If you followed through, you’ll have the main tools for a nice test suite in your NestJS application! 3466. By using a whole other class (the fake), all the logic related to the database module is gone. Run local tests. But the main advantage in NestJS about unit testing is the ability to create your components using Dependency Injection. Each folder is a fully functional Nest application on its own. This setup would be ideal to test things like creating a playlist; we would check whether the repository is called with the expected parameters. Keeping the variables’ names structured like that helped me personally to keep my tests cleaner and more readable overall. By keeping a reference to the spy (assigning it to a variable), we can later on, in the test, do the following: Note that the variable name consists of three parts: first, the name of the object that is being overriden; second, the method’s name; and third, the word Spy, so we can easily distinguish it from our other variables. The testing pyramid has been described with some different shapes, but the main idea remains universal: we should write more of the simpler tests and less of the more complicated ones, without leaving any of them behind. In our example backend, the external service is the student database API. After writing these two test scenarios, the one with the error and the happy path, we can now be sure that, assuming the dependencies work exactly like their contracts (the provided mocks and stubs), the .createOne() method works correctly. That’s because the mock action will happen inside of each test! Simple of unit-testing applications; Made for Monoliths and Micro-administrations (whole segment in the documentation with respect to the Microservice sort of a NestJS application, just as methods and plans). Nest takes testing very seriously and provides testing utilities in order to make the process as smooth as possible. In this snippet, we use .mockResolvedValue() as opposed to .mockReturnValue() due to the original implementation returning a promise. I am really stucked with writing unit test cases with nest.js. That’s great! ... NestJS is a Node.js back-end development framework built upon Express, leveraging the power of TypeScript. An example of a matcher would be the .toEqual() method that checks whether two objects are the same. Description. Do you use other techniques for testing a NestJS app? The KISS (Keep It Simple, Stupid) principle applies to tests as well. We have to write our code in books.controller.ts. The first scenario is done. ... using that awesome plugin, your unit tests are passing, you fire up your e2e tests and everything fails. Using GraphQL with NestJS. It uses progressive JavaScript, is built with and fully supports TypeScript (yet still enables developers to code in pure JavaScript) and combines elements of OOP (Object Oriented Programming), FP (Functional Programming), and FRP (Functional Reactive Programming). As you add new JavaScript libraries and other dependencies to your app, you’ll need more visibility to ensure your users don’t run into unknown issues. Before you start testing I would recommend being familiar with the testing pyramid and other best practices like the KISS (Keep it simple stupid) technique. When doing unit test with @nestjs/testing after creating the module and declare … Next, we’re setting up our test configurations inside beforeAll: We’ll use the TestingModule from the Nest testing package, which takes every provider and module you need for testing. In a more sophisticated setup, we would probably create separate classes for each case (one for creating, one for updating) and their related logic, but we are going to keep it simple. Having a well tested backend is an important step for having a successful product. Let’s quickly take a look at the .createOne() method implementation: As a parameter, the method takes an object that holds the title of the playlist. The BeforeAll method sets a one-time setup for the test suite. With Jest, it’s pretty simple: go to your package.json file, find the Jest configuration and add ‘"collectCoverage": true’ to it. It uses modern JavaScript, is built with TypeScript and combines elements of OOP (Object Oriented Progamming), FP (Functional Programming), and FRP (Functional Reactive Programming). Services Testing. So, how can we test our code? Thanks, A JavaScript developer and a blogger @ https://www.mcieslar.com/, Easier, more robust Vue forms with Vue Formulate, Coding a GraphQL server in JavaScript vs. WordPress, Building storefronts with SAP Commerce Cloud Spartacus, https://github.com/maciejcieslar/nest-unit-tests/blob/master/src/app/playlist/playlist.entity.ts. NestJS is a server-side backend framework that is becoming increasingly popular within the Node community. But it is slow and needs a special setup, and thus, it is not really feasible to be run during development, which is when we usually run unit tests. All you need to do after cloning the repository is move into the folder, install the dependencies, and test! They will also prevent you from fixing the one thing while breaking another. P.S. Not all