},
		},
		{
			desc:       "Nested hash reader NewReader() should merge.",
			src:        mustReader(t, bytes.NewReader([]byte("abcd")), 4, "", "", 4),
			size:       4,
			actualSize: 4,
		},
		{
			desc:       "Incorrect sha256, nested",
			src:        mustReader(t, bytes.NewReader([]byte("abcd")), 4, "", "", 4),
			size:       4,
			actualSize: 4,

	type nErr struct {
		n   int64
		err error
	}
	type justReader struct {
		io.Reader
	}
	type justWriter struct {
		io.Writer
	}
	discard := justWriter{io.Discard} // hide ReadFrom

	var with, withOut nErr
	with.n, with.err = io.Copy(discard, NewReader(nil))
	withOut.n, withOut.err = io.Copy(discard, justReader{NewReader(nil)})
	if with != withOut {