Module test

spy

• spy(): Spy

• Creates a new Spy instance for unit tests. A Spy is a method that takes the place of an existing method and has additional properties that can be queried to verify that certain test conditions have been met.

  example

  import * as expect from 'expect';
  import { test } from '@paychex/core';
  import someFactoryMethod from '../path/to/test/file';
  
  const { spy } = test;
  
  describe('some factory method', () => {
  
    let instance, dependency;
  
    beforeEach(() => {
      dependency = {
        methodA: spy().returns('a'),
        methodB: spy().returns('b')
      };
      instance = someFactoryMethod(dependency);
    });
  
    it('invokes dependency method a', () => {
      instance.method();
      expect(dependency.methodA.called).toBe(true);
    });
  
    it('handles error', async () => {
      const handler = spy();
      const err = new Error('test');
      dependency.methodB.throws(err);
      await instance.anotherMethod().catch(handler);
      expect(handler.called).toBe(true);
      expect(handler.args[0]).toBe(err);
    });
  
    it('retries on error', () => {
      dependency.methodA.onCall(0).throws(new Error());
      dependency.methodA.onCall(1).returns(123);
      const result = instance.method();
      expect(dependency.methodA.callCount).toBe(2);
      expect(result).toBe(123);
    });
  
  });
  

  Returns Spy

  A new Spy instance for unit testing.