tasking/t.go
func (t *T) Errorf(format string, args ...interface{}) {
	fmt.Fprintf(os.Stderr, format, args...)
	t.Fail()
}
func (t *T) Errorf(format string, args ...interface{}) {
	fmt.Fprintf(os.Stderr, format, args...)
	t.Fail()
}
func ( t * T ) Errorf ( format string , args ... interface { } ) { fmt . Fprintf ( os . Stderr , format , args ... ) t . Fail ( ) }
// Errorf is equivalent to Logf followed by Fail.
Errorf is equivalent to Logf followed by Fail .