Introduction
Welcome readers! In this blog, we will learn how to handle failed test cases. We will also look at the step-by-step process of setting up a debugger for Jest in VS Code and perform a sample debugging to see how it actually works.
VS Code is a code editor which comes with an inbuilt Terminal, Source Control (Git), smart completions with Intellisense, etc. VS Code is highly customizable and fast. Please go through this post if you don’t have VS Code already installed in your machine.
Let's get started. I hope you learn a lot from this article.
Debugging Failed Tests
While testing, we will eventually encounter a failed test case. Jest provides detailed information like expected and received values in matcher, line where test fails, etc.
Let’s make an example function and write a failed test for it, to understand better.
Program
// creating functions
const functions = {
function: (param) => {
return param;
}
};
//export the function
module.exports = functionsThe function is simply returning the parameter.
Test
// importing functions
const functions = require('./function.js');
// test
test('failed test', () => {
expect(functions.function(5)).toBe(4);
});In the test, we have called function with 5, which will return 5, and in the matcher, we expect it to match with 4, which is why the test will fail.
Run the test using the command npm test.
Output
As we can see, Jest specifies the line where the test fails, and it also provides what is expected in the matcher and what is received.
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