Fluent Assertions

I will explain one of the patterns that I usually use when writing unit tests. Apart from the MOQ library, I use Fluent Assertions(http://www.fluentassertions.com). You can search for that in the Nuget Package Manager and install it in the test project. Out-of-the box, Fluent Assertions provides tons of extension methods that help to easily write assertions on the actual as shown below. In the following example, I will run the test against one sample string of my name.

Now, when I will complete this test, it will be as in the following:

 

[TestMethod]
public void CheckStringValue()
{
    string actual = "Rahul Sahay";
    actual.Should().StartWith("Ra").And.EndWith("ay");
}

When I run it, it will produce the following result.


Similarly, to verify that a collection contains a specified number of elements and that all elements match a predicate, you can test as shown in the following code snippet.

[TestMethod]
public void CheckCollection()
{
    IEnumerable collection = new[] { 1, 2, 3,4,5 };
    collection.Should().HaveCount(6, "because I thought I put 5 items in the collection");
}

Now, when I run the preceding test, it will fail and this will fail due to a valid reason, but look at the error message returned.



Let me show it against one of the infrastructure code where I use it.

[TestMethod]
public void MovieNameTest()
{
    IEnumerable<Movie> movie;
    var mockMovieRepository = MovieRepository(out movie);

    mockMovieRepository.Setup(obj => obj.GetMovies()).Returns(movie);

    IMovieService movieService = new MovieManager(mockMovieRepository.Object);

    IEnumerable<MovieData> data = movieService.GetDirectorNames();

    data.Should().HaveCount(4, "because we put these many values only");


}

Now it has one dependency on MovieRepository (out movie).

private static Mock<IMovieRepository> MovieRepository(out IEnumerable<Movie> movie)
{
    Mock<IMovieRepository> mockMovieRepository = new Mock<IMovieRepository>();

    //Mock return as GetMovies returns that, so we are not going to hit db
    //we are going to return mocked up entity
    movie = new Movie[]
    {
        new Movie()
        {
            MovieName = "Avatar",
            DirectorName = "James Cameron",
            ReleaseYear = "2009"
        },
        new Movie()
        {
            MovieName = "Titanic",
            DirectorName = "James Cameron",
            ReleaseYear = "1997"
        }
    };
    return mockMovieRepository;
}

When we run the preceding test, it will again throw a similar error because count is 2 and we're checking for 4.



Thanks for joining me. I hope you will like it.