#javascript #jest #node #testingJest explicitly or arbitrarily force fail() a testWhen testing code with Jest, it can sometimes be useful to fail a test arbitrarily. This post goes through a few scenarios where that might be useful and how to fail a Jest test explicitly/in a forced manner. It also presents more idiomatic Jest patterns that could be used interc ...
#javascript #jest #node #es6 #testingJest Full and Partial Mock/Spy of CommonJS and ES6 Module ImportsJavaScript import/require module testing do’s and don’ts with Jest The example repository is available at github.com/HugoDF/mock-spy-module-import. This post goes through how to achieve different types of module mocking scenarios with Jest. From simple Import interc ...
#jest #javascript #node #testingHow to run, ignore or skip Jest tests, suites and filesWhen debugging or writing units tests with Jest it can be useful to specify a single file or test to run or to exclude a specific failing test for the Jest run. This post goes how to skip and exclude a single test, a whole Jest test suite and a whole Jest test file using the CLI ...
#jest #javascript #node #testingHow to run Jest tests sequentiallyBy default Jest runs tests in parallel with a “a worker pool of child processes that run tests” (Jest CLI docs). As per the Jest documentation, running tests in sequence (serially), can be helpful for debugging purposes and for test run performance reasons. ...
#javascript #jest #testing #nodeJest ignore or exclude file/function/statement from test coverageIn computer science, test coverage is a measure used to describe the degree to which the source code of a program is executed when a particular test suite runs. Code coverage - Wikipedia Code coverage is usually used as a quality metric for software eg. “Our code has to have 80 ...
#JavaScript #jest #Node #Testing #dateMocking/stubbing the current Date in Jest testsThere are situations where new Date() or Date.now is used in application code. That code needs to be tested, and it’s always a struggle to remember how to mock/stub or spy on Date.now/new Date with Jest. This post goes through multiple approaches to mocking, stubbing and spying o ...
#javascript #node #jest #testing #MongoDBAvoiding recursion pitfalls: MongoDB nested query clause addition and removalA case-study on where recursion can be useful for enterprise Node.js applications and how to avoid its common pitfalls like RangeError: Maximum call stack size exceeded. The full repository for this post is on GitHub: github.com/HugoDF/mongo-query-clause-modification We’ll ...
#testing #jest #node #javascript #jestJest assert over single or specific argument/parameters with .toHaveBeenCalledWith and expect.anything()With Jest it’s possible to assert of single or specific arguments/parameters of a mock function call with .toHaveBeenCalled/.toBeCalled and expect.anything(). The full example repository is at github.com/HugoDF/jest-specific-argument-assert, more specifically lines 17-66 ...
#testing #jest #node #javascript #jestJest assert over single or specific argument/parameters with .toHaveBeenCalledWith and expect.anything()With Jest it’s possible to assert of single or specific arguments/parameters of a mock function call with .toHaveBeenCalled/.toBeCalled and expect.anything(). The full example repository is at github.com/HugoDF/jest-specific-argument-assert, more specifically lines 17-66 ...
#Express #Node #jest #Testing #JavaScriptA testing guide for Express with request and response mocking/stubbing using Jest or sinonTo test an Express handler, it’s useful to know how to successfully mock/stub the request and response objects. The following examples will be written both using Jest and sinon (running in AVA). The rationale for this is the following. Jest is a very popular “all-in-one” testing ...
