diff --git a/msg_test.go b/msg_test.go
index 8d106ed..11c9010 100644
--- a/msg_test.go
+++ b/msg_test.go
@@ -4515,6 +4515,21 @@ func TestMsg_AttachFile(t *testing.T) {
 	t.Run("AttachFile with options", func(t *testing.T) {
 		t.Log("all options have already been tested in file_test.go")
 	})
+	t.Run("AttachFile with fileFromFS fails on copy", func(t *testing.T) {
+		message := NewMsg()
+		if message == nil {
+			t.Fatal("message is nil")
+		}
+		message.AttachFile("testdata/attachment.txt")
+		attachments := message.GetAttachments()
+		if len(attachments) != 1 {
+			t.Fatalf("failed to get attachments, expected 1, got: %d", len(attachments))
+		}
+		_, err := attachments[0].Writer(failReadWriteSeekCloser{})
+		if err == nil {
+			t.Error("writer func expected to fail, but didn't")
+		}
+	})
 }
 
 func TestMsg_AttachReader(t *testing.T) {
@@ -4555,6 +4570,32 @@ func TestMsg_AttachReader(t *testing.T) {
 			t.Errorf("expected message body to be %s, got: %s", "This is a test attachment", got)
 		}
 	})
+	t.Run("AttachReader with fileFromReader fails on copy", func(t *testing.T) {
+		message := NewMsg()
+		if message == nil {
+			t.Fatal("message is nil")
+		}
+		file, err := os.Open("testdata/attachment.txt")
+		if err != nil {
+			t.Fatalf("failed to open file: %s", err)
+		}
+		t.Cleanup(func() {
+			if err := file.Close(); err != nil {
+				t.Errorf("failed to close file: %s", err)
+			}
+		})
+		if err = message.AttachReader("attachment.txt", file); err != nil {
+			t.Fatalf("failed to attach reader: %s", err)
+		}
+		attachments := message.GetAttachments()
+		if len(attachments) != 1 {
+			t.Fatalf("failed to get attachments, expected 1, got: %d", len(attachments))
+		}
+		_, err = attachments[0].Writer(failReadWriteSeekCloser{})
+		if err == nil {
+			t.Error("writer func expected to fail, but didn't")
+		}
+	})
 }
 
 func TestMsg_AttachReadSeeker(t *testing.T) {
@@ -4593,6 +4634,30 @@ func TestMsg_AttachReadSeeker(t *testing.T) {
 			t.Errorf("expected message body to be %s, got: %s", "This is a test attachment", got)
 		}
 	})
+	t.Run("AttachReadSeeker with fileFromReadSeeker fails on copy", func(t *testing.T) {
+		message := NewMsg()
+		if message == nil {
+			t.Fatal("message is nil")
+		}
+		file, err := os.Open("testdata/attachment.txt")
+		if err != nil {
+			t.Fatalf("failed to open file: %s", err)
+		}
+		t.Cleanup(func() {
+			if err := file.Close(); err != nil {
+				t.Errorf("failed to close file: %s", err)
+			}
+		})
+		message.AttachReadSeeker("attachment.txt", file)
+		attachments := message.GetAttachments()
+		if len(attachments) != 1 {
+			t.Fatalf("failed to get attachments, expected 1, got: %d", len(attachments))
+		}
+		_, err = attachments[0].Writer(failReadWriteSeekCloser{})
+		if err == nil {
+			t.Error("writer func expected to fail, but didn't")
+		}
+	})
 }
 
