Remove obsolete tests and add error handling test

Removed commented-out tests to clean up the codebase. Added a new test to verify behavior when the file is closed early during attachment, ensuring robustness.

msg_nowin_test.go

@@ -85,6 +85,55 @@ func TestMsg_AttachFile_unixOnly(t *testing.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")
+		}
+		if !errors.Is(err, os.ErrClosed) {
+			t.Errorf("expected error to be %s, got: %s", os.ErrClosed, err)
+		}
+	})
+}
+
 // TestMsg_WriteToSendmailWithContext tests the WriteToSendmailWithContext() method of the Msg
 func TestMsg_WriteToSendmailWithContext(t *testing.T) {
 	if os.Getenv("TEST_SENDMAIL") != "true" {

msg_test.go

@@ -4533,7 +4533,7 @@ func TestMsg_AttachReader(t *testing.T) {
 				t.Errorf("failed to close file: %s", err)
 			}
 		})
-		if err := message.AttachReader("attachment.txt", file); err != nil {
+		if err = message.AttachReader("attachment.txt", file); err != nil {
 			t.Fatalf("failed to attach reader: %s", err)
 		}
 		attachments := message.GetAttachments()
@@ -4556,23 +4556,6 @@ 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 non-existant file", func(t *testing.T) {
-			message := NewMsg()
-			if message == nil {
-				t.Fatal("message is nil")
-			}
-			message.AttachReader("testdata/non-existant-file.txt")
-			attachments := message.GetAttachments()
-			if len(attachments) != 0 {
-				t.Fatalf("failed to retrieve attachments list")
-			}
-		})
-		t.Run("AttachReader with options", func(t *testing.T) {
-			t.Log("all options have already been tested in file_test.go")
-		})
-
-	*/
 }
 
 /*