f := l.Function
	if l.Line == 0 || f == nil || f.Name == "" || f.Filename == "" {
		return false
	}
	return true
}

// TestFakeMapping tests if at least one mapping exists
// (including a fake mapping), and their HasFunctions bits
// are set correctly.
func TestFakeMapping(t *testing.T) {
	var buf bytes.Buffer
	if err := Lookup("heap").WriteTo(&buf, 0); err != nil {
		t.Fatalf("failed to write heap profile: %v", err)