 func TestMsg_AttachHTMLTemplate(t *testing.T) {
@@ -4827,6 +4892,21 @@ func TestMsg_EmbedFile(t *testing.T) {
 			t.Fatalf("failed to retrieve attachments list")
 		}
 	})
+	t.Run("EmbedFile with fileFromFS fails on copy", func(t *testing.T) {
+		message := NewMsg()
+		if message == nil {
+			t.Fatal("message is nil")
+		}
+		message.EmbedFile("testdata/embed.txt")
+		emebeds := message.GetEmbeds()
+		if len(emebeds) != 1 {
+			t.Fatalf("failed to get emebeds, expected 1, got: %d", len(emebeds))
+		}
+		_, err := emebeds[0].Writer(failReadWriteSeekCloser{})
+		if err == nil {
+			t.Error("writer func expected to fail, but didn't")
+		}
+	})
 	t.Run("EmbedFile with options", func(t *testing.T) {
 		t.Log("all options have already been tested in file_test.go")
 	})
@@ -4870,6 +4950,53 @@ func TestMsg_EmbedReader(t *testing.T) {
 			t.Errorf("expected message body to be %s, got: %s", "This is a test embed", got)
 		}
 	})
+	t.Run("EmbedReader with fileFromReader fails on copy", func(t *testing.T) {
+		message := NewMsg()
+		if message == nil {
+			t.Fatal("message is nil")
+		}
+		file, err := os.Open("testdata/embed.txt")
+		if err != nil {
+			t.Fatalf("failed to open file: %s", err)
+		}
+		t.Cleanup(func() {
+			if err := file.Close(); err != nil {
+				t.Errorf("failed to close file: %s", err)
+			}
+		})
+		if err = message.EmbedReader("embed.txt", file); err != nil {
+			t.Fatalf("failed to embed reader: %s", err)
+		}
+		embeds := message.GetEmbeds()
+		if len(embeds) != 1 {
+			t.Fatalf("failed to get embeds, expected 1, got: %d", len(embeds))
+		}
+		_, err = embeds[0].Writer(failReadWriteSeekCloser{})
+		if err == nil {
+			t.Error("writer func expected to fail, but didn't")
+		}
+	})
+	t.Run("EmbedReader with fileFromReader on closed reader", func(t *testing.T) {
+		tempfile, err := os.CreateTemp("", "embedfile-close-reader.*.txt")
+		if err != nil {
+			t.Fatalf("failed to create temp file: %s", err)
+		}
+		if err = tempfile.Close(); err != nil {
+			t.Fatalf("failed to close temp file: %s", err)
+		}
+		t.Cleanup(func() {
+			if err := os.Remove(tempfile.Name()); err != nil {
+				t.Errorf("failed to remove temp file: %s", err)
+			}
+		})
+		message := NewMsg()
+		if message == nil {
+			t.Fatal("message is nil")
+		}
+		if err = message.EmbedReader("embed.txt", tempfile); err == nil {
+			t.Fatalf("expected error, got nil")
+		}
+	})
 }
 
 func TestMsg_EmbedReadSeeker(t *testing.T) {
@@ -4908,6 +5035,30 @@ func TestMsg_EmbedReadSeeker(t *testing.T) {
 			t.Errorf("expected message body to be %s, got: %s", "This is a test embed", got)
 		}
 	})
+	t.Run("EmbedReadSeeker with fileFromReadSeeker fails on copy", func(t *testing.T) {
+		message := NewMsg()
+		if message == nil {
+			t.Fatal("message is nil")
+		}
+		file, err := os.Open("testdata/embed.txt")
+		if err != nil {
+			t.Fatalf("failed to open file: %s", err)
+		}
+		t.Cleanup(func() {
+			if err := file.Close(); err != nil {
+				t.Errorf("failed to close file: %s", err)
+			}
+		})
+		message.EmbedReadSeeker("embed.txt", file)
+		embeds := message.GetEmbeds()
+		if len(embeds) != 1 {
+			t.Fatalf("failed to get embeds, expected 1, got: %d", len(embeds))
+		}
+		_, err = embeds[0].Writer(failReadWriteSeekCloser{})
+		if err == nil {
+			t.Error("writer func expected to fail, but didn't")
+		}
+	})
 }
 
 func TestMsg_EmbedHTMLTemplate(t *testing.T) {
diff --git a/msg_unix_test.go b/msg_unix_test.go
index eec15ff..2f5e2d6 100644
--- a/msg_unix_test.go
+++ b/msg_unix_test.go
@@ -22,7 +22,7 @@ func TestMsg_AttachFile_unixOnly(t *testing.T) {
 			t.Skipf("PERFORM_UNIX_OPEN_WRITE_TESTS variable is not set. Skipping unix open/write tests")
 		}
 
