TestMsg_GetBcc(t *testing.T) {
		m := NewMsg()
		if err := m.AddBccFormat("Toni Bcc", "bcc@example.com"); err != nil {
			t.Errorf("failed to set TO address: %s", err)
		}
		fh := m.GetBcc()
		if len(fh) <= 0 {
			t.Errorf("GetBcc failed. Got empty slice")
			return
		}
		if fh[0].String() == "" {
			t.Errorf("GetBcc failed. Got empty value")
		}
		if fh[0].String() != `"Toni Bcc" <bcc@example.com>` {
			t.Errorf("GetBcc failed. Expected: %q, got: %q",
				`"Toni Cc" <bcc@example.com>"`, fh[0].String())
		}
	}

// TestMsg_GetBccString will test the Msg.GetBccString method

	func TestMsg_GetBccString(t *testing.T) {
		m := NewMsg()
		if err := m.AddBccFormat("Toni Bcc", "bcc@example.com"); err != nil {
			t.Errorf("failed to set TO address: %s", err)
		}
		fh := m.GetBccString()
		if len(fh) <= 0 {
			t.Errorf("GetBccString failed. Got empty slice")
			return
		}
		if fh[0] == "" {
			t.Errorf("GetBccString failed. Got empty value")
		}
		if fh[0] != `"Toni Bcc" <bcc@example.com>` {
			t.Errorf("GetBccString failed. Expected: %q, got: %q",
				`"Toni Cc" <bcc@example.com>"`, fh[0])
		}
	}

// TestMsg_GetBoundary will test the Msg.GetBoundary method

	func TestMsg_GetBoundary(t *testing.T) {
		b := "random_boundary_string"
		m := NewMsg()
		if boundary := m.GetBoundary(); boundary != "" {
			t.Errorf("GetBoundary failed. Expected empty string, but got: %s", boundary)
		}
		m = NewMsg(WithBoundary(b))
		if boundary := m.GetBoundary(); boundary != b {
			t.Errorf("GetBoundary failed. Expected boundary: %s, got: %s", b, boundary)
		}
	}

// TestMsg_AttachEmbedReader_consecutive tests the Msg.AttachReader and Msg.EmbedReader
// methods with consecutive calls to Msg.WriteTo to make sure the attachments are not
// lost (see Github issue #110)

	func TestMsg_AttachEmbedReader_consecutive(t *testing.T) {
		ts1 := "This is a test string"
		ts2 := "Another test string"
		m := NewMsg()
		if err := m.AttachReader("attachment.txt", bytes.NewBufferString(ts1)); err != nil {
			t.Errorf("AttachReader() failed. Expected no error, got: %s", err.Error())
			return
		}
		if err := m.EmbedReader("embedded.txt", bytes.NewBufferString(ts2)); err != nil {
			t.Errorf("EmbedReader() failed. Expected no error, got: %s", err.Error())
			return
		}
		obuf1 := &bytes.Buffer{}
		obuf2 := &bytes.Buffer{}
		_, err := m.WriteTo(obuf1)
		if err != nil {
			t.Errorf("WriteTo to first output buffer failed: %s", err)
		}
		_, err = m.WriteTo(obuf2)
		if err != nil {
			t.Errorf("WriteTo to second output buffer failed: %s", err)
		}
		if !strings.Contains(obuf1.String(), "VGhpcyBpcyBhIHRlc3Qgc3RyaW5n") {
			t.Errorf("Expected file attachment string not found in first output buffer")
		}
		if !strings.Contains(obuf2.String(), "VGhpcyBpcyBhIHRlc3Qgc3RyaW5n") {
			t.Errorf("Expected file attachment string not found in second output buffer")
		}
		if !strings.Contains(obuf1.String(), "QW5vdGhlciB0ZXN0IHN0cmluZw==") {
			t.Errorf("Expected embedded file string not found in first output buffer")
		}
		if !strings.Contains(obuf2.String(), "QW5vdGhlciB0ZXN0IHN0cmluZw==") {
			t.Errorf("Expected embded file string not found in second output buffer")
		}
	}

