when called

  • <function> [when] called <assertion?>

Call the subject function without arguments, then delegate the return value to another assertion.

function giveMeFive() {
    return 5;
}
 
expect(giveMeFive, 'when called', 'to equal', 5);

In case of a failing expectation you get the following output:

expect(giveMeFive, 'when called', 'to equal', 7);
expected function giveMeFive() { return 5; } when called to equal 7
  
expected 5 to equal 7

If you don't provide an assertion to delegate to, the return value will be provided as the fulfillment value of the promise:

return expect(giveMeFive, 'called').then(function (result) {
    expect(result, 'to equal', 5);
});