In this article, I’m sharing how this can be done ? It will also be useful if you use another testing framework than NUnit, but the examples are based on it.

Starting point

You can find the code accompanying this article here: https://github.com/dsibinski/cypress-csharp-example

Our starting point is a React application with Cypress tests:

I assume that your tests specs are placed within cypress/integration folder. The only spec we have is called submit_spec.ts and it placed in a subfolder called form.

Now imagine, that your backend is written in C#. Maybe you’d like to perform some data initialization before Cypress tests are executed.

In our case, we have a C# backend, and we’ve already had a mechanism for running integration tests. This mechanism runs our server app with an in-memory database, which makes the maintenance of tests very easy.

We wanted to use the same mechanism for our new, E2E Cypress tests. It means that we would be able to write some C# initialization code (data creation mostly) and then run Cypress tests from NUnit test.

What we want to achieve is to have a C#-Cypress NUnit test look as follows:

Let’s now see how we can implement the RunCypressTest method ?

Implementing a method to run Cypress tests from NUnit

To make things easier, let’s create a base class all our test classes can use. We’ll call it CypressTestsBase and add a RunCypressTest method to it:

This code does the job. Few interesting parts:

• Line 12 – I’m getting there the path to the web app workspace where npx cypress run command can be executed. It might be more complicated in your scenario, so you should adjust accordingly here
• Lines 13-20: thanks to setting RedirectStandardInput to true, we can later execute a custom command via cmd; setting RedirectStandardOutput to true allows us to write everything npx cypress run command does to NUnit test’s output
• Line 28: TestContext.Out.WriteLine(cypressProcessOutput); actually writes the Cypress output to NUnit test result
• Line 29: here we handle errors during Cypress execution. npx cypress run executed via cmd will return a code different from 0 if anything goes wrong.

We can now change FormTests class to run its corresponding Cypress test:

Finally, it allows to run our C# test, which then runs its corresponding Cypress spec and prints the output:

Cypress errors in NUnit result

Let’s see what happens if something is broken on Cypress/web app’s side. Let’s run our test, but with our web app not running.

The NUnit test fails, and we can clearly see what was wrong:

You will see similar errors if something goes wrong in a Cypress test. Cypress also saves compressed videos and screenshots, so if something goes wrong, diagnosing such failed tests is very easy.

Summary

I hope you found this article on how to run Cypress tests from NUnit useful. Remember that it not only works with NUnit – it will be suitable for any testing framework. You might need to adjust some parts of the solution, e.g. printing the results to the test result’s output.

This solution allowed us to improve our testing by adding a new type of tests to our pipeline. Right next to proper naming and mutation testing, E2E tests add another layer of security and improve the quality of our software.

Once more, you can find the complete source code here. If you want, feel free to copy it and change it according to your needs ?

The post Run Cypress Tests From NUnit Test (C#) appeared first on Yumasoft.

We will go through a step-by-step example in building our own custom collection to see how all that works. Let’s dive in! ?

Throughout this article, I’m working with a Unit Tests project using .NET 5, C# 9.0 and NUnit. It makes it easier to play with the code on your own. We can create our custom collection and at the same time try it out in a foreach loop in a test method. I recommend this approach for testing out various programming concepts for yourself ?

Custom collection implementing IEnumerable<T>

First, we want to implement our own, custom collection in C#. The most obvious solution is to implement IEnumerable<T> interface. Our IDE will require our class to implement IEnumerator GetEnumerator() and IEnumerator IEnumerable.GetEnumerator() methods, so let’s do that:

Of course, this is just an example to satisfy the foreach loop, so we won’t care about the actual implementation of these methods ?

Custom collection implemented in such a way can be used in foreach loop:

Does foreach require IEnumerable?

Let’s try to get rid of implementing IEnumerable interface. As soon as we do it, our IDE complains:

Let’s try to remove IEnumerable.GetEnumerator() method completely, so our custom collection looks as follows:

Now guess what – we can still use MyCollection within the foreach loop!

So you already know that, when asked during an interview whether foreach needs a collection to implement IEnumerable, the answer is no ?

Custom IEnumerator

Currently, our collection has a single GetEnumerator() method returning IEnumerator<MyObject>. We already know that this method is needed in a collection to be able to use it within a foreach loop.

However, let’s work on what this method returns. We’ll implement our custom IEnumerator. Again – the most obvious solution is to create a class implementing IEnumerator<T> interface:

That’s the implementation proposed by the IDE (Rider). We can now change our collection to use this custom enumerator. See that it can still be used within foreach:

So far, so good. But why all these methods in MyObjectEnumerator? ?

Does foreach need an enumerator implementing IEnumerator?

If we remove inheritance from IEnumerator from MyObjectEnumerator, the IDE only complains about IEnumerator.Current property, so let’s get rid of it. Our custom enumerator now looks as follows:

Yeah, you guessed it again – we can still use our collection in a foreach loop ?

However… Does our custom enumerator really needs all of these stuff: MoveNext(), Reset(), Dispose() and MyObject Current ? Let’s remove all of them and see what our IDE tells us:

That’s the error from IDE when trying to iterate through our custom collection in foreach:

Type ‘ForeachFun.MyCollection’ cannot be used in ‘foreach’ statement because it neither implements ‘IEnumerable’ or ‘IEnumerable’, nor has suitable ‘GetEnumerator’ method which return type has ‘Current’ property and ‘MoveNext’ method

This error actually tells us everything. This is the ultimate answer to the legendary C# interview question: “What does a collection need to be able to use it in foreach loop?”. In other words: “Is it necessary for a collection to implement IEnumerable to use it in a foreach loop?”

The answer is: a collection needs to have a GetEnumerator() method returning an object of type having Current property and bool MoveNext() method. No interfaces are required anywhere here ?

The compiler uses duck typing to find these two necessary ingredients of the type returned from GetEnumerator(). It means that is looks for these properties by text. Later, depending on the type of Current property, a single element inside the foreach is typed accordingly. Only if this duck searching fails, the compiler checks whether the collection implements the interfaces.

In the end, this is our simplest and fully legit code (except the actual implementations of the methods, which is out of scope of this article):

Summary

I hope you got to know something new about foreach loop from this article. This may not sound like a knowledge you’d need on a daily basis, but it’s worth knowing how stuff works under the hood ? Plus, you can always score a point during your next interview ?!

The post Foreach, IEnumerable and IEnumerator in C# appeared first on Yumasoft.