Cannot find module spdx-license-ids from .../spdx-expression-parse/scan.js

Error

Test server › should return OK on /health

    Cannot find module 'spdx-license-ids' from '../../node_modules/spdx-expression-parse/scan.js'

    Require stack:
      /Users/duc.nguyen/Workspace/sample-project/node_modules/spdx-expression-parse/scan.js
      /Users/duc.nguyen/Workspace/sample-project/node_modules/spdx-expression-parse/index.js
      /Users/duc.nguyen/Workspace/sample-project/node_modules/validate-npm-package-license/index.js
      /Users/duc.nguyen/Workspace/sample-project/node_modules/normalize-package-data/lib/fixer.js
      /Users/duc.nguyen/Workspace/sample-project/node_modules/normalize-package-data/lib/normalize.js
      /Users/duc.nguyen/Workspace/sample-project/node_modules/read-pkg-up/node_modules/read-pkg/index.js
      /Users/duc.nguyen/Workspace/sample-project/node_modules/read-pkg-up/index.js
      /Users/duc.nguyen/Workspace/sample-project/node_modules/koa2-swagger-ui/dist/index.js
      src/server.ts
      src/server.test.ts

      at Resolver.resolveModule (../../node_modules/jest-resolve/build/resolver.js:311:11)
      at Object.<anonymous> (../../node_modules/spdx-expression-parse/scan.js:4:11)

How to fix

Current jest.config.json

module.exports = {
	//...rest
	moduleFileExtensions: ["ts", "js", "html"],
};

We will need to add json

module.exports = {
	//...rest
	moduleFileExtensions: ["ts", "js", "html", "json"],
};

Reason

The package that failed this time is spdx-license-ids, but the json file is used internally. jest will only read files with the extension specified in moduleFileExtensions in config. So It couldn’t read the json file used by spdx-license-ids and got an error.

By the way, the initial value of moduleFileExtensions of jest is

["js", "json", "jsx", "ts", "tsx", "node"]

So this error wouldn’t have happened if I hadn’t made any extra settings 😇

Source: https://qiita.com/nekoshita_yuki/items/b20b76cad37a6c9748b8