html/writer_test.go

package html_test

import (
	"errors"
	"io"
)

type errorWriter struct {
	out       io.Writer
	failAfter int
}

func (ew *errorWriter) Write(p []byte) (int, error) {
	wp := p
	if len(wp) > ew.failAfter {
		wp = wp[:ew.failAfter]
	}

	ew.failAfter -= len(wp)
	if ew.out != nil {
		if n, err := ew.out.Write(wp); err != nil {
			return n, err
		}
	}

	if ew.failAfter > 0 {
		return len(wp), nil
	}

	return len(wp), errors.New("test write error")
}