     }
 
     func test__add_observer_starts_notifier() {
-        try! manager.addObserver { _ in }
+        try! manager.addObserver { _ in false }
         XCTAssertTrue(manager.isRunning)
     }
 
     func test__notifier_is_only_stopped_when_last_observer_is_removed() {
-        let token1 = try! manager.addObserver { _ in }
+        let token1 = try! manager.addObserver { _ in false }
         XCTAssertTrue(manager.isRunning)
         XCTAssertTrue(network.didStartNotifier)
-        let token2 = try! manager.addObserver { _ in }
+        let token2 = try! manager.addObserver { _ in false }
         manager.removeObserverWithToken(token1)
         XCTAssertFalse(network.didStopNotifier)
         manager.removeObserverWithToken(token2)

    }

    func test__add_observer_new_observer_is_added() {
        let token = try! manager.addObserver { _ in }
        XCTAssertNotNil(manager.observersByID[token])
        XCTAssertTrue(network.didStartNotifier)
    }

    func test__remove_observer_observer_is_removed() {
        let token = try! manager.addObserver { _ in }
        manager.removeObserverWithToken(token)
        XCTAssertNil(manager.observersByID[token])
        XCTAssertTrue(network.didStopNotifier)

        manager.reachabilityForURL(NSURL(string: "invalid-host")!) { status in
            networkStatus = status
            expectation.fulfill()
            return false
        }

        waitForExpectationsWithTimeout(3, handler: nil)
