Mark assertion functions as helpers

This way test traces will point to the testing code where the assertion
failed. Previously it was always showing the line in the assertion
helpers which was not very helpful.

Author: ironsmile

src/assert/assertfakes/fake_testing_errf.go

@@ -10,6 +10,7 @@ import "fmt"
 // testing.T, testing.TB and similar.
 type TestingErrf interface {
 	Errorf(format string, args ...any)
+	Helper()
 }
 
 func fromMsgAndArgs(msgAndArgs ...any) string {
@@ -22,5 +23,5 @@ func fromMsgAndArgs(msgAndArgs ...any) string {
 		panic("The first argument in msgAndArgs must be a string format value.")
 	}
 
-	return fmt.Sprintf("\n("+fmtStr+")", msgAndArgs[1:]...)
+	return fmt.Sprintf(" ("+fmtStr+")", msgAndArgs[1:]...)
 }

src/assert/common.go

@@ -3,6 +3,8 @@ package assert
 // Equal checks whether expected and actual are actually equal and fails the test
 // if they are not.
 func Equal[V comparable](t TestingErrf, expected, actual V, msgAndArgs ...any) {
+	t.Helper()
+
 	if expected == actual {
 		return
 	}

src/assert/equal.go

@@ -17,6 +17,9 @@ func TestEqual(t *testing.T) {
 	if fakeT.ErrorfCallCount() != 0 {
 		t.Errorf("expected Errorf not to be called for int64 and const expression")
 	}
+	if fakeT.HelperCallCount() != 1 {
+		t.Errorf("expected Helper() to be called on the testing type")
+	}
 
 	assert.Equal(fakeT, 10, actual)
 	if fakeT.ErrorfCallCount() != 1 {

src/assert/equal_test.go

@@ -357,6 +357,8 @@ func TestSearch(t *testing.T) {
 // assertTrack checks that expected is the same as actual but skips
 // checking for the actual track ID as it may not be known beforehand.
 func assertTrack(t *testing.T, expected, actual TrackInfo) {
+	t.Helper()
+
 	if actual.Artist != expected.Artist {
 		t.Errorf("Expected Artist `%s` but found `%s`",
 			expected.Artist, actual.Artist)
@@ -394,6 +396,8 @@ func assertTrack(t *testing.T, expected, actual TrackInfo) {
 
 // assertAlbum asserts that `actual` is the same as `expected`.
 func assertAlbum(t *testing.T, expected, actual Album) {
+	t.Helper()
+
 	assert.Equal(t, expected.Name, actual.Name, "album name")
 	assert.Equal(t, expected.ID, actual.ID, "album ID")
 	assert.Equal(t, expected.Artist, actual.Artist, "album artist")
@@ -408,6 +412,8 @@ func assertAlbum(t *testing.T, expected, actual Album) {
 
 // assertArtist asserts that `actual` is the same as `expected`.
 func assertArtist(t *testing.T, expected, actual Artist) {
+	t.Helper()
+
 	assert.Equal(t, expected.Name, actual.Name, "artist name")
 	assert.Equal(t, expected.ID, actual.ID, "artist ID")
 	assert.Equal(t, expected.AlbumCount, actual.AlbumCount, "albums count")