public void Test_is_reflexive()
{
var binaryRelation = new Set<Tuple<int, int>> {new Tuple<int, int>(1, 1), new Tuple<int, int>(1, 2)};
binaryRelation.IsReflexive().ShouldBeFalse();
binaryRelation.Add(new Tuple<int, int>(2, 2));
binaryRelation.IsReflexive().ShouldBeTrue();
binaryRelation.IsEquivalenceRelation().ShouldBeFalse();
}