Testing pull request dondi/GRNsight#640. Let’s use this example test to introduce the basics of mocha, mocha-webpack, and vue-test-utils. build ES6 modules, production code and unit tests, modify karma/lib/middleware/karma.js#L35 to set the type of the script tags to module, modify karma/lib/middleware/karma.js#L129 to also host another javascript that can be loaded as a module by the contect.html and debug.html runners. Mocha has a nice support for asynchronous tests we could tap into if we were testing the new onIncreaseFromHttp method directly, as we could chain our assertions directly into the promise chain: You can read more about the support for asynchronous testd in mocha in its docs. Mocha.js provides two helpful methods: only() and skip(), for controlling exclusive and inclusive behavior of test suites and test cases. Figure 7: comparing mocha tests VS mocha-webpack vue tests. Here is an example for the import statement with type module. It looks like this error was hiding the other ones mihirsamdarshi mentioned this issue May 29, 2018. Suppose you have two JavaScript files: index.js and test.js. The test file sum.test.js turns into a module that imports function and performs test: Because test file now imports source file, the HTML page can include only test file, not both files as before. How to handle ES6 modules using the import/export syntax. We can now update the earlier tests for the increase button/method and verify the increased event was emitted as expected: Note: you might be wondering what is the difference between to.be.equal() and to.be.eql(). I have created an overview of the different ways by which a module can be exported, together with their corresponding import syntax. Let’s create a simple component with a counter and a button to increase it, that we can use as the target of the next tests. Imagine your component uses the current route in some method or computed property: We can just create a mock route object and inject it on the call to create the instance: Now let’s see how we can deal with the router. Learn more, We use analytics cookies to understand how you use our websites so we can make them better, e.g. It returns a wrapper that you will use to interact with your component and the virtual DOM it’s being mounted, for example triggering events or inspecting the resulting html. {{ (>_<) }}This version of your browser is not supported. The following tests showcase this, and to make them more interesting they also show how common test initialization can be moved into a beforeEach test hook: Our component binds an event handler to the click event of the button that increases the counter. Until now we have managed to test our component in isolation by instantiating them with the shallow function and providing any input prop data. That’s why our test method accepts a done parameter and wraps the execution of the assertion in a call to setImmediate. Are you keeping up with new developer technologies? Please check the documentation, and if it is inadequate please send a fix. they're used to gather information about the pages you visit and how many clicks you need to accomplish a task. In this tutorial, we are going to learn about how to solve the cannot use statement outside of a module error in browser. modify the contect.html and debug.html runners to not kickoff karma with an inline line, but place that line in a separate JS file, which is loaded as a module and therefore after all the other scripts for testing frameworks and tests: add above mentioned JS file, karma\static\karma-start.js: also fix jasmine to set itself on the window in the IIFE ( separate NPM module, so will refrain from diving into its details). - The scripts defined in package.json all defer to the vue-cli-service as in: This is all fine because the vue-cli uses a plugin-based architecture in which plugins can define their own dependencies, command and webpack settings! https://developer.mozilla.org/en-US/docs/Web/HTML/Element/script, fix(common): show more detailed info about error logged in console, https://karma-runner.github.io/2.0/config/files.html, Karma Closure preprocessor to support ES6 module. The static importstatement is used to import bindings that are exported by another module. As discussed earlier, you could decide to verify how the rendered html changes as a result of the event or how the component state has changed. Learn how Behavior Driven Development (BDD) works with a real-world example of how to use it. the start of karma is too soon, as it is an inline script which cannot be deferred to until after the frameworks are loaded. Let’s begin by inspecting the Vue component we are testing, which is defined as single-file Vue component: This is a very simple component that receives an input property which is then included in the rendered html, which is exactly what we are testing. Or if the feature is incomplete, please open a detailed explanation. Figure 6: defining tests and modules with mocha. For example, some methods will be used as event handlers of events emitted by nested Vue components, which cannot be triggered when mounting components using the shallow function. [ x] 'Smoke tested' the code to be tested by running it outside the real test suite to get a better sense of whether the problem is in the code under test, your usage of Mocha, or Mocha itself [ x] Ensured that there is no discrepancy between the locally and globally installed versions of Mocha. Does anybody managed to get it working with imports from node_modules? Client-side testing with modern frameworks like Vue gets even more complicated due to the number of tools/libraries involved. However, when you run npm run serve, the app is bundled with webpack and served with the webpack-dev-server! In this callback, you can also define submodules by adding further calls to describe. The name parameter is the name of the \"module object\" which will be used as a kind of namespace to refer to the exports. It is very similar to the fact the browser wouldn’t understand the source code as is written and needs the webpack bundles to be generated in a format the browser can understand. All rights reserved. If this cannot be fixed within the short term, perhaps this could be taken care of by a custom karma middleware plugin for now? This shouldn’t stop you from testing any component method as you can invoke them directly through the reference to the component instance as in wrapper.vm.methodName(methodArgs). This is where vue-test-utils fits the puzzle. Which