jest-troubleshooting

1. TypeError: configSet.processWithEsbuild is not a function

Solution: Update jest.config.js to use jest-angular-preset instead of ts-preset.

module.exports = {
  transform: {
    '^.+\\.(ts|js|html)$': 'ts-jest', // <-- update this line
  },
};

module.exports = {
  transform: {
    '^.+\\.(ts|js|html)$': 'jest-preset-angular', // <-- update this line
  },
};

2. SyntaxError: xxx.spec.ts: Missing semicolon. (26:42)

Look into the error message, the error occurs on this line.

const compiled = fixture.nativeElement as HTMLElement;

The reason is because as, it’s a keyword in TypeScript, but it’s not a keyword in JavaScript. So the root cause is Jest cannot understand the TypeScript syntax.
We need a preset to help Jest to understand TypeScript syntax. The ts-jest is the most popular one.

• If you project is a pure TypeScript project, see here on how to config ts-jest.
• If you project is an Angular project, Please use jest-preset-angular, see here for details.

3. jest: failed to cache transform results in: xxx/jest/jest-transform-cache.map, Failure message: ENOSPC: no space left on device, write

This is because Jest is trying to transform itself, so add the following to your jest.config.js file will resolve this issue. see here for details.

transformIgnorePatterns: [
    '<rootDir>/node_modules/@babel',
    '<rootDir>/node_modules/@jest',
  ],