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Bug in 5.3.0 related to generics

0 votes
Hi,

The 5.3.0 release almost got generics right. I've found one bug that is triggered in case expectation is set multiple times on the same method. Here's the code: 

        public static class DataHelper
        {
            public static LT Fill<T>()
                where LT : ICollection<T>, new()
            {
                return new LT();
            }
        }

        [Test]
        public void Test_Succeeds()
        {
            var fakeStrings = new List<string>();
            fakeStrings.Add("abc");

            Isolate.WhenCalled(() => DataHelper.Fill<string, List<string>>()).WillReturn(fakeStrings);

            var strings = DataHelper.Fill<string, List<string>>();
            Assert.IsNotNull(strings);
            Assert.AreNotEqual(0, strings.Count);
        }

        [Test]
        public void Test_Fails()
        {
            var fakeStrings = new List<string>();
            fakeStrings.Add("abc");

            Isolate.WhenCalled(() => DataHelper.Fill<string, List<string>>()).WillReturn(fakeStrings);
            Isolate.WhenCalled(() => DataHelper.Fill<string, List<string>>()).WillReturn(fakeStrings);

            var strings = DataHelper.Fill<string, List<string>>();
            Assert.IsNotNull(strings);
            Assert.AreNotEqual(0, strings.Count);
        }


As you can see, the only difference between the successful and failed test is that DataHelper.Fill is faked twice in failed test. But this breaks the list that it returns: the return value is an empty list instead of a list containing string "abc".
asked by vagif
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 (19.4k points)

8 Answers

0 votes
There are more tests that are now broken. I did not have time to recreate them using simple examples, but they all have common pattern:
- They use generics in method signature;
- There are more than one fakes created on such methods (often using different specialization).

For example, the test with the code fails: 

            var fake = Isolate.Fake.Instance<CpLanguages>();
            Isolate.WhenCalled(() => CpGlobal<CpGlobalProperties>.Languages).WillReturn(fake);
            Isolate.WhenCalled(() => CpGlobal<CpGlobalProperties>.LanguageNames(null)).WillReturn(fake);


But a similar test with only one WhenCalled succeeded. In fact all tests that have multiple WhenCalled applied to methods with generics fail now.
answered by vagif
Report User
 (19.4k points)
0 votes
Hi Vagif,

This should obviously work - we will investigate it and get back to you on this forum.

Doron
Typemock Support
answered by doron
Report User
 (17.2k points)
0 votes
Hi Vagif

I checked the example you gave and it seems like a bug in generic static methods.
The workaround for the moment is to use:
Isolate.Fake.StaticMethods(typeof(DataHelper));
This fixed the example you gave.
Can you please try it in the other tests and see if it works?

Thanks for the report.
answered by ohad
Report User
 (35.4k points)
0 votes
Well done! Your workaround worked for all broken tests. I re-enabled them. Thanks a lot!
answered by vagif
Report User
 (19.4k points)
0 votes
This issue still seems to occur in Typemock 5.3.4, when calling static methods without generics: 

Isolate.WhenCalled(()=>Config.GetSetting("mysetting")).WithExactArguments().WillReturn("hello");


Without any other mocking fails. This, however, works: 

Isolate.Fake.StaticMethods(typeof(Config));
Isolate.WhenCalled(()=>Config.GetSetting("mysetting")).WithExactArguments().WillReturn("hello");
answered by zcrar70
Report User
 (2.9k points)
0 votes
zcrar70,

How does this fail for you? What error message/behavior are you getting?

Can you post the code for the Config class?

Thanks,
Doron
Typemock Support
answered by doron
Report User
 (17.2k points)
0 votes
Hi,

The error I get when omitting 'Isolate.Fake.StaticMethods(typeof(Config))' is just that the underlying method gets called.

I don't really want to post the Config class here, but I don't seem to be able to reproduce it with a test class with similar characteristics; so it definitely semes like something related to that specific class as opposed to static methods in general. I'll have another go and post back here if I get anywhere with reproducing this with a test class.

Thanks,
Nick
answered by zcrar70
Report User
 (2.9k points)
0 votes
Thanks, Nick.

Also, can you try an upgrade to the latest version (5.3.4)? It contains a few improvements around generics handling which may affect this issue.

Doron
Typemock Support
answered by doron
Report User
 (17.2k points)
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