Medium blogpost snippet

LevelSelectionViewModelTests.swift

class LevelSelectionViewModelTests: XCTestCase {

    private var viewModel: LevelSelectionViewModel!
    private var mockDelegate: MockLevelSelectionViewModelDelegate!

    override func setUp() {
        super.setUp()
        let levels = [
            Level(status: .unlocked, identifier: "abc"),
            Level(status: .locked, identifier: "def")
        ]
        viewModel = LevelSelectionViewModel(levels: levels)
        mockDelegate = MockLevelSelectionViewModelDelegate()
        viewModel.delegate = mockDelegate
    }

    override func tearDown() {
        super.tearDown()
        viewModel = nil
        mockDelegate = nil
    }

    func test_whenSelectingUnlockedLevel_itNotifiesDelegate() {
        let expectation = self.expectation(description: "delegate is called")

        mockDelegate.didCall_didRequestOpeningLevelWithIdentifier = { identifier in
            XCTAssertEqual(identifier, "abc")
            expectation.fulfill()
        }

        viewModel.selectLevel(atIndex: 0) // simulate user input

        waitForExpectations(timeout: 0.5, handler: nil)
    }

    func test_whenSelectingLockedLevel_itDoesNotNotifyDelegate() {
        let expectation = self.expectation(description: "delegate is not called")
        expectation.isInverted = true

        mockDelegate.didCall_didRequestOpeningLevelWithIdentifier = { identifier in
            expectation.fulfill()
        }

        viewModel.selectLevel(atIndex: 1) // simulate user input

        waitForExpectations(timeout: 0.5, handler: nil)
    }
}