means in our test we can replace the library with a mock as in: Where the first parameter to the rewire function should match the name of the variable and not the string used with the import statement! It then registers any new commands provided by them (so they are available in the CLI) and their hooks which extend the default webpack configuration. Thanks, reproduced. This should all sound familiar as it is the same across most test frameworks. The unit test fails at the import statement on the component and returns this error:? Example, given we have the following folder structure including. Even if you are not using the vue-cli, you should still find the information relevant once you manually setup mocha-webpack and vue-test-utils. How to load .vue files. Also seen confused: named imports != destructuring # Community Question @Kevin: Hi, this only works in node or something like that? This way the component is tested in isolation and the tests are faster since it doesn’t need to update and render the entire component tree. Make sure you npm uninstall each one to remove them from node_modulestoo. Sorry for the confusion, I am still new to configuring karma (used it with Angular only so far) and seeing that issue open made me think I am doing it correctly - my mistake, I wasn't :). Next update the Counter.vue component with a new button and associated method where the counter is increased according to a json response from an HTTP request: In order to test the behavior of the new button, we need to mock the $http property of the component instance so it doesn’t try to send a real HTTP request and instead uses some predefined behavior. Let’s suppose a certain action triggers some programmatic navigation in your component: It’s equally straightforward to create a sinon spy (since we just want to track the received calls) and create a test where we verify the expected navigation was invoked: Many other Vue libraries and plugins follow the same idea of injecting methods and properties into the component instance, like vuex which injects the $store property. When we write unit tests using mocha-webpack, we are still using the mocha testing framework to define our tests. Our component is directly loading the library with import axios from 'axios', so we need a different strategy: As usual, start by installing the library: Then, make sure you enable it on your .babelrc file, exclusively for the test environment: Now the plugin is wired and every time we import a Vue component (or any other file) a function named __Rewire__ lets you replace any dependency loaded through an import statement. This is the reason why the tests need to be run using mocha-webpack instead of directly using mocha and the reason why we can use ES6 modules (import/export) and import .vue files, while still running the tests in a Node.js environment As any other framework, it provides functions to define a test module and each of the individual tests: - The function describe allows you to define tests grouped into modules. You can check for yourself if you open the source code of the main Service object of the @vue/vue-cli-service and inspect the list of default plugins which at the moment looks like: Where each of the command files contains the definition of the command itself (i.e., its name and options) and the function invoked when running the command. In previous versions, you could also use the inject-loader but this no longer works, so be careful when you read some “old” 2017 tutorials. But as I hope the second half of the article has shown, once the basic setup is in place, writing tests for your Vue components is a surprisingly pleasant and straightforward experience. Uncaught SyntaxError: Cannot use import statement outside a module. For example, you could directly invoke the method bound to the increase button with wrapper.vm.onIncrease(). Unit testing with Vue.js (using vue-test-utils, mocha-webpack and the vue-cli), Error Handling in Large .NET Projects - Best Practices, Behavior Driven Development (BDD) – an in-depth look, Aspect Oriented Programming (AOP) in C# with SOLID, JavaScript Frameworks for ASP.NET MVC Developers, www.dotnetcurry.com/javascript/1349/introducing-vue-js-tutorial, The Absolutely Awesome Book on C# and .NET, Managing Vue state in Vue.js applications with Vuex, .NET 5 - What you need to know about the latest .NET, Progressive Web Applications – From Zero to Hero (Blazor, ASP.NET Core, Vue.js, Angular Examples), Application Architecture – Getting started, Migrating Code to Azure DevOps Repos (4 Different Scenarios), Demystifying Pipelines in Azure DevOps (Build and Deployment), Using Azure DevOps for Product Development (Multiple Teams), Coding practices: The most important ones – Part 2, Azure Cognitive Search – Using Search APIs in an Angular Application, Memoization in JavaScript, Angular and React, Source Control in Azure DevOps (Best practices), Architecting .NET Desktop and Mobile applications, Angular 9 and Angular 10 Development Cheat Sheet, Selected features: Router, Vuex, Linter, Unit test, Vue and related libraries like vue-router or vuex, the various loaders and webpack plugins like vue-loader, css-loader or uglifyjs-webpack-plugin (just to name a few). The project generated by the vue-cli includes a simple unit test for one of the Vue components in the project. This section assumes some basic knowledge about modules. He started his career as a Microsoft developer focused mainly on .NET, C# and SQL Server. It would be great to have this implemented. This is a 500 pages concise technical eBook available in PDF, ePub (iPad), and Mobi (Kindle). - The dependencies listed in package.json do not include the expected webpack, webpack-web-server, various webpack loaders, and mocha-webpack. { pattern: '*.js', type: 'module', ...