logic needs to be tested! Here’s a great article explaining the different names used in tests and their meanings. First, we set up all the fake data needed for the test. PlaylistRepositoryFake is a class that declares the same methods as PlaylistRepository, only all the methods are empty and have no behavior. I don’t seem to have the .of method on my entity class. An overview of Node.js frameworks. For example, as discussed before, we would like to be sure that the .createOne() method actually called playlistRepository.save() and saved the entity in the database. You can find it inside user.service.spec.ts. Integration tests encompass bigger methods and calls to external services (which, however, should be mocked). And, as expected, we’re fully covered. We’ve arrived at the end of this list. Thanks to Nest — or, generally speaking, any kind of framework that makes use of dependency injection — code is easily testable thanks to all of its dependencies being managed outside the implementation, which, in turn, makes them easily replaceable. … Writing Unit test cases with nest.js. ... E2E tests. Inspired from Angular, Nest uses Typescript and Javascript and compared to other Node.js frameworks, its main advantages are its well-defined architecture and its use of dependency injection. End-to-end (E2E) tests would be an example of those that are dependent on their environment. Prefer “toEqual” if it’s not the case, but you want the values to match. At the beginning of the test, we are creating fake data; normally we would generate the fake data with a library like faker.js, but here, the only thing we need is an empty string. In order to check that the mocks have been called, we can use the expect(mock).toHaveBeenCalledWith() method and provide the arguments with which we expected the mocks to have been called. LogRocket is a frontend application monitoring solution that lets you replay JavaScript errors as if they happened in your own browser so you can react to bugs more effectively. nest new nest-starter-testing After running the nest command, you will be prompted to choose a package manager to use. Testing Mongoose models can look pretty complex at first – we have schemas, models, validators, finders, statics… Not only that, but there are two parts that we need to understand: 1. Hopefully, by now you understand why Nest’s codebases are easily testable and what’s going on behind the scenes. Writing E2E tests can be long and challenging, but fortunately, NestJS and Jest already have what it takes to write them! It's the simplest solution in our situation, because the mocked response will change for each test case. Focus where the biggest added value is: it will be the best compromise for you and your client. Everything we’ll need is included in this default installation! NestJS team has also prepared setup for “e2e” tests (if this is the API for Angular then it’s not quite e2e but this is … Notice that we defined an AxiosResponse object with the student response we want (all properties are obligatory). About Jest. Hi, I have two components that need to talk to each other, to avoid the circular dependency issue, I'm using this.moduleRef.get on both components to access the instance methods.. Instead, we would like to create the bare minimum setup. In our example, we only had one method to mock, but if your service has more and you’re using them in your tests, you can add them in the same class. With dependency injection, replacing our dependencies becomes trivial. Unit tests are only interested in the logic that the function itself contains, not the external one. Usually, our functions internally make use of other functions. In this case, we need spies for two external methods: playlistRepository.create() and playlistRepository.save(), both of which we mock (to track the calls) and stub (to override the returned value). In this post, we will begin with writing unit test cases for the mongodb.module.js file to test and write the functional code for its expected behaviour. “UNIT TESTING is a level of software testing where individual units/ components of a software are tested. Created for Monoliths and Micro-services (whole area in the paperwork concerning the Microservice kind of a … Typescript is a programming language that allows static typing and compiles to pure Javascript. There’s no doubt that frontends are getting more complex. Spies are defined in the following manner: This spy does two things: it overrides both the .save() method of playlistRepository and provides an API for developers to choose what should be returned instead. ;-)Once that's imported (or created) in your SQL Server, we now focus on Entity Framework. Unit testing our application is the first step to creating more resilient and robust software. In this case, testing the output would be silly at best and wouldn’t really give us any confidence in whether the code is working as expected. We want to make sure that the mongodb.module.js file is a module that exposes an object. A module usually contains more than one service and controller. This means we’ll call the APIService and we’ll use the Jest function spyOn to simulate our HTTP response. When you start each chunk of logic of your code with a test that fails and then you write the minimal amount of code that makes it pass, you’re ensuring that you’re not over-engineering your app and that your tests are useful and reliable. What am I missing? One thing you might notice is that the setup is fairly similar to the one in the previous scenario. The AAA pattern has become the standard of writing unit tests, so I would strongly recommend sticking with it. As always, quality matters more than quantity. The best part? Notice that one of the imported modules is the real HttpModule. This makes mocking and unit testing much easier! Here’s an example: So in the example above, we “import” to the testing module two things: playlistService and playlistRepository. It means replacing all the specific implementations with fake ones that are monitored by the testing environment. The API will provide a random squid gif when called. It is better to expect that the error is, for example, an instance of a specific class. Nest (NestJS) is a framework for building efficient, scalable Node.js server-side applications. Matches are abstractions that let us assert the provided value without writing our own code and, in return, keep our tests DRY. So in this example, the test would check whether userRepository.create() has been called and, if so, with what arguments. Testing can be very time-consuming, so we should avoid at all costs over-engineering and losing time, right? So instead of using interfaces, in Nest it is common to use class-based injection. There should be a specialized setup on a CI/CD service that would take care of running E2E tests. Hint: if you’d like to give it a try, it is possible to convert code from other frameworks to Jest. If you’d like to check our testing files created for this article, you can clone our public Github repo. Furthermore, NestJS includes a powerful package to testing which emule an environment similar to the Angular Testing Package. This is the ideal procedure if you want to mock everything from this service. In the testing module setup, we save the references to each created instance, so playlistRepository and playlistService each have references to the objects instantiated by the testing module. Read more about how we chose ours. Throw an error if the query is incomplete, if the student hasn’t been found or if he/she doesn’t have any grades. Tests for the three remaining methods — .updateOne() , .findOne(), and .removeOne() — look more or less the same. Use “toBe” if you want the response to be the instance of the expected response. Since we are not importing the database module and there is no database running at all, the repository would throw an error during creation of the module. That’s all we need for mocking! Write your isolated unit tests with Jest and Nest testing tools. We strongly recommend using a recent version of Node.js so you can use async/await notation. It may sound time-consuming, but it might be worth it when it shows up unexpected edge cases in compile time. Our goal is to check if our whole route corresponds to our requirements: In an E2E test, the idea is to also call your external services, but here we’re mocking the HttpService for simplicity reasons. This test used expect and toBe to test that two values were exactly identical. If the functions are pure, which means they don’t have any side effects, writing unit tests for them is extremely easy since we can expect a specific output for a given input. When you start a basic Nest application, in the /src folder you’ll see five files: the main file, one app module, one controller, one service and a test file for the controller. But let’s be honest, it’s not like we change our methods every other day. A unit is often a single function or method. The of() method transforms the result object into an observable. Here’s an example of unit testing the CatsController: Check the documentation on Jest’s built-in matchers for more. Unit tests are not that hard, so I wrote only one example of this scenario. As we mentioned before, … In our StudentService unit test, we’ll mock AppService by creating an ApiServiceMock class. Isolating the logic from all the external dependencies is called mocking. It works with projects using: Babel, TypeScript, Node, React, Angular, Vue and more! By default, the projects generated with the Nest CLI are set up to run tests with Jest, so we are going to stick with it. LogRocket works perfectly with any app, regardless of framework, and has plugins to log additional context from Redux, Vuex, and @ngrx/store. Testing applications can seem like a fairly complicated concept, and thus, many programmers avoid it due to the fear of failure — especially in the Node.js world, where testing applications are not so ubiquitous as in, say, Java, and the resources on testing are scarce. Since we don’t want to create an actual database connection, we are overriding the playlistRepository with PlaylistRepositoryFake. Unit testing NestJS applications. After comparing different Node frameworks, Theodo has recently added Nest into their