public void RotateArray_Throw_Exception() { //arrange var moqRotateArray = new RotateArray(); var expectedResult = new ArgumentNullException(); //act var sut = Assert.Throws <ArgumentNullException>( () => moqRotateArray.GetRotateArray(null, -1), "should not be null parameters and number should be more than 0"); //act Assert.AreEqual(sut.InnerException, expectedResult.InnerException); }