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.

produce

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.

error

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

6 Comments

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Guest User11y ago
thanks for sharing, i'll use this nuget package
Pankaj Kumar Choudhary11y ago
Nice Article Sir............
Saroj Kumar Sahu11y ago
Thanks for sharing...
Santhakumar Munuswamy11y ago
Thanks for good show
Ramesh Maruthi11y ago
Good one, similar to mocking test....
Neeraj Kumar11y ago
good