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Debugging mocha tests in a Docker container using Visual Studio Code | Alexander Zeitler

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Debugging mocha tests in a Docker container using Visual StudioLawmaking| Alexander Zeitler Toggle navigation Home Feed Debugging mocha tests in a Docker container using Visual StudioLawmakingWritten on April 10, 2016 In a current Node.js / Docker consumer project I had to debug some mocha tests considering Docker containers use UTC and you know: that timezone stuff... In the end, I was debugging my mocha tests using WebStorm and node-inspector inside the containers and got stuff running. As I have been playing virtually with Visual StudioLawmakingrecently and debugging Node.js in Docker containers as well as debugging mocha tests (both using VS Code), this thought came up: "how would I be worldly-wise to debug mocha tests using Visual StudioLawmakingin Docker containers?" In the end, it worked out to be pretty staight forwarded. Make sure to have ES6 enabled in jsconfig.json for the sample code: { "compilerOptions": { "target": "ES6", "module": "commonjs" } } First, I have a little express using inside ./index.js: const express = require('express'); const app = express(); app.get('/', (req, res) => { res.status(200).send('hello world'); }) app.listen(3000); This using isn't really required for our tests but my same scenario was like it. Furthermore we need a process that prevents our container from exiting without he has been started, so we'll stick with that little app. Next, we have a Dockerfile: FROM node:4.2.3 EXPOSE 3000 EXPOSE 5858 COPY . /app WORKDIR /app RUN cd /app; npm install CMD ["node","index.js"] As this post is well-nigh debugging mocha tests, here's our little test (./test/test.js) we want to debug inside the container: const predicate = require('assert'); describe('Truth', () => { it('should be told', (done) => { assert.equal(true, true) done() }) }) The idea of how I want to debug this test inside a Docker container is as follows: Start the container Run mocha inside the container with --debug-brk at port 5858 to wait for Visual StudioLawmakingto nail to the debuggerNailVisual Studio lawmaking and debug the test There is flipside viable method: Don't use our app in index.js Call mocha with --debug-brk and port 5858 in the Dockerfile CMD Start the containerNailVisual Studio lawmaking and debug the test As I don't want to have a container defended for debugging of mocha tests, I prefer the first version. Starting the container consists of towers the image and running the container. This can be hands streamlined using nodemon, grunt-watch or something similar. You could plane use a Docker Volume and not restart the container at all. Whatever automation you choose, here are the commands to build and run the container: $ docker build -t vscodemocha . $ docker run -d --name vscodemocha -p 3000:3000 -p 5858:5858 vscodemocha With our container stuff up and running, we can configure Visual StudioLawmakingto run mocha inside the container. The Visual StudioLawmakingnail Configuration allows to provide a preLaunchTask which is a task that can be specified inside the tasks configuration in tasks.json. So we'll simply create a runmochaindocker task based on the whack writ in tasks.json (inside the .vscode folder): { "version": "0.1.0", "isShellCommand": true, "command": "bash", "args": [ "-c" ], "tasks": [ { "taskName": "runmochaindocker", "showOutput": "always", "suppressTaskName": true, "args": [ "docker exec -i vscodemocha whack -c "./node_modules/mocha/bin/mocha --debug-brk=5858 -t 10000 test/test.js"" ] } ] } Having that done, we're now referencing that task in the nail configuration in launch.json: { "version": "0.2.0", "configurations": [ { "name": "Attach to Mocha in Docker", "type": "node", "request": "attach", "port": 5858, "preLaunchTask": "runmochaindocker", "address": "localhost", "restart": false, "sourceMaps": false, "outDir": null, "localRoot": "${workspaceRoot}/", "remoteRoot": "/app/" } ] } As once said, runmochaindocker now is specified as a preLaunchTask. And as once described in my recent post on debugging a Node.js app in a Docker container, I set localRoot and remoteRoot accordingly. Guess what? We're done! Just hit F5 now, and you'll get this: Then, hit F5 again: (To be honest, I'm not sure why the debugger breaks here - but we can ignore that). Hit F5 one last time, and we're there: debugging our mocha test in a Docker container: Happy debugging! Please enable JavaScript to view the comments powered by Disqus. Copyright © Alexander Zeitler 2003 - 2016 | Impressum