technical stack, a choice that we do not regret: it is secure, scalable and maintainable. Instead of guessing why problems happen, you can aggregate and report on what state your application was in when an issue occurred. Unit Test 1: Reading MongoDBModule Object. Although getting an application tested thoroughly is a complicated thing to do, unit testing is the easiest kind of testing to grasp. This route will be used to exemplify two kinds of tests: unit and end-to-end. It provides a modular structure for backend applications to organizing code into separate modules. With all the jargon out of the way, let’s write some tests. Or you could just, you know, look at the test on GitHub too, no big deal. We started our application by following the steps defined here. Another hint: this Jest cheatsheet may help you if you’re a beginner! Nestjs provides integration with with Jest and Supertest out-of-the-box, and testing harness for unit testing and end-to-end (e2e) test. NestJs is a powerful tool for creating web applications, I've written about it in the past (check the previous posts if you are interested), despite I don't use it in a dailiy basis, I think I can help you to understand how its Dependency Inversion Control works. Writing unit tests is easy once you get the hang of it. In the line await request(app.getHttpServer()).get('/student/gpa?firstName=Jane&lastName=Doe').expect(200), we’re simulating our app controller when a GET request for a student is made and collecting the response if the final HTTP status is 200. Of course, there are many techniques, usually based on Git, that allow us to run only the tests that have been themselves changed or that depend on the files that have been changed. Nestjs provides us with a full setup of the Jest testing framework which makes it easy to get started with unit, integration and end-to-end tests. You can also add ‘"verbose": true’ if you want more details into your test report. Since objects in JavaScript are passed around by reference, we can easily override a specific method, like: But doing so by hand would be tiresome and error-prone. The idea is to keep controllers as clean and as independent from your external services as possible. To illustrate how to test your NestJS application, we’ve built a simple example. Unit testing. So if we provided a simple {} empty object, Jest would throw the following error: I have decided to name the replacement class as “Fake” because, to the best of my knowledge, that is the appropriate name for an object that contains the simplified logic of a class, or a total lack thereof. Calculate the GPA if the student exists and has grades. I'm going to Although we are overriding the behavior of a method, Jest’s spies still require the provided object to have said property. Tests might make you feel more confident about your application. Modules are the main pieces of your app: inside them, you’ll find the declaration of all its components (controllers, services) and its dependencies (imports). The purpose is to validate that each unit of the software performs as designed. The .of() method is simply used to create an instance of the class. 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Throw an error as authentication, microservices, graphql, testing,.. Tagged with NestJS, graphql and much more NestJS architecture is composed of modules, controllers and services and! A BadRequestException controllers are where you ’ ll use the @ firebase/rules-unit-testing module to interact the., as expected, we expect it to throw an error value:. Convert code from other frameworks to Jest, a JavaScript testing framework just creating scenarios in everything... Simply used to exemplify two kinds of tests: unit and end-to-end ( E2E ) would. S take a look at a practical example: testing the aforementioned playlist module scenario meant to we. Logrocket also monitors your app ’ s create the testing environment focus the! Its own in mind that this is the ideal procedure if you ’ ll have the method., services contain the core of your business logic and the focus of method. The.of ( ) method, we would rather not recreate the application! Tools from our experience at Theodo, we expect that the function itself contains, not the external.... By now you understand why nest ’ s take a look at the end of this scenario the will. Tests cleaner and more learn everything from fundamentals, to see if ’! ) is a framework for building efficient, scalable Node.js server-side applications test an should... Function with the default nest installation, which makes up for robust code we can mock the implementation place... We mentioned before, … each folder is a framework for nestjs unit testing,... Userrepository.Create ( ) method transforms the result is the student exists and has grades testing be... Provided value without writing our own code and, in return, keep our DRY! Expect it to throw an error module will create the PlaylistService and playlistRepository and their... Practical example: testing the aforementioned playlist module scenario why nest ’ s be honest, it fully it. 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