Screen Shot 2020-05-06 at 17 37 05

After few years working with iOS Unit-Test I conducted some tips & tricks to help to write a reliable & effectively unit-test.

Time-out should be 0.1 rather than 1 or 3

waitForExpectations(timeout: 0.1) { _ in }
wait(for: [expectation], timeout: 0.1)
  • Apple does provide this in XCTest to sever all kind of Testing: Unit-Test, Integration Test, UITest
  • Write a unit-test that depend on the timing that not a good test, will your test failed if the time-out is zero? If it failed means you’re not doing DI & Mocking well.
  • It not make your test-case passes faters, but if it’s failed, do make failed faster. This will help your CI/CD reduce a lot of time!
  • At the first glance to see a long time-out, it will make you feeling that something underneath is realy complicated.
  • 0.1 or 3 does not matter, mocking matters!
  • I have some more details on it

Not to stubbing in setUp method if not needed

  • Redundant code, some test case don’t need to use that stub, so you’re adding a un-needed implementation.
  • It won’t protect your code! Imagine that in the future your teammate make another call to existing dependency, your test won’t failed, because all is stubbed in setUp method.
  • When the test case is removed, will you/your teammate remember to remove that stub?
  • If you think it’s reusable code, then you can separate to a method, and calling that method from your test method.
  • Don’t be lazy! 💪

Always using setUp & tearDown

  • In my experiences with Unit-Test on Objective-C & Swift, using OCMock and Cuckoo, we run into a problem that when the amount of test cases reach almost 10k, your Test Target gonna be “laggy”, some test classes are leaked 😱
  • To avoid the problem above, we do add testSetUp & tearDown to clean up the memory were allocated during testing, all mocks & sut should be set to nil.
var sut: YourClass!
var yourMock: MockYour!
override func setUp() {
    sut = YourClass()
    yourMock = YourMock()
    sut.yourMock = yourMock

override func tearDown() {
    sut = nil
    yourMock = nil
func testMethod() {...}

Dispose your RxSwift subscriptions

To be safe, to not making any leak, or release immediately your memory, please do dispose your subscription!

func testFetchPartnershipProgramDetailByCode() {
    // Given:
    let expected = expectation(description: #function)

    // When:
    let subscription = sut.fetch()
        .subscribe(onNext: { _ in

    // Then:
    waitForExpectations(timeout: 0.1) { _ in

Combine with BBD - Given - When - Then

  • In my experiences that writing unit-tests take a lot of time, but when maintain someone unit-tests even take a lot of more time & effort
  • If you and you team, set some rules to make sure the anyone can understand & maintainable
func testMethodName() {
	// Given:
	/// Stubbing, mocking, preparing data for test
	// When:
	// Then:
	// Assertion places, verify

Handling Test Case Failure

Understanding Setup and Teardown for Test Methods