jest-bug-json-transform

fixture.json

{
	"foo": 123
}

fixture.xml

<foo>
  123
</foo>

jest-test-preprocessor.js

module.exports = {
  process(src) {
    console.log('jest-test-preprocessor', src);
    return 'module.exports = ' + JSON.stringify('transformed-' + src.substr(0, 1));
  }
};

jest.test.js

const json = require('./fixture.json');
const xml = require('./fixture.xml');

describe('jest-json', function () {
  it('should transform JSON', function () {
    console.log('json', json);
    expect(json).toEqual('transformed-{');
  });

  it('should transform XML', function () {
    console.log('xml', xml);
    expect(xml).toEqual('transformed-<');
  });
});

package.json

{
  "name": "jest-test",
  "version": "1.0.0",
  "description": "",
  "scripts": {
    "test": "jest"
  },
  "license": "ISC",
  "devDependencies": {
    "jest": "^18.1.0"
  },
  "jest": {
    "verbose": true,
    "moduleFileExtensions": ["js"],
    "transform": {
      "\\.json$": "<rootDir>/jest-test-preprocessor.js",
      "\\.xml$": "<rootDir>/jest-test-preprocessor.js"
    }
  }
}

$ jest --no-cache
 FAIL  ./jest.test.js
  ● jest-json › should transform JSON

    expect(received).toEqual(expected)
    
    Expected value to equal:
      "transformed-{"
    Received:
      {"foo": 123}
    
    Difference:
    
      Comparing two different types of values. Expected string but received object.
      
      at Object.<anonymous> (jest.test.js:7:18)
      at process._tickCallback (internal/process/next_tick.js:103:7)

  jest-json
    ✕ should transform JSON (10ms)
    ✓ should transform XML (1ms)

Test Suites: 1 failed, 1 total
Tests:       1 failed, 1 passed, 2 total
Snapshots:   0 total
Time:        0.55s
Ran all test suites.
jest-test-preprocessor <foo>
  123
</foo>

  console.log jest.test.js:6
    json { foo: 123 }

  console.log jest.test.js:11
    xml transformed-<