return 0, errors.New("writerWithReadFromError error")
}

func (w writerWithReadFromError) Write(b []byte) (n int, err error) {
	return 10, nil
}

func TestWriterReadFromMustSetUnderlyingError(t *testing.T) {
	var wr = NewWriter(writerWithReadFromError{})
	if _, err := wr.ReadFrom(strings.NewReader("test2")); err == nil {
		t.Fatal("expected ReadFrom returns error, got nil")
	}