Jest offers a lot of functionalities for mocking functions and spying on them. Unfortunately, there are some pitfalls we need to watch out for. In this article, we explain how spying on functions works. We also explain how and why we should reset our mocks. Creating mock functions The most straightforward way of creating a […]
Our applications sometimes have features that allow users to choose files from their machine. Also, we might allow the users to download various files. Testing that with Cypress might not seem straightforward at first. In this article, we build a simple React application that allows the users to choose a JSON file from the hard […]
One of the most crucial things about writing tests is that they should be deterministic. A particular test should always succeed or always fail. To achieve that, we sometimes need to mock parts of our environment when testing. A good example can be a function that relies on pseudo-random numbers. Besides the above, we also […]
Every automated test that we write should be deterministic. One of the things we need to do to achieve that is to make our frontend tests independent of the backend. Besides mocking REST API requests, we also need to learn how to mock a WebSocket connection. In this article, we create a simple backend application and […]
With code coverage, we can measure the percentage of our code that runs with our test. In this article, we learn how to measure our coverage and discuss whether it is a metric worth considering. We will understand its benefits and limitations and see how a high code coverage can mislead us into thinking that […]
Unit testing is handy for testing how our React components behave when the user interacts with them. However, this might not be enough. Besides testing the logic behind a particular component, we should also test if our user interface changes unexpectedly. We can use snapshot testing to detect unintended modifications to how our components render. Introduction to […]
With End-to-End testing (E2E), we test a fully working application where different parts of our application work together in real-life scenarios from start to finish. The End-to-End tests might also act as regression tests that check if our latest changes haven’t broken any previous features. We might also use them as smoke tests that ensure […]
Our applications sometimes include features that allow users to select files from their hard drives, and some functionalities might let users download files. Implementing End-to-End tests that ensure that everything works as expected might not seem straightforward at first. In this article, we create a simple React application that lets users choose a JSON file […]