}. Learn more. 3. So far there is nothing new to someone who wrote tests for Node.js applications using mocha and chai. We use optional third-party analytics cookies to understand how you use GitHub.com so we can build better products. C# and .NET have been around for a very long time, but their constant growth means there’s always more to learn. , and next one. On the other hand, the mount method will create an instance of every child component, include them in the component tree and include its rendered output in the virtual dom. Installing the vue-cli is as simple as running the following command in your favorite shell: Once you have the cli installed, you can start the process for creating a new project by running its create command: You will immediately get prompted with the first option of the creation process, which once completed will create the project inside the specified folder (defaulted from the project name, as in ./unit-test-example in the example above). Dismiss Join GitHub today. The first thing you should know when using sinon is that they have split the api for creating stubs and spies. By default, this test is located in $/test/unit/HelloWorld.spec.js and it is unit testing the component $/src/components/HelloWorld.vue. We use essential cookies to perform essential website functions, e.g. Feedback - Leave us some adulation, criticism and everything in between! Let’s update the onIncrease method of our simple component to emit an increased event: The wrapper provided by vue-test-utils also provides a handy way of verifying that the expected events were emitted by the component you are testing. 4. When I tried to reproduce the first example in Vanilla JS, always say the same error: SyntaxError: Cannot use import statement outside a module. Even worse, it only knows about relative module imports, and we are using paths from the source code root as in import HelloWorld from '@/components/HelloWorld.vue'; This API exposes the shallow method, which allows you to instantiate the HelloWorld.vue component into this virtual DOM. ES Modules are coming to NodeJS. This way, testing a computed value is as simple as asserting that the value of the wrapper.vm.computedName is as expected. The test command invokes mocha-webpack and provides the default arguments for it like the test file pattern (defaulted as test/unit/**/*.spec.js) and where to find the webpack configuration. You signed in with another tab or window. In the latter half of his career he worked on a broader set of technologies and platforms with a special interest for .NET Core, Node.js, Vue, Python, Docker and Kubernetes. Merged 0 of 11 tasks complete . In such a case, you will need to manually install and configure all the required dependencies, including: Then you will need to wire the scripts for generating webpack bundles for production and generate/serve them for local development. 5. Based on your screenshot ... you are using Java code in a JavaScript file.... Those are 2 different languages. The fact that half of this lengthy article is dedicated to explaining how things are setup and work under the covers, is a testament to that. Figure 7: comparing mocha tests VS mocha-webpack vue tests, This is the reason why the tests need to be run using mocha-webpack instead of directly using mocha and the reason why we can use ES6 modules (import/export) and import .vue files, while still running the tests in a Node.js environment. However, by their own nature, computed properties depend on either the current component state or other properties. As such it is outside the scope of this article which is to show how to write and run Vue unit tests using vue-test-utils and mocha-webpack. Like with CommonJS, each file is its own module. However, testing your component rendered output might make your tests more brittle and dependent on the templates which tend to be modified more frequently. Node has a core module called ‘fs’:As you can see, we imported the “fs” module into our code. You should now be able to: - Run the npm test command and see an example unit test passing. Go to karma/node_modules/karma-browserify/lib/preprocessor.js and change: var preprocessor = require('karma/lib/preprocessor'); I am not sure though, I could not find any clear documentation on this subject yet. You can read more about this rationale in the vue-test-utils docs. Some useful links: node.js's own documentation. Successfully merging a pull request may close this issue. In my case I'm using nextJs, and I solved my problem removing "next/babel" preset when I'm on Test enviroment (For any reason, using "next/babel", console shows the error: "SyntaxError: Cannot use import statement outside a module"): Mozilla has some nice documentation about import The @vue/vue-cli-service installed inside node_modules is loaded. { pattern: '*.js', type: 'module', ...} We use optional third-party analytics cookies to understand how you use GitHub.com so we can build better products. The export parameters specify individual named exports, while the import * as name syntax imports all of them. We at DotNetCurry are very excited to announce The Absolutely Awesome Book on C# and .NET. Pastebin.com is the number one paste tool since 2002. Editorial Note: If you are new to Vue.js, here’s an introduction www.dotnetcurry.com/javascript/1349/introducing-vue-js-tutorial. You can also specify test suites and test cases that should or should not be run. privacy statement. Use import for ES6 modules and require for commonJS. For more information, see our Privacy Statement. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. It’s also worth mentioning that mocha doesn’t care which assertion library you use, any library that throws instances of “Error” will be ok. That’s it, the project is ready for us to start adding more code and writing tests for it! Below are examples to clarify the syntax. Wiht most browsers landed ES6 modules in their current releases ( https://caniuse.com/#feat=es6-module ), it would be nice to still be able to unit test this javascript in all these browsers using karma, without transpilation. Organized around concepts, this Book aims to provide a concise, yet solid foundation in C# and .NET, covering C# 6.0, C# 7.0 and .NET Core, with chapters on the latest .NET Core 3.0, .NET Standard and C# 8.0 (final release) too. Thus, providing a sinon stub for the this.$http component property is as simple as providing the mock in the shallow/mount call: Now we have everything we need to verify the behavior of the new button which increases the counter by the number of objects in the HTTP response array: The main change with the previous test is that now our test is asynchronous as it depends on a Promise being resolved (even if we mocked this.$http.get it still returns a Promise). If you are going to write tests in a JavaScript environment, it is really worth getting used to it. To do so, I modified the following: Please submit your fix as a pull request so it goes through all of the prerequisite testing. Before you start, you'll want to update to the latest version of Polymer CLI. As modules support special keywords and features, we must tell the browser that a script should be treated as a module, by using the attribute