// TestMsg_AttachEmbedReadSeeker_consecutive tests the Msg.AttachReadSeeker and
// Msg.EmbedReadSeeker methods with consecutive calls to Msg.WriteTo to make
// sure the attachments are not lost (see Github issue #110)

	func TestMsg_AttachEmbedReadSeeker_consecutive(t *testing.T) {
		ts1 := []byte("This is a test string")
		ts2 := []byte("Another test string")
		m := NewMsg()
		m.AttachReadSeeker("attachment.txt", bytes.NewReader(ts1))
		m.EmbedReadSeeker("embedded.txt", bytes.NewReader(ts2))
		obuf1 := &bytes.Buffer{}
		obuf2 := &bytes.Buffer{}
		_, err := m.WriteTo(obuf1)
		if err != nil {
			t.Errorf("WriteTo to first output buffer failed: %s", err)
		}
		_, err = m.WriteTo(obuf2)
		if err != nil {
			t.Errorf("WriteTo to second output buffer failed: %s", err)
		}
		if !strings.Contains(obuf1.String(), "VGhpcyBpcyBhIHRlc3Qgc3RyaW5n") {
			t.Errorf("Expected file attachment string not found in first output buffer")
		}
		if !strings.Contains(obuf2.String(), "VGhpcyBpcyBhIHRlc3Qgc3RyaW5n") {
			t.Errorf("Expected file attachment string not found in second output buffer")
		}
		if !strings.Contains(obuf1.String(), "QW5vdGhlciB0ZXN0IHN0cmluZw==") {
			t.Errorf("Expected embedded file string not found in first output buffer")
		}
		if !strings.Contains(obuf2.String(), "QW5vdGhlciB0ZXN0IHN0cmluZw==") {
			t.Errorf("Expected embded file string not found in second output buffer")
		}
	}

// TestMsg_AttachReadSeeker tests the Msg.AttachReadSeeker method

	func TestMsg_AttachReadSeeker(t *testing.T) {
		m := NewMsg()
		ts := []byte("This is a test string")
		r := bytes.NewReader(ts)
		m.AttachReadSeeker("testfile.txt", r)
		if len(m.attachments) != 1 {
			t.Errorf("AttachReadSeeker() failed. Number of attachments expected: %d, got: %d", 1,
				len(m.attachments))
			return
		}
		file := m.attachments[0]
		if file == nil {
			t.Errorf("AttachReadSeeker() failed. Attachment file pointer is nil")
			return
		}
		if file.Name != "testfile.txt" {
			t.Errorf("AttachReadSeeker() failed. Expected file name: %s, got: %s", "testfile.txt",
				file.Name)
		}
		wbuf := bytes.Buffer{}
		if _, err := file.Writer(&wbuf); err != nil {
			t.Errorf("execute WriterFunc failed: %s", err)
		}
		if wbuf.String() != string(ts) {
			t.Errorf("AttachReadSeeker() failed. Expected string: %q, got: %q", ts, wbuf.String())
		}
	}

// TestMsg_EmbedReadSeeker tests the Msg.EmbedReadSeeker method

	func TestMsg_EmbedReadSeeker(t *testing.T) {
		m := NewMsg()
		ts := []byte("This is a test string")
		r := bytes.NewReader(ts)
		m.EmbedReadSeeker("testfile.txt", r)
		if len(m.embeds) != 1 {
			t.Errorf("EmbedReadSeeker() failed. Number of attachments expected: %d, got: %d", 1,
				len(m.embeds))
			return
		}
		file := m.embeds[0]
		if file == nil {
			t.Errorf("EmbedReadSeeker() failed. Embedded file pointer is nil")
			return
		}
		if file.Name != "testfile.txt" {
			t.Errorf("EmbedReadSeeker() failed. Expected file name: %s, got: %s", "testfile.txt",
				file.Name)
		}
		wbuf := bytes.Buffer{}
		if _, err := file.Writer(&wbuf); err != nil {
			t.Errorf("execute WriterFunc failed: %s", err)
		}
		if wbuf.String() != string(ts) {
			t.Errorf("EmbedReadSeeker() failed. Expected string: %q, got: %q", ts, wbuf.String())
		}
	}

