Check support of xunit

[constructor-igor]

If xunit have something as Assert.That, suggested to support it too.

[constructor-igor]

supported 2 xunit use cases:

        [Fact]
        [ExpectedException]
        public void ExpectedExceptionTestV1()
        {
            double r = DivException(2, 0);
        }
        [Fact]
        [ExpectedException(typeof(ArgumentException))]
        public void ExpectedExceptionTestV1_with_type()
        {
            double r = DivArgumentException(2, 0);
        }

to

        [Fact]
        public void ExpectedExceptionTestV1()
        {
            Assert.Throws<Exception>(() => { double r = DivException(2, 0); });
        }

        [Fact]
        public void ExpectedExceptionTestV1_with_type()
        {
            Assert.Throws<ArgumentException>(() => { double r = DivArgumentException(2, 0); });
        }

[constructor-igor]