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#30daysofVue - Day 26 - Implementing Tests

Implementing Tests In Vue.js

There are multiple testing tools available for testing your Vue application. The popular choice is Jest. It offers us a zero-configuration setup. The Getting Started guide in the Jest documentation shows us that we need to install the Jest package, create a .test.js or .spec.js file, and add a test script to the package.json file.

However, if we select the Jest suite as a dependancy, we want in a Vue CLI scaffolded project - this setup would already be prepared for us. The Vue CLI introduces a tests/ directory adjacent to the src/ directory for a scaffolded project that has either the 'Unit Testing' or 'E2E Testing' option selected during manual setup.

The tests/ directory will contain either the unit/ or e2e/ folders depending on which testing environment was selected during the Vue CLI setup stage. In our case, only a tests/unit/ folder will be created which would contain an .eslintrc.js file and an example.spec.js file.

Jest provides a few native methods that we'll be using. Both of the following methods accept two arguments, the first being a description string and the second a function to execute:

describe()

it()

In Jest, the it() function is sometimes aliased to test().

The describe() function provides a way for us to group our tests together in logical bundles.

We can add our first test using the it() function which is the function we can use to set our expectations.

The Vue CLI package sets up a quality testing environment using Jest (if selected) automatically for us. We can execute all our tests by using the test:unitscript declared in thepackage.json file.

npm run test:unit

EXPECTATIONS

Jest provides a few global commands in our tests by default (i.e. things you don't need to require). One of those is the expect() command. The expect() command has a few expectations which we can call on it.

The expect() function takes a single argument: the value or function that returns a value to be tested. For instance, our two tests we've already written pass the boolean values of true and false .

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