how_unit_testing_can_help_write_better_designs_9.swift

final class MovieManagerTests: XCTestCase {

    private var storeSpy: KeyValueStoreSpy!

    private var clientSpy: ClientSpy!

    private var movieManager: MovieManaging!

    override func setUp() {
        super.setUp()

        storeSpy = KeyValueStoreSpy()
        clientSpy = ClientSpy()
        movieManager = MovieManager(client: clientSpy, store: storeSpy)
    }

    override func tearDown() {
        defer { super.tearDown() }

        storeSpy = nil
        clientSpy = nil
        movieManager = nil
    }

    // MARK: - getPopularMovies(_:)

    func test_getPopularMovies_should_get_a_list_of_movies_from_the_server() {

        let expectedMovies = [Movie(...), Movie(...)]
        clientSpy.getResultStub["/movies/popular"] = Result<[Movie], MovieManagerError>.success(expectedMovies)

        let expectation = self.expectation(description: "get_movies")
        movieManagerSpy.getPopularMovies { result in

            switch result {
            case .success(let movies):
                XCTAssertEqual(movies, expectedMovies)
                XCTAssertEqual(clientSpy.pathRecords.first, "/movies/popular")
                XCTAssertEqual(clientSpy.pathRecords.count, 1)

            case .failure(let error):
                XCTFailure("Unexpected error: \(error)")
            }

            expectation.fulfill()
        }

        wait(for: [expectation], timeout: 1)
    }

    func test_getPopularMovies_should_cache_two_movies() {

        let expectedMovies = [Movie(...), Movie(...)]
        clientSpy.getResultStub["/movies/popular"] = Result<[Movie], MovieManagerError>.success(expectedMovies)

        let expectation = self.expectation(description: "get_movies")
        movieManagerSpy.getPopularMovies { result in

            switch result {
            case .success(let movies):
                var storeSpyKeyRecords = storeSpy.keyRecords
                XCTAssertEqual(storeSpyKeyRecords.removeFirst(), expectedMovies[0].id)
                XCTAssertEqual(storeSpyKeyRecords.removeFirst(), expectedMovies[1].id)
                XCTAssertEqual(storeSpy.keyRecords.count, 2)
                XCTAssertEqual(movie, expectedMovie)

            case .failure(let error):
                XCTFailure("Unexpected error: \(error)")
            }

            expectation.fulfill()
        }

        wait(for: [expectation], timeout: 1)   
    }

    // MARK: - getMovie(id:completion:)

    func test_getMovie_should_get_a_movie_from_store() {

        let expectedMovie = Movie(id: "42", ...)
        storeSpy.getEntryResultStub["42"] = expectedMovie

        let expectation = self.expectation(description: "get_movie")
        movieManagerSpy.getMovie(id: "42") { result in
            switch result {
            case .success(let movie):
                XCTAssertEqual(storeSpy.keyRecords.count, 1)
                XCTAssertEqual(storeSpy.keyRecords.first, "42")
                XCTAssertEqual(storeSpy.valueRecords.count, 0)
                XCTAssertEqual(clientSpy.pathRecords.count, 0)
                XCTAssertEqual(movie, expectedMovie)

            case .failure(let error):
                XCTFailure("Unexpected error: \(error)")
            }
        }
    }

    func test_getMovie_should_get_a_movie_from_server() {

        let expectedMovie = Movie(id: "42", ...)
        clientSpy.getResultStub["/movies/42"] = Result<Movie, MovieManagerError>.success(expectedMovie)

        let expectation = self.expectation(description: "get_movie")
        movieManagerSpy.getMovie(id: "42") { result in
            switch result {
            case .success(let movie):
                XCTAssertEqual(clientSpy.pathRecords.first, "/movies/42")
                XCTAssertEqual(clientSpy.pathRecords.count, 1)
                XCTAssertEqual(movie, expectedMovie)

            case .failure(let error):
                XCTFailure("Unexpected error: \(error)")
            }
        }
    }

    func test_getMovie_should_get_a_movie_from_server_and_store_it() {

        let expectedMovie = Movie(id: "42", ...)
        clientSpy.getResultStub["/movies/42"] = Result<Movie, MovieManagerError>.success(expectedMovie)

        let expectation = self.expectation(description: "get_movie")
        movieManagerSpy.getMovie(id: "42") { result in
            switch result {
            case .success(let movie):
                XCTAssertEqual(storeSpy.valueRecords.count, 1)
                XCTAssertEqual(storeSpy.valueRecords.first as? Movie, expectedMovie)
                XCTAssertEqual(storeSpy.keyRecords.count, 1)
                XCTAssertEqual(storeSpy.keyRecords.first, "42")

            case .failure(let error):
                XCTFailure("Unexpected error: \(error)")
            }
        }
    }
}