tests := []struct {
		name     string
		r        io.Reader
		bufSize  int // 0 means 16
		peekSize int

		n int // input to Discard

		want    int   // from Discard
		wantErr error // from Discard

		wantBuffered int
	}{
		{
			name:         "normal case",
			r:            strings.NewReader("abcdefghijklmnopqrstuvwxyz"),
			peekSize:     16,
			n:            6,