Question

i recently stumbled upon a seemingly weird behavior that Google completely failed to explain.

 using Microsoft.VisualStudio.TestTools.UnitTesting;  class TestClass {     public override bool Equals(object obj)     {         return true;     } }  [TestMethod] public void TestMethod1() {     TestClass t = new TestClass ();     Assert.AreEqual (t, null); // fails     Assert.IsTrue (t.Equals (null)); // passes } 

I would expect this test to succeed. However, in Visual Studio 2008 / .NET 3.5 it fails. Is it intended to be like that or is it a bug?

Answer 1

Your TestClass violates the contract of Object.Equals. Assert.AreEqual is relying on that contract, quite reasonably.

The docs state (in the list of requirements):

• x.Equals(a null reference (Nothing in Visual Basic)) returns false.