nyc VS Sinon.JS

Native code coverage via v8 or istanbul.

Writing tests is essential, and knowing whether you test all the required cases for your logic is even more critical. The most common testing coverage tool is Istanbul, where you can see how well your tests exercise your code by lines, functions, and branches. Below is an example of how the test coverage report looks in your terminal:

Here is a quote from istanbul, one of the most used code coverage tool:

Unit testing framework was already implemented, using Vitest so I started hacking by setting up a coverage provider to explicitly identify the covered/uncovered lines and mentioned this to the maintainer in the comments. I used Istanbul 🇹🇷 for this purpose.

Your project probably has a coverage report. If you’re using Jest as your unit test runner, generating a coverage report is embedded in it. It is done with Istanbul under the hood, which generates a nice HTML page presenting the entire project unit test coverage.

> This is a rant written by someone with just enough understanding to be dangerous, but not quite enough wisdom to know why things are still the way they are. Most of the complaints raised are subtly inaccurate.

Author seems aware of CAP_NET_BIND_SERVICE: https://source.small-tech.org/site.js/app/-/issues/169 and https://github.com/istanbuljs/nyc/issues/1281 – the "side effects" are NodeJS explicitly checking for it, so that's a NodeJS thing and not a Linux thing.

Yet curiously it's completely unmentioned in this article, in spite that this is probably what started the author's dislike of privileged ports. I guess it was inconvenient as it got in the way of angrily ranting.

This approach will create two json coverage files, which will be merged together by NYC. Therefore the results will be purely local. If You don't mind using online tools like Codecov or Coveralls for merging data from different tests, then go ahead and use them. They will probably also be more accurate. But if You still want to learn how to get coverage from E2E, then please read through

https://istanbul.js.org/ measures how much of your code is covered by tests

Jest uses a package called Istanbul to provide test coverage metrics such as statement, branch, function, and line coverage so that you can understand and enforce the quality of your test suite, providing more confidence in releases.

So let’s see if nyc (the code coverage generator) can help with that. Hmm… this documentation seems interesting! So basically what I understand from it is that I need to collect all the reports from the different packages and then run the nyc report over it. The flow should be like this:

If you are using a mocking library, such as sinon, jest-mock, or ts-mockito, make sure that it is compatible with Jest. You may need to install additional packages or configure them in your configuration file. For example, to use sinon with Jest, you can install the sinon-jest package and add the following to your configuration file:

Mocha is a test runner, Chai is an assertion library, Sinon is a mocking library, this normally the combination you would need to use if you choose mocha, but there are others.

Instead, use pure functions + dependency inject your stubs (e.g. parameter to function). Also note, no need for Sinon or some other test double library. JavaScript is so good nowadays to easily make objects/classes/functions or any combination thereof on the fly that are terse.

I've had some good experiences with Ava + Sinon. I've personally disliked Jest because it seemed to do some weird trickery in the background that prevented me from using ES modules.

🤖 You can use the Mocha testing framework with the Chai assertion library to write tests for your Express controller. You can also use the Sinon library to mock the database calls. This will allow you to test the controller without actually making a call to the database. You can also use the SuperTest library to make HTTP requests to the controller and test the response.

You can use sinon js to create a mock version of your http library (axios) that responds with the data you’re expecting.

Assertions are the checkpoints of our test block that confirm if an automated test has passed or failed. Cypress bundles the Chai, jQuery, and Sinon.JS libraries for assertions. They check the desired, expected application in which the test is running. A complete listing of assertions can be found in the documentation here.

ES module is basically a "class" that you inject dependencies into through imports. And for tests you just use something like sinon to swap module dependencies for mocks.

You can use a tool like sinon to pass in your own function instead of the real moment library. From there you can write tests that ensure moment was invoked appropriately.

Let's configure tests with mocha, chai and sinon on Typescript in a few steps.