written := w.Bytes()
			if len(written) != nwrite {
				t.Errorf("%s: %d bytes written", context, len(written))
			}
			for l := 0; l < len(written); l++ {
				if written[l] != data[l] {
					t.Errorf("wrong bytes written")
					t.Errorf("want=%q", data[0:len(written)])
					t.Errorf("have=%q", written)
				}
			}
		}
	}
}

func TestWriterAppend(t *testing.T) {
	got := new(bytes.Buffer)