Jest + Typescript + Absolute paths (baseUrl) gives error: Cannot find module

Question

I am setting a configuration to run my tests in a create-react-app + typescript app (from which I have ejected). I am using jest + enzyme. In my tsconfig.json I have set baseUrl='./src' so I can use absolute paths when I import modules. For example this is a typical import statement in one of my files:

import LayoutFlexBoxItem from 'framework/components/ui/LayoutFlexBoxItem';

You can see that the path is absolute (from /src folder) and not relative. This works fine when I run in debug mode ( yarn start )

But when I run my test ( yarn test ), I get this error:

 Cannot find module 'framework/components/Navigation' from 'index.tsx'

So it looks like jest is not able to resolve this absolute path although I have set it up in my tsconfig.json. This is my tsconfig.json:

{
  "compilerOptions": {
    "outDir": "dist",
    "module": "esnext",
    "target": "es5",
    "lib": ["es6", "dom"],
    "sourceMap": true,
    "allowJs": true,
    "jsx": "react",
    "moduleResolution": "node",
    "rootDir": "src",
    "forceConsistentCasingInFileNames": true,
    "noImplicitReturns": true,
    "noImplicitThis": true,
    "noImplicitAny": true,
    "strictNullChecks": true,
    "suppressImplicitAnyIndexErrors": true,
    "noUnusedLocals": true,
    "baseUrl": "./src"    
  },
  "exclude": [
    "node_modules",
    "build",
    "dist",
    "config",    
    "scripts",
    "acceptance-tests",
    "webpack",
    "jest",
    "src/setupTests.ts"
  ]
}

Now I can see that there is a generated tsconfig.test.json at the root of my project. This is the ts configuration used for test. And here is its content:

{
  "extends": "./tsconfig.json",
  "compilerOptions": {
    "module": "commonjs"
  }
}

As you can see the "module" is commonjs here whereas in the default configuration it is esnext. Could this be one reason?

Has any one been able to unit test his typescript project with Jest and absolute path? or is this a known bug? Since I have ejected from default configuration, are there some settings to put in my webpack configuration?

Thanks for your input and suggestion.

Answer 1

I was struggling with the same problem and actually it turns out that a simple change seems to do the trick.

I just updated the moduleDirectories field in jest.config.js.

Before

moduleDirectories: ['node_modules']

After

moduleDirectories: ['node_modules', 'src']

Hope it helps.

Answer 2

As many here pointed out moduleNameMapper in jest.config.js needs to define paths specified in tsconfig.json. For example, if you have paths in tsconfig.json defined as follows

// tsconfig.json
{
 ...
 "baseUrl": "src",
 "paths": {
    "@alias/*": [ 'path/to/alias/*' ]
 }
 ...
}

then your jest.config.js needs to provide those paths in moduleNameMapper in the following format:

// jest.config.js
module.exports = {
    'roots': [
        '<rootDir>/src'
    ],
    'transform': {
        '^.+\\.tsx?$': 'ts-jest'
    },
    'moduleNameMapper': {
         '@alias/(.*)': '<rootDir>/src/path/to/alias/$1'
    }
};

Having that we can improve our jest.config.js to convert paths defined in tsconfig.json automatically. Here is a Gist code snippet for that:

// jest.config.js

function makeModuleNameMapper(srcPath, tsconfigPath) {
    // Get paths from tsconfig
    const {paths} = require(tsconfigPath).compilerOptions;

    const aliases = {};

    // Iterate over paths and convert them into moduleNameMapper format
    Object.keys(paths).forEach((item) => {
        const key = item.replace('/*', '/(.*)');
        const path = paths[item][0].replace('/*', '/$1');
        aliases[key] = srcPath + '/' + path;
    });
    return aliases;
}

const TS_CONFIG_PATH = './tsconfig.json';
const SRC_PATH = '<rootDir>/src';

module.exports = {
    'roots': [
        SRC_PATH
    ],
    'transform': {
        '^.+\\.tsx?$': 'ts-jest'
    },
    'moduleNameMapper': makeModuleNameMapper(SRC_PATH, TS_CONFIG_PATH)
};

Answer 3

Here is how I got moduleNameMapper working.

With the below config in my tsconfig:

    "paths": {
      "@App/*": [
        "src/*"
      ],
      "@Shared/*": [
        "src/Shared/*"
      ]
    },

Here's the moduleNameMapper:

"moduleNameMapper": {
  "@App/(.*)": "<rootDir>/src/$1",
  "@Shared/(.*)": "<rootDir>/src/Shared/$1"
}

Answer 4

Add this following section in your package.json. after you made the changes don't forget to restart your test watchers.

  "jest": {
    "moduleDirectories": [
      "node_modules",
      "src"
    ],
    "moduleFileExtensions": [
      "js",
      "json",
      "ts"
    ],
    "roots": [
      "src"
    ],
    "testRegex": ".spec.ts$",
    "transform": {
      "^.+\\.(t|j)s$": "ts-jest"
    },
    "coverageDirectory": "../coverage",
    "testEnvironment": "node",
    "moduleNameMapper": {
      "src/(.*)": "<rootDir>/src/$1"
    }
  }