Unit testing conundrum when using webpack

[frenya]

It seems to me there's one fundamental flaw when it comes to unit testing while using the suggested webpack configuration for distribution and a plain compilation using tsc for testing.

• The main attribute of package.json must point to dist/extension.js
• The code that is loaded by the extension host is therefore dist/extension.js even when unit testing
• Any module you reference in your unit tests will be loaded from the out folder

This is not a good solution. For instance, you will run into problems in case your tests rely on any of those modules being initialised by the activate function (e.g. when you want to reference the extension context).

We need a way temporarily enforce loading the extension from out/extension.js for unit tests. Editing package.json every time is not a good option.

Maybe I'm just missing something, in which case please point me in the right direction.

[frenya]

This is a workaround I'm using at the moment, in case it helps anyone. It uses a global json tool to modify package.json just for the execution of unit tests. You can get it via npm install -g json

Excerpt from my package.json

{
  "scripts": {
    "test-compile": "npm run main-out && tsc -p ./",
    "main-out": "json -I -f package.json -e 'this.main=\"./out/extension.js\"'",
    "main-dist": "json -I -f package.json -e 'this.main=\"./dist/extension.js\"'"
  }
}

Excerpt from my launch.json

{
  "version": "0.2.0",
  "configurations": [{
      "name": "Extension Tests",
      "type": "extensionHost",
      "request": "launch",
      "runtimeExecutable": "${execPath}",
      "args": [
        "--extensionDevelopmentPath=${workspaceFolder}",
        "--extensionTestsPath=${workspaceFolder}/out/test/suite/index",
        "${workspaceFolder}/demo/demo.code-workspace"
      ],
      "outFiles": [
        "${workspaceFolder}/out/test/**/*.js"
      ],
      "preLaunchTask": "npm: test-compile",
      "postDebugTask": "npm: main-dist"
    }
  ]
}

[gregvanl]

Hi @frenya I've asked the VS Code engineers and I don't think there is currently a better solution than your workaround. You can see microsoft/vscode#85779 which talks about the issue and imagines a switch like --overwrite-main-field-of-package-json.

[frenya]

Thanks for the update and the link to the related issue, Greg.

[gregvanl]

@frenya Thanks for mentioning your workaround in the vscode issue to help other users.
I'll close this issue now.