// TestMsg_ToFromString tests Msg.ToFromString in different scenarios

	func TestMsg_ToFromString(t *testing.T) {
		tests := []struct {
			n  string
			v  string
			w  []*mail.Address
			sf bool
		}{
			{"valid single address", "test@test.com", []*mail.Address{
				{Name: "", Address: "test@test.com"},
			}, false},
			{
				"valid multiple addresses", "test@test.com,test2@example.com",
				[]*mail.Address{
					{Name: "", Address: "test@test.com"},
					{Name: "", Address: "test2@example.com"},
				},
				false,
			},
			{
				"valid multiple addresses with space and name",
				`test@test.com, "Toni Tester" <test2@example.com>`,
				[]*mail.Address{
					{Name: "", Address: "test@test.com"},
					{Name: "Toni Tester", Address: "test2@example.com"},
				},
				false,
			},
			{
				"invalid and valid multiple addresses", "test@test.com,test2#example.com", nil,
				true,
			},
		}

		for _, tt := range tests {
			t.Run(tt.n, func(t *testing.T) {
				m := NewMsg()
				if err := m.ToFromString(tt.v); err != nil && !tt.sf {
					t.Errorf("Msg.ToFromString failed: %s", err)
					return
				}
				mto := m.GetTo()
				if len(mto) != len(tt.w) {
					t.Errorf("Msg.ToFromString failed, expected len: %d, got: %d", len(tt.w),
						len(mto))
					return
				}
				for i := range mto {
					w := tt.w[i]
					g := mto[i]
					if w.String() != g.String() {
						t.Errorf("Msg.ToFromString failed, expected address: %s, got: %s",
							w.String(), g.String())
					}
				}
			})
		}
	}

// TestMsg_CcFromString tests Msg.CcFromString in different scenarios

	func TestMsg_CcFromString(t *testing.T) {
		tests := []struct {
			n  string
			v  string
			w  []*mail.Address
			sf bool
		}{
			{"valid single address", "test@test.com", []*mail.Address{
				{Name: "", Address: "test@test.com"},
			}, false},
			{
				"valid multiple addresses", "test@test.com,test2@example.com",
				[]*mail.Address{
					{Name: "", Address: "test@test.com"},
					{Name: "", Address: "test2@example.com"},
				},
				false,
			},
			{
				"valid multiple addresses with space and name",
				`test@test.com, "Toni Tester" <test2@example.com>`,
				[]*mail.Address{
					{Name: "", Address: "test@test.com"},
					{Name: "Toni Tester", Address: "test2@example.com"},
				},
				false,
			},
			{
				"invalid and valid multiple addresses", "test@test.com,test2#example.com", nil,
				true,
			},
		}

		for _, tt := range tests {
			t.Run(tt.n, func(t *testing.T) {
				m := NewMsg()
				if err := m.CcFromString(tt.v); err != nil && !tt.sf {
					t.Errorf("Msg.CcFromString failed: %s", err)
					return
				}
				mto := m.GetCc()
				if len(mto) != len(tt.w) {
					t.Errorf("Msg.CcFromString failed, expected len: %d, got: %d", len(tt.w),
						len(mto))
					return
				}
				for i := range mto {
					w := tt.w[i]
					g := mto[i]
					if w.String() != g.String() {
						t.Errorf("Msg.CcFromString failed, expected address: %s, got: %s",
							w.String(), g.String())
					}
				}
			})
		}
	}

// TestMsg_BccFromString tests Msg.BccFromString in different scenarios

	func TestMsg_BccFromString(t *testing.T) {
		tests := []struct {
			n  string
			v  string
			w  []*mail.Address
			sf bool
		}{
			{"valid single address", "test@test.com", []*mail.Address{
				{Name: "", Address: "test@test.com"},
			}, false},
			{
				"valid multiple addresses", "test@test.com,test2@example.com",
				[]*mail.Address{
					{Name: "", Address: "test@test.com"},
					{Name: "", Address: "test2@example.com"},
				},
				false,
			},
			{
				"valid multiple addresses with space and name",
				`test@test.com, "Toni Tester" <test2@example.com>`,
				[]*mail.Address{
					{Name: "", Address: "test@test.com"},
					{Name: "Toni Tester", Address: "test2@example.com"},
				},
				false,
			},
			{
				"invalid and valid multiple addresses", "test@test.com,test2#example.com", nil,
				true,
			},
		}

		for _, tt := range tests {
			t.Run(tt.n, func(t *testing.T) {
				m := NewMsg()
				if err := m.BccFromString(tt.v); err != nil && !tt.sf {
					t.Errorf("Msg.BccFromString failed: %s", err)
					return
				}
				mto := m.GetBcc()
				if len(mto) != len(tt.w) {
					t.Errorf("Msg.BccFromString failed, expected len: %d, got: %d", len(tt.w),
						len(mto))
					return
				}
				for i := range mto {
					w := tt.w[i]
					g := mto[i]
					if w.String() != g.String() {
						t.Errorf("Msg.BccFromString failed, expected address: %s, got: %s",
							w.String(), g.String())
					}
				}
			})
		}
	}

