package websocket

import (
	"bytes"
	"io"
	"testing"
)

type nopCloser struct{ io.Writer }

func (nopCloser) Close() error { return nil }

func TestTruncWriter(t *testing.T) {
	const data = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijlkmnopqrstuvwxyz987654321"
	for n := 1; n <= 10; n++ {
		var b bytes.Buffer
		w := &truncWriter{w: nopCloser{&b}}
		p := []byte(data)
		for len(p) > 0 {
			m := len(p)
			if m > n {
				m = n
			}
			w.Write(p[:m])
			p = p[m:]
		}
		if b.String() != data[:len(data)-len(w.p)] {
			t.Errorf("%d: %q", n, b.String())
		}
	}
}