Closes #60. Added final test coverage and an additional SetContent method

part.go

@@ -43,6 +43,12 @@ func (p *Part) GetWriteFunc() func(io.Writer) (int64, error) {
 	return p.w
 }
 
+// SetContent overrides the content of the Part with the given string
+func (p *Part) SetContent(c string) {
+	buf := bytes.NewBufferString(c)
+	p.w = writeFuncFromBuffer(buf)
+}
+
 // SetContentType overrides the ContentType of the Part
 func (p *Part) SetContentType(c ContentType) {
 	p.ctype = c

part_test.go

@@ -7,6 +7,8 @@ package mail
 import (
 	"bytes"
 	"fmt"
+	"io"
+	"strings"
 	"testing"
 )
 
@@ -43,6 +45,35 @@ func TestPartEncoding(t *testing.T) {
 	}
 }
 
+// TestPartContentType tests Part.SetContentType
+func TestPart_SetContentType(t *testing.T) {
+	tests := []struct {
+		name string
+		ct   ContentType
+		want string
+	}{
+		{"ContentType: text/plain", TypeTextPlain, "text/plain"},
+		{"ContentType: text/html", TypeTextHTML, "text/html"},
+		{"ContentType: application/json", "application/json", "application/json"},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			m := NewMsg()
+			m.SetBodyString(TypeTextPlain, "This is a test with ümläutß")
+			pl, err := getPartList(m)
+			if err != nil {
+				t.Errorf("failed: %s", err)
+				return
+			}
+			pl[0].SetContentType(tt.ct)
+			ct := pl[0].GetContentType()
+			if string(ct) != tt.want {
+				t.Errorf("SetContentType failed. Got: %s, expected: %s", string(ct), tt.want)
+			}
+		})
+	}
+}
+
 // TestPartEncoding tests Part.GetEncoding
 func TestPart_GetEncoding(t *testing.T) {
 	tests := []struct {
@@ -119,6 +150,97 @@ func TestPart_GetWriteFunc(t *testing.T) {
 	}
 }
 
+// TestPart_GetContent tests Part.GetContent
+func TestPart_GetContent(t *testing.T) {
+	c := "This is a test with ümläutß"
+	m := NewMsg()
+	m.SetBodyString(TypeTextPlain, c)
+	pl, err := getPartList(m)
+	if err != nil {
+		t.Errorf("failed: %s", err)
+		return
+	}
+	cb, err := pl[0].GetContent()
+	if err != nil {
+		t.Errorf("Part.GetContent failed: %s", err)
+	}
+	if string(cb) != c {
+		t.Errorf("Part.GetContent failed. Expected: %s, got: %s", c, string(cb))
+	}
+}
+
+// TestPart_GetContentBroken tests Part.GetContent
+func TestPart_GetContentBroken(t *testing.T) {
+	c := "This is a test with ümläutß"
+	m := NewMsg()
+	m.SetBodyString(TypeTextPlain, c)
+	pl, err := getPartList(m)
+	if err != nil {
+		t.Errorf("failed: %s", err)
+		return
+	}
+	pl[0].w = func(io.Writer) (int64, error) {
+		return 0, fmt.Errorf("broken")
+	}
+	_, err = pl[0].GetContent()
+	if err == nil {
+		t.Errorf("Part.GetContent was supposed to failed, but didn't")
+	}
+}
+
+// TestPart_SetWriteFunc tests Part.SetWriteFunc
+func TestPart_SetWriteFunc(t *testing.T) {
+	c := "This is a test with ümläutß"
+	m := NewMsg()
+	m.SetBodyString(TypeTextPlain, c)
+	pl, err := getPartList(m)
+	if err != nil {
+		t.Errorf("failed: %s", err)
+		return
+	}
+	cb, err := pl[0].GetContent()
+	if err != nil {
+		t.Errorf("Part.GetContent failed: %s", err)
+	}
+	pl[0].SetWriteFunc(func(w io.Writer) (int64, error) {
+		ns := strings.ToUpper(string(cb))
+		buf := bytes.NewBufferString(ns)
+		nb, err := w.Write(buf.Bytes())
+		return int64(nb), err
+	})
+	nc, err := pl[0].GetContent()
+	if err != nil {
+		t.Errorf("Part.GetContent failed: %s", err)
+	}
+	if string(nc) != strings.ToUpper(c) {
+		t.Errorf("SetWriteFunc failed. Expected: %s, got: %s", strings.ToUpper(c), string(nc))
+	}
+}
+
+// TestPart_SetContent tests Part.SetContent
+func TestPart_SetContent(t *testing.T) {
+	c := "This is a test with ümläutß"
+	m := NewMsg()
+	m.SetBodyString(TypeTextPlain, c)
+	pl, err := getPartList(m)
+	if err != nil {
+		t.Errorf("failed: %s", err)
+		return
+	}
+	cb, err := pl[0].GetContent()
+	if err != nil {
+		t.Errorf("Part.GetContent failed: %s", err)
+	}
+	pl[0].SetContent(strings.ToUpper(string(cb)))
+	nc, err := pl[0].GetContent()
+	if err != nil {
+		t.Errorf("Part.GetContent failed: %s", err)
+	}
+	if string(nc) != strings.ToUpper(c) {
+		t.Errorf("SetContent failed. Expected: %s, got: %s", strings.ToUpper(c), string(nc))
+	}
+}
+
 // getPartList is a helper function
 func getPartList(m *Msg) ([]*Part, error) {
 	pl := m.GetParts()