Microsoft Fakes (formerly Moles)

Problem: You are writing unit tests that involve a dependency on a 3rd party concrete class. Unfortunately there are no interfaces, nor are the methods/properties defined as virtual.

Solution: Microsoft Fakes (formerly Moles)

Microsoft Fakes help you isolate the code you are testing by replacing other parts of the application with stubs or shims. These are small pieces of code that are under the control of your tests. By isolating your code for testing, you know that if the test fails, the cause is there and not somewhere else. Stubs and shims also let you test your code even if other parts of your application are not working yet.


[code lang=”csharp”]

// Code under test:
public int GetTheCurrentYear()
return DateTime.Now.Year;

[TestClass] public class TestClass1
[TestMethod] public void TestCurrentYear()
int fixedYear = 2000;

// Shims can be used only in a ShimsContext:
using (ShimsContext.Create())
// Arrange:
// Shim DateTime.Now to return a fixed date:
System.Fakes.ShimDateTime.NowGet =
() =>
{ return new DateTime(fixedYear, 1, 1); };

// Instantiate the component under test:
var componentUnderTest = new MyComponent();

// Act:
int year = componentUnderTest.GetTheCurrentYear();

// Assert:
// This will always be true if the component is working:
Assert.AreEqual(fixedYear, year);

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