TestObserver in ReactiveSwift

context("given I flag someone") {
    var testObs: TestObserver<PSSMatchViewModel.Event, Never>!
    var targetProfile: PSSProfile!

    beforeEach {
        testObs = TestObserver<PSSMatchViewModel.Event, Never>()
        viewModel.events.signal.observe(testObs.observer)

        for _ in 0..<instructionCardsNum {
            viewModel.swipe(rating: PSSMatchRating.interested)
        }

        guard case .started(let context) = viewModel.state.value else {
            XCTFail("Invalid state")
            return
        }

        guard case .profile(let profile) = context.cards.first else {
            XCTFail("Invalid state")
            return
        }

        targetProfile = profile
        viewModel.flagButtontapped()
    }

    it("then sends flagged event") {
        guard case .flagProfile(let profile) = testObs.lastValue else {
            return
        }

        expect(profile).to(equal(targetProfile))
    }
}