Medium blogpost snippet

ToggleTests.swift

func test_givenStorageThatSucceedsOnSave_whenChangingToggleValue_itEmitsUpdatedValue() {
    let mockStorage = MockToggleStorage(readValue: true, saveShouldFail: false)
    let simulatedValueSubject = PublishSubject<Bool>() // simulated user input
    let toggle = Toggle(storage: mockStorage)
    let initialValueExpectation = self.expectation(description: "will emit initial value")
    let updatedValueExpectation = self.expectation(description: "will emit 2 updated values")
    updatedValueExpectation.expectedFulfillmentCount = 2
    let (value, _) = toggle.manage(change: simulatedValueSubject.asObservable())

    var recordedValues: [ToggleValue] = []

    _ = value
        .drive(onNext: { value in
            recordedValues.append(value)
            if value.isInitial { initialValueExpectation.fulfill() }
            if value.isUpdated { updatedValueExpectation.fulfill() }
        })

    wait(for: [initialValueExpectation], timeout: 1) // wait for receiving initial value

    simulatedValueSubject.onNext(false) // then simulate user switching toggle off
    simulatedValueSubject.onNext(true) // then simulate user switching toggle on

    wait(for: [updatedValueExpectation], timeout: 1)

    XCTAssertEqual(recordedValues, [ToggleValue.initial(true), ToggleValue.updated(false), ToggleValue.updated(true)])
}