Is there a more appropriate to test if the constructor throws an exception?

Question

Normally you test, if an exception gets thrown in a certain method, as follows. I use FluentAssertions:

[Fact]
public void Exception_gets_thrown()
{
    // Arrange
    var foo = new Foo("validArgument");

    // Act/Assert
    foo.Invoking(f => f.Bar(null))            // null is an invalid argument
       .ShouldThrow<ArgumentNullException>();
}

But how to test, if an exception gets thrown in the constructor? I just did it like this, but is there maybe a more appropriate way via FluentAssertions?

[Fact]
public void Constructor_throws_Exception()
{
    // Arrange
    Action a = () => new Foo(null);         // null is an invalid argument

    // Act/Assert
    a.ShouldThrow<ArgumentNullException>();
}

Answer 1

That's exactly how you're supposed to test for exceptions and that's what ShouldThrow<T>() and ShouldNotThrow<T>() were designed for in the first place. In fact, the Invoking() approach might be marked as obsolete in the next big version (2.0.0).