Comparing xUnit.net to other frameworks

Table of Contents

Attributes

NUnit 3.x MSTest 15.x xUnit.net 2.x Comments
[Test] [TestMethod] [Fact] Marks a test method.
[TestFixture] [TestClass] n/a xUnit.net does not require an attribute for a test class; it looks for all test methods in all public (exported) classes in the assembly.
Assert.That
Record.Exception
[ExpectedException] Assert.Throws
Record.Exception
xUnit.net has done away with the ExpectedException attribute in favor of Assert.Throws. See Note 1
[SetUp] [TestInitialize] Constructor We believe that use of [SetUp] is generally bad. However, you can implement a parameterless constructor as a direct replacement. See Note 2
[TearDown] [TestCleanup] IDisposable.Dispose We believe that use of [TearDown] is generally bad. However, you can implement IDisposable.Dispose as a direct replacement. See Note 2
[OneTimeSetUp] [ClassInitialize] IClassFixture<T> To get per-class fixture setup, implement IClassFixture<T> on your test class. See Note 3
[OneTimeTearDown] [ClassCleanup] IClassFixture<T> To get per-class fixture teardown, implement IClassFixture<T> on your test class. See Note 3
n/a n/a ICollectionFixture<T> To get per-collection fixture setup and teardown, implement ICollectionFixture<T> on your test collection. See Note 3
[Ignore("reason")] [Ignore] [Fact(Skip="reason")] Set the Skip parameter on the [Fact] attribute to temporarily skip a test.
[Property] [TestProperty] [Trait] Set arbitrary metadata on a test
[Theory] [DataSource] [Theory]
[XxxData]
Theory (data-driven test). See Note 4

Attribute Notes

Note 1: Long-term use of [ExpectedException] has uncovered various problems with it. First, it doesn’t specifically say which line of code should throw the exception, which allows subtle and difficult-to-track failures that show up as passing tests. Second, it doesn’t offer the opportunity to fully inspect details of the exception itself, since the handling is outside the normal code flow of the test. Assert.Throws allows you to test a specific set of code for throwing an exception, and returns the exception during success so you can write further asserts against the exception instance itself.

Note 2: The xUnit.net team feels that per-test setup and teardown creates difficult-to-follow and debug testing code, often causing unnecessary code to run before every single test is run. For more information, see http://jamesnewkirk.typepad.com/posts/2007/09/why-you-should-.html.

Note 3: xUnit.net provides a new way to think about per-fixture data with the use of the IClassFixture<T> and ICollectionFixture<T> interfaces. The runner will create a single instance of the fixture data and pass it through to your constructor before running each test. All the tests share the same instance of fixture data. After all the tests have run, the runner will dispose of the fixture data, if it implements IDisposable. For more information, see Shared Context.

Note 4: xUnit.net ships with support for data-driven tests call Theories. Mark your test with the [Theory] attribute (instead of [Fact]), then decorate it with one or more [XxxData] attributes, including [InlineData] and [MemberData]. For more information, see Getting Started.

Assertions

NUnit uses a Constraint Model. All the assertions start with Assert.That followed by a constraint. In the table below, we compare NUnit constraints, MSTest asserts, and xUnit asserts.

NUnit 3.x (Constraint) MSTest 15.x xUnit.net 2.x Comments
Is.EqualTo AreEqual Equal MSTest and xUnit.net support generic versions of this method
Is.Not.EqualTo AreNotEqual NotEqual MSTest and xUnit.net support generic versions of this method
Is.Not.SameAs AreNotSame NotSame  
Is.SameAs AreSame Same  
Does.Contain Contains Contains  
Does.Not.Contain DoesNotContain DoesNotContain  
Throws.Nothing n/a DoesNotThrow Ensures that the code does not throw any exceptions
n/a Fail n/a xUnit.net alternative: Assert.True(false, "message")
Is.GreaterThan n/a n/a xUnit.net alternative: Assert.True(x > y)
Is.InRange n/a InRange Ensures that a value is in a given inclusive range
Is.AssignableFrom n/a IsAssignableFrom  
Is.Empty n/a Empty  
Is.False IsFalse False  
Is.InstanceOf<T> IsInstanceOfType IsType<T>  
Is.NaN n/a n/a xUnit.net alternative: Assert.True(double.IsNaN(x))
Is.Not.AssignableFrom<T> n/a n/a xUnit.net alternative: Assert.False(obj is Type)
Is.Not.Empty n/a NotEmpty  
Is.Not.InstanceOf<T> IsNotInstanceOfType IsNotType<T>  
Is.Not.Null IsNotNull NotNull  
Is.Null IsNull Null  
Is.True IsTrue True  
Is.LessThan n/a n/a xUnit.net alternative: Assert.True(x < y)
Is.Not.InRange n/a NotInRange Ensures that a value is not in a given inclusive range
Throws.TypeOf<T> n/a Throws<T> Ensures that the code throws an exact exception

Sources

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