-		tempFile, err := os.CreateTemp("testdata/tmp", "attachfile-open-write-test.*.txt")
+		tempFile, err := os.CreateTemp("", "attachfile-open-write-test.*.txt")
 		if err != nil {
 			t.Fatalf("failed to create temp file: %s", err)
 		}
@@ -53,128 +53,6 @@ func TestMsg_AttachFile_unixOnly(t *testing.T) {
 			t.Errorf("expected error to be %s, got: %s", os.ErrPermission, err)
 		}
 	})
-	t.Run("AttachFile with fileFromFS fails on copy", func(t *testing.T) {
-		tempfile, err := os.CreateTemp("testdata/tmp", "attachfile-close-early.*.txt")
-		if err != nil {
-			t.Fatalf("failed to create temp file: %s", err)
-		}
-		t.Cleanup(func() {
-			if err := os.Remove(tempfile.Name()); err != nil {
-				t.Errorf("failed to remove temp file: %s", err)
-			}
-		})
-		message := NewMsg()
-		if message == nil {
-			t.Fatal("message is nil")
-		}
-		message.AttachFile("testdata/attachment.txt")
-		attachments := message.GetAttachments()
-		if len(attachments) != 1 {
-			t.Fatalf("failed to get attachments, expected 1, got: %d", len(attachments))
-		}
-		messageBuf, err := os.Open(tempfile.Name())
-		if err != nil {
-			t.Fatalf("failed to open temp file: %s", err)
-		}
-		// We close early to cause an error during io.Copy
-		if err = messageBuf.Close(); err != nil {
-			t.Fatalf("failed to close temp file: %s", err)
-		}
-		_, err = attachments[0].Writer(messageBuf)
-		if err == nil {
-			t.Error("writer func expected to fail, but didn't")
-		}
-	})
-}
-
-func TestMsg_AttachReader_unixOnly(t *testing.T) {
-	t.Run("AttachReader with fileFromReader fails on copy", func(t *testing.T) {
-		tempfile, err := os.CreateTemp("", "attachfile-close-early.*.txt")
-		if err != nil {
-			t.Fatalf("failed to create temp file: %s", err)
-		}
-		t.Cleanup(func() {
-			if err := os.Remove(tempfile.Name()); err != nil {
-				t.Errorf("failed to remove temp file: %s", err)
-			}
-		})
-		message := NewMsg()
-		if message == nil {
-			t.Fatal("message is nil")
-		}
-		file, err := os.Open("testdata/attachment.txt")
-		if err != nil {
-			t.Fatalf("failed to open file: %s", err)
-		}
-		t.Cleanup(func() {
-			if err := file.Close(); err != nil {
-				t.Errorf("failed to close file: %s", err)
-			}
-		})
-		if err = message.AttachReader("attachment.txt", file); err != nil {
-			t.Fatalf("failed to attach reader: %s", err)
-		}
-		attachments := message.GetAttachments()
-		if len(attachments) != 1 {
-			t.Fatalf("failed to get attachments, expected 1, got: %d", len(attachments))
-		}
-		messageBuf, err := os.Open(tempfile.Name())
-		if err != nil {
-			t.Fatalf("failed to open temp file: %s", err)
-		}
-		// We close early to cause an error during io.Copy
-		if err = messageBuf.Close(); err != nil {
-			t.Fatalf("failed to close temp file: %s", err)
-		}
-		_, err = attachments[0].Writer(messageBuf)
-		if err == nil {
-			t.Error("writer func expected to fail, but didn't")
-		}
-	})
-}
-
-func TestMsg_AttachReadSeeker_unixOnly(t *testing.T) {
-	t.Run("AttachReadSeeker with fileFromReadSeeker fails on copy", func(t *testing.T) {
-		tempfile, err := os.CreateTemp("", "attachfile-close-early.*.txt")
-		if err != nil {
-			t.Fatalf("failed to create temp file: %s", err)
-		}
-		t.Cleanup(func() {
-			if err := os.Remove(tempfile.Name()); err != nil {
-				t.Errorf("failed to remove temp file: %s", err)
-			}
-		})
-		message := NewMsg()
-		if message == nil {
-			t.Fatal("message is nil")
-		}
-		file, err := os.Open("testdata/attachment.txt")
-		if err != nil {
-			t.Fatalf("failed to open file: %s", err)
-		}
-		t.Cleanup(func() {
-			if err := file.Close(); err != nil {
-				t.Errorf("failed to close file: %s", err)
-			}
-		})
-		message.AttachReadSeeker("attachment.txt", file)
-		attachments := message.GetAttachments()
-		if len(attachments) != 1 {
-			t.Fatalf("failed to get attachments, expected 1, got: %d", len(attachments))
-		}
-		messageBuf, err := os.Open(tempfile.Name())
-		if err != nil {
-			t.Fatalf("failed to open temp file: %s", err)
-		}
-		// We close early to cause an error during io.Copy
-		if err = messageBuf.Close(); err != nil {
-			t.Fatalf("failed to close temp file: %s", err)
-		}
-		_, err = attachments[0].Writer(messageBuf)
-		if err == nil {
-			t.Error("writer func expected to fail, but didn't")
-		}
-	})
 }
 
