Medium blogpost snippet

TaskTests.swift

private final class MockTaskStatusDelegate: TaskStatusDelegate {

    var didCall_taskDidChangeStatus: ((Task, Task.Status) -> Void)?

    func taskDidChangeStatus(task: Task, status: Task.Status) {
        didCall_taskDidChangeStatus?(task, status)
    }
}

class TaskTests: XCTestCase {

    func test_givenTask_whenExecuted_itNotifiesDelegateAboutStatusUpdates() {
        let task = Task()
        let mockDelegate = MockTaskStatusDelegate()
        task.statusDelegate = mockDelegate

        let expectation = self.expectation(description: "delegate is called 3 times")
        expectation.expectedFulfillmentCount = 3

        var recordedStatuses: [Task.Status] = []
        mockDelegate.didCall_taskDidChangeStatus = { (_, status) in
            recordedStatuses.append(status)
            expectation.fulfill()
        }

        task.execute()

        waitForExpectations(timeout: 0.5, handler: nil)

        XCTAssertEqual(recordedStatuses, [.downloading, .processing, .finished])
    }
}