Parameterized test helper for Jest

setup-parameterized-tests.js

/**
 * Setup parameterized tests for a dictionary of inputs and outputs.
 * This allows you to run tests over a list of inputs and outputs,
 * without much setup. For example:
 *
 *   setupParameterizedTests(x => getFirstName(x))([
 *     ['John M. Smith',  'John'],
 *     ['Joe Schmoe Jr.', 'Joe']
 *   ]);
 *
 * Each case will call `expect().toEqual()` for you, but provide enough
 * information that test case failures are debuggable using test output.
 *
 * @param {Function} fn - function to run on input, which produces output
 * @param {Array} dictionary - 2D array containing pairs of input/output
 */
export default function setupParameterizedTests(fn) {
  return dictionary => {
    dictionary.forEach(([input, result]) => {
      expect({input, result: fn(input)}).toEqual({input, result});
    });
  };
}