Debug a single test in Jest

Question

I have many jest tests, within many test suites, within many test files.

I need to isolate and debug a single test.

I'm debugging via node --inspect-brk./node_modules/jest/bin/jest , so other solutions involving watch mode are too complicated.

How can I skip all tests except the one I need to debug?

Answer 1

jest handles this in two steps

1. isolate your test file by running jest with the testPathPattern (jest docs) command line argument

   node --inspect-brk ./node_modules/jest/bin/jest --testPathPattern="integration.test"

   here integration.test is supplied as a regular expression to filter for the correct test file

2. isolate your test function
   there are two ways to do this

   • one way is to use the testNamePattern (jest docs) command line argument

     node --inspect-brk ./node_modules/jest/bin/jest --testNamePattern="host events"

     here host events is supplied as a regular expression to filter for the correct test suite name

   • alternatively, you can add .only to your test function:

     • so that test("object works", async() => {/*...*/})

     • becomes test.only("object works", async() => {/*...*/})

Answer 2

I am using VSCode for debugging and in launch.json add to runTimeArgs a testPathPattern as your folder name:

{
"version": "0.2.0",
"configurations": [{
    "name": "Debug Jest Tests",
    "type": "node",
    "request": "launch",
    "runtimeArgs": [
        "--inspect-brk",
        "${workspaceRoot}/node_modules/jest/bin/jest.js",
        "--runInBand",
        "--testPathPattern=<NameOfTheFolder-you-want-to-test-without-this-angle-brackets>"
    ],
    "console": "integratedTerminal",
    "internalConsoleOptions": "neverOpen",
    "port": 9229
}]
}

Answer 3

If you are using VSCode, Jest extension might come in handy.

https://marketplace.visualstudio.com/items?itemName=Orta.vscode-jest

Answer 4

https://marketplace.visualstudio.com/items?itemName=firsttris.vscode-jest-runner

Another extension. This one uses CodeLens so there are Run|Debug links above each test: