Add tests for substituted properties that used as argument matchers

[alexandrnikitin]

Adds tests for substituted properties used as argument matchers.

[alexandrnikitin]

Following questions, should these tests fail:

        [Test]
        public void Return_result_for_property_argument()
        {
            _something.SomeProperty = 2;
            Arg.Any<int>()
            _something.Echo(_something.SomeProperty);

            Assert.That(_something.Echo(1), Is.EqualTo(""), "First return");
            Assert.That(_something.Echo(2), Is.EqualTo("two"), "Second return");
        }

        [Test]
        public void Return_result_for_property_argument()
        {
            _something.SomeProperty = 2;
            Arg.Any<int>()
            // same but with Returns
            _something.Echo(_something.SomeProperty).Returns("two");

            Assert.That(_something.Echo(1), Is.EqualTo(""), "First return");
            Assert.That(_something.Echo(2), Is.EqualTo("two"), "Second return");
        }

[zvirja]

Well, Returns() shouldn't matter, as fail is expected to happen during the call dispatch.

I'd say that both the scenarios should fail on the _something.Echo(...) line.

[alexandrnikitin]

Yes, I would expect that. But now it fails for _something.Echo(...) see https://travis-ci.org/nsubstitute/NSubstitute/jobs/349729578#L793 but works for _something.Echo(...).Returns()

[zvirja]

Ok, probably we should align, because I see a bit different results.
Both the scenarios provided here work fine for me. For both the tests I see that they fail due to redundant specifier - expected behavior.

Now about the reason of the CI failure. The following test failed:

        [Test]
        public void Should_fail_with_redundant_exception_if_more_specifications_than_arguments_scenario_4()
        {
            // This spec will be ignored, however it's good to let user know that test might not work how he expects.
            Arg.Is(42);

            var ex = Assert.Throws<RedundantArgumentMatcherException>(() =>
            {
                _something.Echo(_something.SomeProperty);
            });
            Assert.That(ex.Message, Contains.Substring("42"));
        }

The scenario is a bit tricky. If you add _something.SomeProperty = 2; before Arg.Is(42), the test will pass (i.e. the expected exception will be thrown). The reason why it fails in the current shape is following:

1. Arg.Is(42) - specifier is pushed to stack.
2. _something.SomeProperty - property getter is called. Method doesn't have arguments, so queued spec remains. Property returns 0, as value is not configured and the default one is returned.
3. _something.Echo(..) is invoked with 0 as a parameter value. It consumes the queued Arg.Is(42) and mistakenly match that specifier with the first parameter value.

From NSubstitute perspective there is no way to handle this scenario (currently). Probably, we could find those ways, but it's a matter of a separate discussion.

I'd suggest to transform this test and add _something.SomeProperty = 2; before Arg.Is(42). In this case it will have a chance to fail and the newly added feature will shine 😉

[alexandrnikitin]

@zvirja You are right! Thanks. I fixed the test to reflect the supported case.

[zvirja]

@alexandrnikitin LGTM ☺️

[dtchepak]

Thanks everyone 😄👍