Key xUnit features

In xUnit, the [Fact] attribute is the way to create unique test cases, while the [Theory] attribute is the way to make data-driven test cases. Let’s start with facts, the simplest way to write a test case.

Facts

Any method with no parameter can become a test method by decorating it with a [Fact] attribute, like this:

public class FactTest
{
    [Fact]
    public void Should_be_equal()
    {
        var expectedValue = 2;
        var actualValue = 2;
        Assert.Equal(expectedValue, actualValue);
    }
}

You can also decorate asynchronous methods with the fact attribute when the code under test needs it:

public class AsyncFactTest
{
    [Fact]
    public async Task Should_be_equal()
    {
        var expectedValue = 2;
        var actualValue = 2;
        await Task.Yield();
        Assert.Equal(expectedValue, actualValue);
    }
}

In the preceding code, the highlighted line conceptually represents an asynchronous operation and does nothing more than allow...