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iOS CI Infrastructure Observability

3 posts · Apr 2017 – May 2023

What this trail covers

Grab has evolved its iOS CI infrastructure by integrating observability tools to diagnose and resolve issues like unstable tests and high CPU utilization. This involved analyzing Xcode performance, optimizing deep link testing by mocking dependencies, improving simulator boot permissions, monitoring HTTP traffic, analyzing GitLab load runner performance, returning HTTP responses to a local mock server, using explicit waiting commands instead of sleep, and tracking failure states to improve test stability and reliability.

All Grab trails
  1. How we improved our iOS CI infrastructure with observability toolsThis post details specific technical improvements to the iOS CI infrastructure: 1. Reduced Xcode 13.1 CPU utilization by moving spotlight.app during tests. 2. Improved deep link testing stability and reduced CI time by creating a mock browser. 3. Booted iOS simulators with permissions to bypass runtime permission requests. 4. Developed a custom tool to monitor HTTP traffic and ensure no external resources were downloaded during UITests. 5. Enhanced a mock API tool to support HTML responses. 6. Introduced explicit waiting commands (`waitForExistence` wrappers) to replace `sleep` commands for better test stability. 7. Implemented tracking of failure states to allow merging on subsequent retries, improving engineer experience.
  2. Tackling UI Test Execution Time Imbalance for Xcode Parallel TestingThis post details a technique to overcome Xcode's parallel testing limitation where tests of the same class are grouped and run on the same simulator. By inserting a random token into the test names passed to the `-only-testing` argument of `xcodebuild`, the grouping logic is bypassed, allowing individual tests within a class to be distributed across multiple simulators. This leads to improved parallelism and reduced overall test execution time in CI pipelines.
  3. Deep Dive into iOS Automation at Grab - Integration TestingThis post details the implementation of Xcode Server for integration testing of the iOS passenger app. It covers the rationale for choosing Xcode Server over cloud services (faster integration, native environment, UI testing recording), the workflow for creating and deleting bots using Arcanist hooks, and specific 'gotchas' encountered such as simulator customization, cache issues, Xcode upgrade problems, and downtime during updates. The post also mentions the companion article on continuous delivery.