Wait for multiple async calls in setUp() of XCTestCase

Question

I need to perform multiple calls before letting the test() method run. I have a completion block, and I'm using waitForExpectations(). Since there is more than one async calls I'm using a counter. I let the expectation.fulfill() happen only when the counter reaches the number of calls.

override func setUp() {
    super.setUp()

    let exp = expectation(description: "waitForSetUp")
    var counter = 0

    // Issue an async request
    self.addEventToCalendar(title: "Test1", description: "Description test1", startDate: NSDate().addingTimeInterval(-36000), endDate: NSDate()){(success, error) in
        if (success) && (error == nil) {
            counter = counter + 1
            if(counter == 2){exp.fulfill()}
        }
    }

    self.addEventToCalendar(title: "Test2", description: "Description test2", startDate: NSDate(), endDate: NSDate().addingTimeInterval(36000)){(success, error) in
        if (success) && (error == nil) {
            counter = counter + 1
            if(counter == 2){exp.fulfill()}
        }
    }

    waitForExpectations(timeout: 40, handler: nil)        
}

This construction does not work. The test() method is sometimes run before the calls have returned (not always).

How can I make setUp() wait for returning multiple async calls?

Answer 1

I had a similar case. The solution that I end up doing was calling several functions, which add expectations for my prerequisites and setting the timeouts for the expectations to a reasonable values. In the completion handlers of the expectations I triggered the next step of my setup algorithm. After all preliminary steps pass I start the actual testing logic.

Attaching link to the Apple Docs.

EDIT: Please see the example code below :

class CommonTests: XCTestCase {
    var validate: XCTestExpectation? = nil

    func testMytest() {        
      validate(completion: {
        loadSomeStuff(completion: { (list: [Stuff]?) in
          // actual test
        }
      })
    }

    func validate(completion: @escaping ()->()) {
        self.validateExpectation = self.expectation(description: "Setup")
        // async operation can be fired here
        // or if already started from somewhere else just wait for it to complete


        self.waitForExpectations(timeout: 60) { (error: Error?) in
            XCTAssert((error == nil), error?.localizedDescription ?? "Failed with unknown error")
            completion()
        }
    }

    func validateAsyncCompleted() {
      self.validateExpectation?.fulfill()
    }

    func loadStuff(completion: @escaping ([Stuff]?)->()) {

      // possible place for assertion or some other checks

      let expectation = self.expectation(description: "loading")
      DispatchQueue.global().async {

        let result: [Stuff]? = nil
        // load operation

        expectation.fulfill()
        completion(result)
      }

      self.waitForExpectations(timeout: 90) {  (error: Error?) in
        XCTAssert((error == nil), error?.localizedDescription ?? "load - failed with unknown error")
      }
    }
}

NOTE : There are 2 approaches for the expectations, the first expectation is saved in a variable, so it can be fulfilled from another function if needed, the other is created locally in a function body and fulfilled from a closure.