MVP-Testing-ProgressLoading.kt

    @Test
    fun `ON start fetching data IT SHOULD show progress indicator`() {
        val view: MainScreenContract.View = mockk(relaxed = true)

        val fetchCurrencyUseCase: FetchCurrencyUseCase = mockk {
            every { execute() } returns Single.never()
        }

        val presenter = MainScreenPresenter(
            fetchCurrencyUseCase = fetchCurrencyUseCase,
            schedulerProvider = TrampolineTestSchedulers()
        )

        presenter.attach(view)

        verify {
            view.toggleLoadingIndicator(true)
        }
    }

    @Test
    fun `ON fetching data complete IT SHOULD hide progress indicator`() {
        val view: MainScreenContract.View = mockk(relaxed = true)

        val fetchCurrencyUseCase: FetchCurrencyUseCase = mockk {
            every { execute() } returns Single.just(fakeCurrencyList)
        }

        val presenter = MainScreenPresenter(
            fetchCurrencyUseCase = fetchCurrencyUseCase,
            schedulerProvider = TrampolineTestSchedulers()
        )

        presenter.attach(view)

        verify {
            view.toggleLoadingIndicator(false)
        }
    }

    @Test
    fun `ON fetching data error IT SHOULD hide progress indicator`() {
        val view: MainScreenContract.View = mockk(relaxed = true)

        val fetchCurrencyUseCase: FetchCurrencyUseCase = mockk {
            every { execute() } returns Single.error(Throwable("error occurred"))
        }

        val presenter = MainScreenPresenter(
            fetchCurrencyUseCase = fetchCurrencyUseCase,
            schedulerProvider = TrampolineTestSchedulers()
        )

        presenter.attach(view)

        verify {
            view.toggleLoadingIndicator(false)
        }
    }