public void TwoWayDictionary_Add_ShouldAddItemToBothDictionaries()
{
int i = 1;
string s = "one";
_sut.Add(i, s);
_sut._forwardDict[i].Should().Be(s);
_sut._reverseDict[s].Should().Be(i);
_sut[i].Should().Be(s);
_sut.GetByKey(i).Should().Be(s);
_sut.GetByValue(s).Should().Be(i);
}