 func TestMsg_EmbedFile_unixOnly(t *testing.T) {
@@ -183,7 +61,7 @@ func TestMsg_EmbedFile_unixOnly(t *testing.T) {
 			t.Skipf("PERFORM_UNIX_OPEN_WRITE_TESTS variable is not set. Skipping unix open/write tests")
 		}
 
-		tempFile, err := os.CreateTemp("testdata/tmp", "embedfile-open-write-test.*.txt")
+		tempFile, err := os.CreateTemp("", "embedfile-open-write-test.*.txt")
 		if err != nil {
 			t.Fatalf("failed to create temp file: %s", err)
 		}
@@ -214,149 +92,6 @@ func TestMsg_EmbedFile_unixOnly(t *testing.T) {
 			t.Errorf("expected error to be %s, got: %s", os.ErrPermission, err)
 		}
 	})
-	t.Run("EmbedFile with fileFromFS fails on copy", func(t *testing.T) {
-		tempfile, err := os.CreateTemp("testdata/tmp", "embedfile-close-early.*.txt")
-		if err != nil {
-			t.Fatalf("failed to create temp file: %s", err)
-		}
-		t.Cleanup(func() {
-			if err := os.Remove(tempfile.Name()); err != nil {
-				t.Errorf("failed to remove temp file: %s", err)
-			}
-		})
-		message := NewMsg()
-		if message == nil {
-			t.Fatal("message is nil")
-		}
-		message.EmbedFile("testdata/embed.txt")
-		emebeds := message.GetEmbeds()
-		if len(emebeds) != 1 {
-			t.Fatalf("failed to get emebeds, expected 1, got: %d", len(emebeds))
-		}
-		messageBuf, err := os.Open(tempfile.Name())
-		if err != nil {
-			t.Fatalf("failed to open temp file: %s", err)
-		}
-		// We close early to cause an error during io.Copy
-		if err = messageBuf.Close(); err != nil {
-			t.Fatalf("failed to close temp file: %s", err)
-		}
-		_, err = emebeds[0].Writer(messageBuf)
-		if err == nil {
-			t.Error("writer func expected to fail, but didn't")
-		}
-	})
-}
-
-func TestMsg_EmbedReader_unixOnly(t *testing.T) {
-	t.Run("EmbedReader with fileFromReader fails on copy", func(t *testing.T) {
-		tempfile, err := os.CreateTemp("", "embedfile-close-early.*.txt")
-		if err != nil {
-			t.Fatalf("failed to create temp file: %s", err)
-		}
-		t.Cleanup(func() {
-			if err := os.Remove(tempfile.Name()); err != nil {
-				t.Errorf("failed to remove temp file: %s", err)
-			}
-		})
-		message := NewMsg()
-		if message == nil {
-			t.Fatal("message is nil")
-		}
-		file, err := os.Open("testdata/embed.txt")
-		if err != nil {
-			t.Fatalf("failed to open file: %s", err)
-		}
-		t.Cleanup(func() {
-			if err := file.Close(); err != nil {
-				t.Errorf("failed to close file: %s", err)
-			}
-		})
-		if err = message.EmbedReader("embed.txt", file); err != nil {
-			t.Fatalf("failed to embed reader: %s", err)
-		}
-		embeds := message.GetEmbeds()
-		if len(embeds) != 1 {
