Mastering JavaScript Testing with Chai
At LogRocket, we’ve learned a thing or two about JavaScript testing libraries. In this series, we’ll explore the LogRocket testing stack and share tips and tricks for making tests faster and more robust.
Test Expectations with Chai
Chai is a popular testing library that helps you make assertions about code behavior. It comes in many syntactic flavors, allowing you to choose the one that suits your needs. For example, if you want to assert that a variable is a string, you can use the expect() function.
Handling Unexpected Inputs
As developers, we’re good at ensuring our code works when inputs are correct. However, the real challenge lies in handling unexpected or failing inputs. Chai’s throw() helper allows you to assert that code should throw an exception, making it easier to test for edge cases.
Equality Checks with equal() and eql()
Chai provides two built-in functions for determining equality: equal() and eql(). While equal() checks for referential equality, eql() performs a deep equality check. Using these functions provides more informative test output compared to using simple conditional statements.
Extending Chai with Plugins
Chai can be extended with plugins that provide additional functionality. One such plugin is dirty-chai, which allows you to write more robust assertions by throwing exceptions when syntax mistakes are made. Another useful plugin is sinon-chai, which enables you to make Sinon assertions with the Chai syntax.
Using eslint-plugin-chai-expect for Linting
If you’re using ESLint to lint your code, eslint-plugin-chai-expect can help prevent common syntax errors when working with Chai. This plugin ensures that your code is error-free and follows best practices.
Conclusion
In this article, we’ve explored the basics of testing with Chai and highlighted some of its key features. By mastering Chai, you can write more effective tests and ensure your code is robust and reliable. Stay tuned for the next article in this series, where we’ll dive deeper into the world of JavaScript testing.