XUnit

XUnit is an iteration on NUnit.

By default XUnit runs tests in parallel.

There is a convention to name the object you are testing with a private readonly property called _sut which stands for system under test.

private readonly MyClass _sut;

XUnit creates a new instance of the test class for each test that is run therefore, you can place set up for the tests inside the class body or constructor.

public class MyTestClass
{
  // class body set up here, such as mocks or other dependencies
  private readonly _myObject = new MyObject();

  public MyTestClass()
  {
    // constructor set up here
  }

  // ... individual tests ...
}

Test Categories

There are two major types of test in XUnit: Fact and Theory tests.

Fact tests are invariant and always true, they do not support dynamic inputs.

Theory tests are true for a particular set of data passed into them.

Fact Tests

You can create a new synchronous unit test by creating a new void method and decorating it with the [Fact] attribute.

[Fact]
public void MyTest_TestingFramework_Passes()
{
  Assert.True(true);
}

You can skip a test by adding Skip as an argument to the [Fact] attribute and setting it equal to a string detailing why the test is skipped.

[Fact(Skip = "Redundant Test")]
public void MyTest_TestingFramework_Passes()
{
  Assert.True(true);
}

Theory Tests

You can create a test with multiple test contexts by marking the test with the [Theory] attribute. Data is then passed in using the [InlineData] attribute which takes parameters to the test method as arguments. In the example below the test will pass during its first run and then fail during its second run because the value of input will first be set to 0 from the first InlineData and then to 1 from the second InlineData.

[Theory]
[InlineData(0)]
[InlineData(1)]
public void MyTheory(int input)
{
  Assert.Equal(0, input);
}

You can test data sets with multiple pieces of data by comma separating arguments to InlineData and defining arguments to the test method in the same order.

[Theory]
[InlineData(0, true, "hello")]
public void MyTheory(int n, bool b, string s)
{
  // use n, b and s in your test
}

Assert

You can assert that something is true by using the True method.

Assert.True(true);

You can assert that two things are equal with the Equal method, the arguments are passed in the order of expected and then actual.

Assert.Equal(1, 1);

You can assert against an object’s type by using the BeOfType method in combination with the typeof keyword.

var myString = "Watermelon";
myString.Should().BeOfType(typeof(string));