rlen := rand.Intn(len(testString))
		fub := make([]byte, rlen)
		n, _ := buf.Read(fub)
		s = s[n:]
	}
	empty(t, "TestMixedReadsAndWrites (2)", &buf, s, make([]byte, buf.Len()))
}

func TestCapWithPreallocatedSlice(t *testing.T) {
	buf := NewBuffer(make([]byte, 10))
	n := buf.Cap()
	if n != 10 {
		t.Errorf("expected 10, got %d", n)
	}
}

func TestCapWithSliceAndWrittenData(t *testing.T) {