How to debug unit tests written in Typescript with Mocha from Visual Studio Code

Question

I write a Typescript library. The unit tests are also written in Typescript using Mocha framework. I'd like to execute the unit tests directly without compiling into javascript. This works with this command:

./node_modules/mocha/bin/mocha  ./test/*.test.ts  --require ts-node/register

I try to debug the unit test from Visual Studio Code with the following launch settings:

{
    "type": "node",
    "request": "launch",
    "name": "Mocha Tests",
    "program": "${workspaceRoot}/node_modules/mocha/bin/_mocha",
    "args": [
        "--require",
        "ts-node/register",
        "${workspaceRoot}/test/*.test.ts"
    ],
    "internalConsoleOptions": "openOnSessionStart"
}

This way I can debug Mocha itself from VS Code, but not the unit tests. Mocha spawns separate processes for the tests and the debugger can not automatically attach to the child processes.

What is the right way to debug Typescript unit tests from Visual Studio Code?

Answer 1

updating this thread to the config that worked for us (note to self).

• the --compilers option in https://stackoverflow.com/a/44999572/147530 is deprecated
• ts:ts-node/register gives error
• adding "${relativeFile}" also gives error Unexpected token / in JSON at position 6 as the "${relativeFile}" resolves to .vscode/launch.json .

updated config

{            
            "name": "mocha tests",
            "type": "node",
            "protocol": "inspector",
            "request": "launch",
            "program": "${workspaceRoot}/node_modules/mocha/bin/_mocha",
            "stopOnEntry": false,
            "args": [ "-r", "ts-node/register", "${workspaceRoot}/test/**/*.spec.ts", "--no-timeouts"],
            "cwd": "${workspaceRoot}"
}

Answer 2

If anybody finds it useful, the following launch.json configuration snippet is working for me without any workaround:

    {
    "name": "mocha tests",
    "type": "node",
    "protocol" : "inspector",
    "request": "launch",
    "program": "${workspaceRoot}/node_modules/mocha/bin/_mocha",
    "stopOnEntry": false,
    "args": [ "--compilers", "ts:ts-node/register", "--no-timeouts", "${relativeFile}"],
    "cwd": "${workspaceRoot}"
    }

Works fine for me with node v7.10.0, typescript 2.4.0 and Visual Studio Code 1.13.1 . Both mocha and typescript are installed locally under node_modules.