NEW! Check out my latest book, Testing Swift! >>

How to set baselines for your performance tests

Paul Hudson       @twostraws

All performance tests in Xcode can have baselines attached to them, which are stored results that you consider representative of your app’s performance as things stand. The baseline is useful because it gives Xcode a measuring point for all other changes you make: if you accidentally change your code so that it runs slower, Xcode will consider your performance test to be a failure.

To set a baseline for a performance test, first make sure it has been run at least once. You should see a gray bar next to the test saying “No baseline average for time”, but if you click the gray diamond to the left of your test a balloon appears offering more information.

To set a baseline, click the Set Baseline button inside that balloon. You’ll see a “Max STDDEV” field set to 10% by default – that’s how much variance Xcode allows before it considers a test to have failed, but you can change it however you want. Broadly speaking, extremely fast code should have a higher standard deviation allowance than slower code, only because extremely fast code is likely to show more variance due to system conditions.

Available from iOS

Did this solution work for you? Please pass it on!

Other people are reading…

About the Swift Knowledge Base

This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.

Need to know Objective-C fast?

I wrote a book dedicated to teaching Objective-C to developers who already know Swift – it's the fastest way to get up to speed!

MASTER SWIFT NOW
Buy Testing Swift Buy Practical iOS 12 Buy Pro Swift Buy Swift Design Patterns Buy Swift Coding Challenges Buy Server-Side Swift (Vapor Edition) Buy Server-Side Swift (Kitura Edition) Buy Hacking with macOS Buy Advanced iOS Volume One Buy Advanced iOS Volume Two Buy Hacking with watchOS Buy Hacking with tvOS Buy Hacking with Swift Buy Dive Into SpriteKit Buy Swift in Sixty Seconds Buy Objective-C for Swift Developers Buy Beyond Code

Was this page useful? Let me know!

Click here to visit the Hacking with Swift store >>