✅ Add test for WaitForError when firstErr is already set

waiterr_test.go

@@ -103,3 +103,23 @@ func TestWaitForErrorPanic(t *testing.T) {
 	we := new(waiterr.WaitErr)
 	_ = we.WaitForError()
 }
+
+func TestWaitForErrorFirstErrSet(t *testing.T) {
+	we := new(waiterr.WaitErr)
+	expectedErr := errors.New("pre-set error")
+
+	// Manually set firstErr (requires reflection or a way to access unexported fields)
+	// For testing purposes, we can simulate this by calling Go with an error first
+	we.Go(func() error { return expectedErr })
+	we.Go(func() error { return errors.New("another error") })
+	we.Go(func() error { return nil })
+
+	// Wait for a short period to ensure the first error is processed
+	// In a real scenario, this might be handled by a channel or more robust synchronization
+	// For this test, we'll rely on the Go routine scheduling to set firstErr quickly
+	_ = we.WaitForError() // Call once to ensure firstErr is set internally
+
+	// Now call WaitForError again, expecting it to return the already set firstErr
+	actualErr := we.WaitForError()
+	be.Err(t, actualErr, expectedErr)
+}