   expectTrue(passingTestRun.hasSucceeded)
 
   let failingTestCase = AssertEqualOptionalTestCase(selector: #selector(AssertEqualOptionalTestCase.test_whenOptionalsAreNotEqual_fails))
-  execute(failingTestCase.run)
+  let observer = FailureDescriptionObserver()
+  execute(observers: [observer], failingTestCase.run)
   let failingTestRun = failingTestCase.testRun!
   expectEqual(1, failingTestRun.testCaseCount)
   expectEqual(1, failingTestRun.executionCount)

//       instantiate an NSInvocation with the given selector.


func execute(_ run: () -> ()) {
  run()
}

XCTestTestSuite.test("exceptions") {

  expectEqual(0, failingTestRun.unexpectedExceptionCount)
  expectEqual(1, failingTestRun.totalFailureCount)
  expectFalse(failingTestRun.hasSucceeded)
  expectEqual(observer.failureDescription, "XCTAssertEqual failed: (\"Optional(1)\") is not equal to (\"Optional(2)\") - ")
}

XCTestTestSuite.test("XCTAssertEqual/Array<T>") {
