public void StringArgumentExeptionTest(string string1, string string2)
{
TestDelegate action = () => Task4.Concat(string1, string2);
Assert.Throws <ArgumentException>(action);
}
public void ConcatTests(string string1, string string2, string expected)
{
string newString = Task4.Concat(string1, string2);
Assert.That(newString, Is.EqualTo(expected));
}