// TestMsg_checkUserAgent tests the checkUserAgent method of the Msg

	func TestMsg_checkUserAgent(t *testing.T) {
		tests := []struct {
			name               string
			noDefaultUserAgent bool
			genHeader          map[Header][]string
			wantUserAgent      string
			sf                 bool
		}{
			{
				name:               "check default user agent",
				noDefaultUserAgent: false,
				wantUserAgent:      fmt.Sprintf("go-mail v%s // https://github.com/wneessen/go-mail", VERSION),
				sf:                 false,
			},
			{
				name:               "check no default user agent",
				noDefaultUserAgent: true,
				wantUserAgent:      "",
				sf:                 true,
			},
			{
				name:               "check if ua and xm is already set",
				noDefaultUserAgent: false,
				genHeader: map[Header][]string{
					HeaderUserAgent: {"custom UA"},
					HeaderXMailer:   {"custom XM"},
				},
				wantUserAgent: "custom UA",
				sf:            false,
			},
		}
		for _, tt := range tests {
			t.Run(tt.name, func(t *testing.T) {
				msg := &Msg{
					noDefaultUserAgent: tt.noDefaultUserAgent,
					genHeader:          tt.genHeader,
				}
				msg.checkUserAgent()
				gotUserAgent := ""
				if val, ok := msg.genHeader[HeaderUserAgent]; ok {
					gotUserAgent = val[0] // Assuming the first one is the needed value
				}
				if gotUserAgent != tt.wantUserAgent && !tt.sf {
					t.Errorf("UserAgent got = %v, want = %v", gotUserAgent, tt.wantUserAgent)
				}
			})
		}
	}

// TestNewMsgWithMIMEVersion tests WithMIMEVersion and Msg.SetMIMEVersion

	func TestNewMsgWithNoDefaultUserAgent(t *testing.T) {
		m := NewMsg(WithNoDefaultUserAgent())
		if m.noDefaultUserAgent != true {
			t.Errorf("WithNoDefaultUserAgent() failed. Expected: %t, got: %t", true, false)
		}
	}

// Fuzzing tests

	func FuzzMsg_Subject(f *testing.F) {
		f.Add("Testsubject")
		f.Add("")
		f.Add("This is a longer test subject.")
		f.Add("Let's add some umlauts: üäöß")
		f.Add("Or even emojis: ☝️💪👍")
		f.Fuzz(func(t *testing.T, data string) {
			m := NewMsg()
			m.Subject(data)
			m.Reset()
		})
	}

	func FuzzMsg_From(f *testing.F) {
		f.Add("Toni Tester <toni@tester.com>")
		f.Add("<tester@example.com>")
		f.Add("mail@server.com")
		f.Fuzz(func(t *testing.T, data string) {
			m := NewMsg()
			if err := m.From(data); err != nil &&
				!strings.Contains(err.Error(), "failed to parse mail address") {
				t.Errorf("failed set set FROM address: %s", err)
			}
			m.Reset()
		})
	}
*/
type uppercaseMiddleware struct{}

func (mw uppercaseMiddleware) Handle(m *Msg) *Msg {
	s, ok := m.genHeader[HeaderSubject]
	if !ok {
		fmt.Println("can't find the subject header")
	}
	if s == nil || len(s) < 1 {
		s = append(s, "")
	}
	m.Subject(strings.ToUpper(s[0]))
	return m
}

func (mw uppercaseMiddleware) Type() MiddlewareType {
	return "uppercase"
}

type encodeMiddleware struct{}

func (mw encodeMiddleware) Handle(m *Msg) *Msg {
	s, ok := m.genHeader[HeaderSubject]
	if !ok {
		fmt.Println("can't find the subject header")
	}
	if s == nil || len(s) < 1 {
		s = append(s, "")
	}
	m.Subject(strings.Replace(s[0], "a", "@", -1))
	return m
}

func (mw encodeMiddleware) Type() MiddlewareType {
	return "encode"
}