TestingCancelAssertTasksCount2.swift

func test_cancellAllTasks_givenExistsActiveTasks_shouldCancellAllOfThem() {
  ...

  let cancelTasksExpectation = XCTestExpectation(description: "cancelTasksExpectation")
        
  DispatchQueue.main.asyncAfter(deadline: .now() + 0.1) {
    sut.session.getAllTasks { tasks in
      activeTasksCount = tasks.count
      cancelTasksExpectation.fulfill()
    }
  }
  
  wait(for: [cancelTasksExpectation], timeout: 0.2)
        
  XCTAssertEqual(activeTasksCount, 0)
}