-			t.Fatalf("failed to get embeds, expected 1, got: %d", len(embeds))
-		}
-		messageBuf, err := os.Open(tempfile.Name())
-		if err != nil {
-			t.Fatalf("failed to open temp file: %s", err)
-		}
-		// We close early to cause an error during io.Copy
-		if err = messageBuf.Close(); err != nil {
-			t.Fatalf("failed to close temp file: %s", err)
-		}
-		_, err = embeds[0].Writer(messageBuf)
-		if err == nil {
-			t.Error("writer func expected to fail, but didn't")
-		}
-	})
-	t.Run("EmbedReader with fileFromReader on closed reader", func(t *testing.T) {
-		tempfile, err := os.CreateTemp("", "embedfile-close-early.*.txt")
-		if err != nil {
-			t.Fatalf("failed to create temp file: %s", err)
-		}
-		if err = tempfile.Close(); err != nil {
-			t.Fatalf("failed to close temp file: %s", err)
-		}
-		t.Cleanup(func() {
-			if err := os.Remove(tempfile.Name()); err != nil {
-				t.Errorf("failed to remove temp file: %s", err)
-			}
-		})
-		message := NewMsg()
-		if message == nil {
-			t.Fatal("message is nil")
-		}
-		if err = message.EmbedReader("embed.txt", tempfile); err == nil {
-			t.Fatalf("expected error, got nil")
-		}
-	})
-}
-
-func TestMsg_EmbedReadSeeker_unixOnly(t *testing.T) {
-	t.Run("EmbedReadSeeker with fileFromReadSeeker fails on copy", func(t *testing.T) {
-		tempfile, err := os.CreateTemp("", "embedfile-close-early.*.txt")
-		if err != nil {
-			t.Fatalf("failed to create temp file: %s", err)
-		}
-		t.Cleanup(func() {
-			if err := os.Remove(tempfile.Name()); err != nil {
-				t.Errorf("failed to remove temp file: %s", err)
-			}
-		})
-		message := NewMsg()
-		if message == nil {
-			t.Fatal("message is nil")
-		}
-		file, err := os.Open("testdata/embed.txt")
-		if err != nil {
-			t.Fatalf("failed to open file: %s", err)
-		}
-		t.Cleanup(func() {
-			if err := file.Close(); err != nil {
-				t.Errorf("failed to close file: %s", err)
-			}
-		})
-		message.EmbedReadSeeker("embed.txt", file)
-		embeds := message.GetEmbeds()
-		if len(embeds) != 1 {
-			t.Fatalf("failed to get embeds, expected 1, got: %d", len(embeds))
-		}
-		messageBuf, err := os.Open(tempfile.Name())
-		if err != nil {
-			t.Fatalf("failed to open temp file: %s", err)
-		}
-		// We close early to cause an error during io.Copy
-		if err = messageBuf.Close(); err != nil {
-			t.Fatalf("failed to close temp file: %s", err)
-		}
-		_, err = embeds[0].Writer(messageBuf)
-		if err == nil {
-			t.Error("writer func expected to fail, but didn't")
-		}
-	})
 }
 
 // TestMsg_WriteToSendmailWithContext tests the WriteToSendmailWithContext() method of the Msg