cosmiconfig - Sample migration to jest

jest-report.md

 PASS  test\successful-files.test.js
  cosmiconfig.load
    sync
      √ loads defined JSON config path (4ms)
      √ loads defined YAML config path (1ms)
      √ loads defined JS config path (2ms)
      √ loads modularized JS file (2ms)
      √ runs transform (5ms)
      √ does not swallow transform errors (1ms)
    async
      √ loads defined JSON config path (4ms)
      √ loads defined YAML config path (2ms)
      √ loads defined JS config path (2ms)
      √ loads modularized JS file (3ms)
      √ runs transform (2ms)
      √ does not swallow transform errors (1ms)

Test Suites: 1 passed, 1 total
Tests:       12 passed, 12 total
Snapshots:   0 total
Time:        0.27s, estimated 1s
Ran all test suites matching /success/.

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test\successful-files.test.js

'use strict';

const util = require('./util');

const absolutePath = util.absolutePath;
const configFileLoader = util.configFileLoader;
const testResolves = util.testResolves;
const testRejects = util.testRejects;

describe('cosmiconfig.load', () => {
  const expectRes = file => result => {
    expect(result.config).toEqual({
      foo: true,
    });
    expect(result.filepath).toBe(absolutePath(file));
  };
  ['json', 'yaml', 'js'].forEach(format => {
    const file = `fixtures/foo.${format}`;
    testResolves(
      `loads defined ${format.toUpperCase()} config path`,
      configFileLoader,
      [file],
      expectRes(file)
    );
  });

  testResolves(
    'loads modularized JS file',
    configFileLoader,
    ['fixtures/foo-module.js'],
    expectRes('fixtures/foo-module.js')
  );

  // for testing transform, it should be enough to check for any 1 file type
  testResolves(
    'runs transform',
    configFileLoader,
    [
      'fixtures/foo.json',
      {
        transform(result) {
          result.config.foo = [result.config.foo];
          return result;
        },
      },
    ],
    result => expect(result.config).toEqual({ foo: [true] })
  );

  testRejects(
    'does not swallow transform errors',
    configFileLoader,
    [
      'fixtures/foo.json',
      {
        transform() {
          throw new Error('These pretzels are making me thirsty!');
        },
      },
    ],
    err => {
      expect(err.message).toBe('These pretzels are making me thirsty!');
    }
  );
});

test\util.js

'use strict';

const path = require('path');
const isPromise = require('is-promise');
const cosmiconfig = require('..');

function absolutePath(str) {
  return path.join(__dirname, str);
}

exports.absolutePath = absolutePath;

exports.configFileLoader = function configFileLoader(sync, file, options) {
  const mergedOptions = Object.assign({ sync }, options);
  const loadConfig = cosmiconfig(null, mergedOptions).load;
  return loadConfig(null, absolutePath(file));
};

exports.testResolves = function testResolves(name, testFn, args, checkFn) {
  describe('sync', () => {
    it(name, () => {
      checkFn(testFn.apply(null, [true].concat(args)));
    });
  });

  describe('async', () => {
    it(name, () => {
      return testFn.apply(null, [false].concat(args)).then(checkFn);
    });
  });
};

exports.testRejects = function testRejects(name, throwFn, args, checkFn) {
  describe('sync', () => {
    it(name, () => {
      expect.hasAssertions();
      try {
        throwFn.apply(null, [true].concat(args));
      } catch (err) {
        checkFn(err);
      }
    });
  });

  describe('async', () => {
    it(name, () => {
      expect.hasAssertions();
      return throwFn.apply(null, [false].concat(args)).catch(checkFn);
    });
  });
};