rejects/resolves does not fail the test on non-promise value

Do you want to request a feature or report a bug? Bug

What is the current behavior? Passing a non-promise value to rejects or resolves does not fail the test

If the current behavior is a bug, please provide the steps to reproduce and either a repl.it demo through https://repl.it/languages/jest or a minimal repository on GitHub that we can yarn install and yarn test.

Test code

describe('someMethod', () => {
  it('should reject', () => {
    expect(123).rejects.toThrow('error');
  });
});

Also this one:

describe('someMethod', () => {
  it('should reject', () => {
    const fn = new Promise((resolve, reject) => {
      resolve(1234);
    });

    expect(fn).rejects.toThrow('error');
  });
});

Output

(node:93202) UnhandledPromiseRejectionWarning: Error: expect(received).rejects.toThrow()

received value must be a Promise.
Received:
  number: 123
(node:93202) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 3)
 PASS  app/remote-control/index.spec.js
  test
    someMethod
      ✓ should reject (1ms)

  console.warn node_modules/bluebird/js/release/debuggability.js:873
    Unhandled rejection error


Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        0.226s, estimated 1s

What is the expected behavior? Should fail the test

Please provide your exact Jest configuration and mention your Jest, node, yarn/npm version and operating system. Node v9.3.0 Jest v22.1.2 Yarn v1.3.2 Mac OS X 10.12.6

[SimenB]

Note that the OP uses resolves/rejects incorrectly - it either has to be returned or awaited. See docs. If that is done, the test behaves as expected.

I still think we should give a proper synchronous error before switching into async mode, though.

There is no way for jest to detect this scenario (help welcome in the lint plugin: https://github.com/jest-community/eslint-plugin-jest/issues/54)

[github-actions[bot]]

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