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Mocha Testing: The Java in Your Script

Mocha Testing: The Java in Your Script

Matt Williams's photo
Matt Williams
·Jan 5, 2023·

4 min read

Mocha Testing: The Java in Your Script was initially published on Thursday January 05 2023 on the Tech Dev Blog. For the latest up-to-date content, fresh out of the oven, visit https://techdevblog.io and subscribe to our newsletter!

Hey there! Are you ready to learn how to rock the Mocha JavaScript testing library? Great! Mocha is an incredibly powerful and flexible tool for testing your JavaScript code, and in this tutorial, I'm going to show you some of the best ways to use it.

Getting Started

First things first, let's make sure you have Mocha installed. If you're using npm, you can just run the following command:

npm install --save-dev mocha

Now that we have Mocha installed, let's create a simple test file. I like to keep my tests in a separate directory, so let's create a "test" directory in the root of our project. Inside the "test" directory, create a file called "test.js".

Our first test

In this file, we'll start by requiring Mocha and creating a simple test suite. A test suite is a group of related tests that test a specific aspect of your code. Here's an example of a simple test suite:

const mocha = require('mocha');
const assert = require('assert');

describe('My Test Suite', () => {
  it('should run a test', () => {
    assert.equal(1, 1);
  });
});

The "describe" function creates a test suite, and the "it" function creates an individual test. In this case, we're just testing that 1 is equal to 1 (which it obviously is).

Running tests

Now that we have a simple test suite set up, let's run it. To do this, we can use the Mocha CLI. Run the following command in your terminal:

mocha test/test.js

You should see something like this:

My Test Suite
    √ should run a test

  1 passing (9ms)

Awesome! We have a passing test. Now let's dive a little deeper and look at some of the best practices for using Mocha.

Best practices

One of the most important things to keep in mind when writing tests is to make sure they're independent. This means that each test should not rely on the results of any other tests. This is important because it ensures that if a test fails, you can easily pinpoint the problem.

To achieve independence, it's a good idea to set up and tear down your test environment before and after each test. Mocha makes this easy with the "beforeEach" and "afterEach" functions. Here's an example:

describe('My Test Suite', () => {
  beforeEach(() => {
    // set up test environment
  });

  afterEach(() => {
    // tear down test environment
  });

  it('should run a test', () => {
    assert.equal(1, 1);
  });
});

Another best practice is to make your tests as descriptive as possible. This makes it easier to understand what each test is doing and why it's important. To make your tests more descriptive, you can use the "describe" and "it" functions to create nested test suites and tests. Here's an example:

describe('My Test Suite', () => {
  describe('Test Sub-Suite', () => {
    it('should run a test', () => {
      assert.equal(1, 1);
    });
  });
});

Finally, it's a good idea to use assertions whenever possible to ensure that your tests are reliable. Assertions allow you to compare the actual value of a test to the expected value, and if they don't match, the test will fail. Mocha support Node.js' built-in "assert" module, which provides a variety of assertion functions, such as equal, strictEqual, and deepEqual.

Node.js assertions

Let's take a look at some of the most useful Node.js assertions.

equal

This function compares two values for strict equality. If the values are not equal, the test will fail. For example:

it('should test for strict equality', () => {
  assert.equal(1, 1); // this test will pass
  assert.equal(1, 2); // this test will fail
});

strictEqual

This function is similar to equal, but it also checks for type equality. For example:

it('should test for strict and type equality', () => {
  assert.strictEqual(1, 1); // this test will pass
  assert.strictEqual(1, '1'); // this test will fail
});

deepEqual

This function is used to compare two objects or arrays for deep equality. This means that all properties and values of the objects or arrays must be equal. For example:

it('should test for deep equality', () => {
  assert.deepEqual({a: 1, b: 2}, {a: 1, b: 2}); // this test will pass
  assert.deepEqual([1, 2, 3], [1, 2, 4]); // this test will fail
});

Conclusion

There are many other useful features and best practices when it comes to using Mocha, but these are some of the most important ones to get you started. With a little bit of practice, you'll be a Mocha pro in no time! Happy testing!

Mocha Testing: The Java in Your Script was initially published on Thursday January 05 2023 on the Tech Dev Blog. For the latest up-to-date content, fresh out of the oven, visit https://techdevblog.io and subscribe to our newsletter!

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