Testing and troubleshooting your app
Now that you have learned about performance bottlenecks and some of the ways to mitigate them this unit will discuss testing techniques. These techniques are a combination of guidance, techniques, and discovery that apply both to performance testing and general debugging.
Using the Timer control to get metrics
When it comes to working with data connections for retrieving or uploading data, hard numbers are helpful. In Power Apps, you can use a variable and a Timer control to capture how long your formula takes to run. The following scenario will show you how.
Assume you have a Button with the OnSelect property set to the following:
Collect(collectDepartmentList, Filter(DepartmentList, Status = "Active"))
- Modify that formula to the following to add a variable that you will use to Start and Stop the timer.
Reset(Timer1);Set(varTimerStart, true);Refresh(collectDepartmentList); ClearCollect(collectDepartmentList, Filter(DepartmentList, Status = "Active"));Set(varTimerStart, false)
You will see an error about Timer1 because you have not added it to the app yet. You can ignore the error until you complete the next step.
To capture exactly how long that formula takes, you will need to first add a Timer control to your app and make sure that it is named Timer1. The Timer control is on the Insert menu under Input.
For the Timer control, set the Start property to the following: varTimerStart.
Now insert a Label control to display the time.
For the Text property of the Label control set the formula to the following: Timer1.Value
Now preview the app and click the Button.
In your label, you will see how long your collection takes to create in milliseconds.
This works well for when you want to understand exactly how long a specific query is taking. You could log this data to a different collection and then average the numbers to determine how long it takes. You can also apply this concept to submitting data. Remember to test not only from your local computer but from all of the scenarios for your user's environments.
Test where your users will use the app
This is more advice than technique. For most app builders the best place to run an app is from the local PC they use to build the app. Testing from that machine generally gives the best case results but may not match your user's experience. Far too often they forget to test the way the user will run the app. For example, if you are going to build a mobile app that runs over a cellular network then make sure your testing includes the same. Understanding the smaller form factor of the mobile device and the latency of a varying internet connection needs to factor into your app's design. The previous timer testing method is great here. Compare the app's query or upload performance between your PC, your mobile phone on Wi-Fi, and your mobile phone on cellular data. Determine if you are satisfied with all three scenarios or if you need to optimize your app for the slower network.
Use labels to help with testing
As your app incorporates more complex logic and more behind the scenes variables to facilitate that logic consider using label controls as part of your testing toolkit. Simply adding a label to the screen that displays the value of the variable can go a long way to helping you understand why your app is or is not doing something. You can use this during the building and testing phase. When your app is live, you can add additional functionality for hiding and showing these troubleshooting tools.
While you are in the Power Apps Studio you can also select File and Variables to see all of your variables, their values, where they were created, and where they are used in the app.
Another way to use labels during the build process is to add a label to the welcome screen where you manually display a version number. Power Apps caches your app to optimize your experience. When you are publishing repetitively, like when customizing a SharePoint form, it can be confusing to know which version of the form you are seeing as you may see a cached version. By simply adding a label with v1 or v2 in the corner, you will always be able to check the version.
Preview versus Published apps
Using the preview capability of the Power Apps Studio gives you great insight into how your app will run when you publish it. But sometimes you may find some inconsistency due to cache or other things your local PC is doing versus what the published app will do in the player. Always remember to test your app after published, in a manner that is consistent with how the user will use the app.
Looking at the network activity of your app
Now that you have learned about testing from within the app you need to look at actual network calls and performance. To do this you can use your browsers built-in developer tools, Ctrl+Shift+I in Chrome or F12 in Edge/IE, or a third-party tool like Fiddler. This will allow you to view the individual network calls made by your app and view details, such as time that each call takes. From a performance point of view, this can be valuable.
One example of a way you can use this is to determine if performance slowness, as measured by the Timer control from the previous example, is within your app, the network, or the data source. By using the Developer Tools in Microsoft Edge, you can see the breakdown of the query that took 1.55 seconds in Power Apps.
By hovering over the query in the bottom right of the screen, you can see the time breakdown as follows.
In this instance, most of the time was spent waiting on the data source to filter the data and respond. This tells you that you cannot make the call faster by changing the app. Instead, you would need to focus on refining the query or speeding up the data source.
This level of information can be overwhelming at first but don't try to learn the whole interface of the developer tools, instead, concentrate on just the pieces you need like the network timelines.
Additionally, you can use the developer tools to get more details about error messages returned in the app or a stronger indication where connectivity issues are occurring.