times = [new DateTimeImmutable(), new DateTimeImmutable()]; }); test('pass', function () { expect($this->times)->toContainOnlyInstancesOf(DateTimeImmutable::class); expect($this->times)->not->toContainOnlyInstancesOf(DateTime::class); }); test('failures', function () { expect($this->times)->toContainOnlyInstancesOf(DateTime::class); })->throws(ExpectationFailedException::class); test('not failures', function () { expect($this->times)->not->toContainOnlyInstancesOf(DateTimeImmutable::class); })->throws(ExpectationFailedException::class);