After adding a new feature to the iOS app I currently works on I noticed an unexpected memory spike after the app was used for a while. This usually means a memory leak; some object not being deallocated after it is no longed need. This is often caused by using self without unowned / weak or by forgetting to make the delegates weak (tools like SwiftLint can warn you about this case).
In my case the problem was a UIViewController not being deallocated after being removed from the navigation stuck because of a error in a binding. I found the bug using the Instruments in Xcode but it got me ask some questions. What if there are memory leaks in other parts for the app, in flows that are not used so much? Is there a way to somehow automatically test for memory leaks? I found SpecLeaks as the best way to answer those questions.
SpecLeaks
SpecLeaks is a framework build on top of Quick and Nimble that helps you to unit test memory leaks in Swift. You can use it to unit test memory leaks in any kind of objects, I chose to unit test my view controllers because they seemed to be most probable cause of memory leaks in my apps.
SpecLeaks can detect that your are testing a UIViewController and also call viewDidLoad to fully initialize the UIViewController. A simple memory leak test may then look like this
class SomeViewControllerTests: QuickSpec {
override func spec() {
describe("SomeViewController") {
describe("viewDidLoad") {
let vc = LeakTest {
return SomeViewController()
}
it("must not leak"){
expect(vc).toNot(leak())
}
}
}
}
}You can initialize your view controllers using init or get them from story boards, it does not matter. The unit tests will fail for every leaking view UIViewController.
