1. example-test.js

describe('Example', function () {
  it('should fail when extra undefined keys are passed', function() {
    var test = jest.genMockFunction();
    test({a: 1, b: undefined});
    expect(test).toBeCalledWith({a: 1});
  });
});

2. Actual

$ jest
Using Jest CLI v0.2.1
 PASS  __tests__/example-test.js (0.018s)
1 test passed (1 total)
Run time: 0.417s

3. Expected

$ jest
Using Jest CLI v0.2.1
 FAIL  __tests__/example-test.js (0.03s)
● Example › it should fail when extra undefined keys are passed
  - Expected: {
    | 0: {
    | | a: 1,
    | | b: undefined
    | }
    } toEqual: {
    | 0: {
    | | a: 1
    | }
    }
        at addMatchers.toBeCalledWith (/usr/lib/node_modules/jest-cli/src/jasmineTestRunner/jasmineTestRunner.js:217:18)
        at Spec.<anonymous> (/home/user/tmp/test/__tests__/example-test.js:5:18)
        at Timer.listOnTimeout [as ontimeout] (timers.js:110:15)
1 test failed, 0 tests passed (1 total)
Run time: 0.424s