Asserting for equality anonymous types

Question

I faced a problem asserting two anonymous types.

What I've done so far

I have unit test project which sees the internals of my project under test, so anonymous types are visible to test project.
I've read about anonymous types behaving more like structures(value types) rather than reference types here: Why anonymous types Equals implementation compares fields?

Yet again, while trying to test again equality following assertion exceptions occur:

1.

Assert.IsTrue(actionResult.Value.Equals(expectedActionResult.Value));

Expected: True But was: False

2.

Assert.AreEqual(actionResult.Value, expectedActionResult.Value);

Expected: <{ errorCode = -4, errorMessage = Invalid or Missing parameters within the request. }> (<>f__AnonymousType0'2[System.Int32,System.String]) But was: <{ errorCode = -4, errorMessage = Invalid or Missing parameters within the request. }> (<>f__AnonymousType0'2[System.Int32,System.String])

This is where I create real and expected result:

var actionResult = _systemUnderTest.GetToken(null) as JsonResult;
var expectedActionResult = 
    new JsonResult(new
    {
        errorCode = (int)ErrorCodes.InvalidOrMissingParameters, errorMessage = ErrorCodes.InvalidOrMissingParameters.GetDescription()
    });

What am I missing?

You could also take a look at the answer provided here https://stackoverflow.com/questions/38439811/how-do-you-unit-test-asp-net-core-mvc-controllers-that-return-anonymous-objects/38446754#38446754 — Nkosi, Aug 07 '17 at 10:28

score 2 · Accepted Answer · answered Aug 07 '17 at 08:32

2

Even though the anonymous types are accessible in your test project, that doesn't mean they'll be used when you write new { ... }.

If you look at actionResult.Value.GetType() and expectedActionResult.Value.GetType() I strongly suspect you'll see that they're different types from different assemblies.

The simplest workaround in this case is probably just to compare the resulting JSON instead.

answered Aug 07 '17 at 08:32

Jon Skeet

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`actionResult.Value.GetType().Module.ScopeName` and `expectedActionResult.Value.GetType().ScopeName` yielded their different assemblies, but apart from that at first glance everything else was the same, even the `UnderlyingSystemType` which is strange doesn't compiler generate these names every time and does that mean that anonymous types can't be tested across assemblies? – kuskmen Aug 07 '17 at 08:44
1

@kuskmen: If they're in different assemblies, everything else is completely irrelevant - they're different types. The equality comparison in anonymous types first checks that the types are the same, as is common for equality checks. – Jon Skeet Aug 07 '17 at 08:46
From what I've saw while debugging generated code by the compiler I noticed that casting from object to that particular compiler generated anonymous type fails therefore Equals method returns false. `[DebuggerHidden] public override bool Equals(object value) { var <>f__AnonymousType = value as <>f__AnonymousType0<j__TPar>; return <>f__AnonymousType != null && EqualityComparer<j__TPar>.Default.Equals(this.i__Field, <>f__AnonymousType.i__Field); }` – kuskmen Aug 07 '17 at 09:11

Asserting for equality anonymous types

What I've done so far

1 Answers1