Unit Test HKSampleQuery in Swift

When I need to read data from HealthKit this is how my code looks like:

let stepsCount = HKQuantityType.quantityTypeForIdentifier(HKQuantityTypeIdentifierStepCount)

let stepsSampleQuery = HKSampleQuery(sampleType: stepsCount,
    predicate: nil,
    limit: 100,
    sortDescriptors: nil)
    { [unowned self] (query, results, error) in
        if let results = results as? [HKQuantitySample] {
            self.steps = results
            // Update some UI
        }
        self.activityIndicator.stopAnimating()
}

healthStore?.executeQuery(stepsSampleQuery)

This specific code was extracted from here for demo purpose.

So my question is:

How can I unit test this kind of code ?

I encapsulate this code in a function in a model class that knows nothing about the UI. It works like this:

At the place the you have your

// Update some UI

call a completion closure, that was passed to the function using a parameter.

You call this function from your controller class like this

hkModel.selectSteps() {
    [unowned self] (query, results, error) in
    // update UI
}

This way you have a clean separation between your query logic in the model class and your UIController code.

Now you can easily write a unit test calling the same method:

func testSteps() {
    hkModel.selectSteps() {
        [unowned self] (query, results, error) in
        // XCTAssert(...)
    }
}

The last thing you need is to respect that your test code is called asynchronously:

let stepExpectationEnd = expectationWithDescription("step Query")
hkModel.selectSteps() {
    [unowned self] (query, results, error) in
    // XCTAssert(...)
    stepExpectationEnd.fulfill()
}
waitForExpectationsWithTimeout(10.0) {
    (error: NSError?) in
     if let error = error {
         XCTFail(error.localizedDescription)
     }
}

update

Because you asked:

I handle authorization at the test setup. looks like this:

var healthData: HealthDataManager?
override func setUp() {
    super.setUp()
    healthData = HealthDataManager()
    XCTAssert(healthData != nil, "healthDadta must be there")

    let authorizationAndAScheduleExpectation = expectationWithDescription("Wait for authorizatiion. Might be manual the first time")
    healthData?.authorizeHealthKit({ (success: Bool, error: NSError?) -> Void in
        print ("success: \(success) error \(error?.localizedDescription)")
        // fails on iPad
        XCTAssert(success, "authorization error \(error?.localizedDescription)")

        self.healthData?.scheduleAll() {
            (success:Bool, error:ErrorType?) -> Void in
            XCTAssert(success, "scheduleAll error \(error)")

            authorizationAndAScheduleExpectation.fulfill()
        }
    })
    waitForExpectationsWithTimeout(60.0) {
        error in
        if let error = error {
            XCTFail(error.localizedDescription)
        }
    }
}

The first time you run this code in a simulator, you have to approve authorization manually.

After the first run the tests run without manual intervention.