Unit test syntax for C#

inline-unit-test.cs

public class HelloWorld
{
  public string Say()
  {
    return "Hello World!";
  }

  test
  {
    void Say_ReturnsHelloWorld()
    {
      var hello = new HelloWorld();
      Assert.That(hello.Say(), Is.EqualTo("Hello World!"));
    }
  }  
}