w.readFromBytes += len(b)
	return int64(len(b)), err
}

// Test that calling (*Writer).ReadFrom with a partially-filled buffer
// fills the buffer before switching over to ReadFrom.
func TestWriterReadFromWithBufferedData(t *testing.T) {
	const bufsize = 16

	input := createTestInput(64)
	rfw := &readFromWriter{}
	w := NewWriterSize(rfw, bufsize)

	const writeSize = 8