Testing and Debugging by Michael Jurewitz (jurewitz@apple.com)

Finding and Fixing Bugs

• Unit Testing

  • Discrete pieces of code that validate behaviour
    • Verify application behaviour
    • Verify subsystems behave as designed
  • Avoids reintroducing old bugs
  • Prevents regressions
  • Core Data
    • Fully test driven from the start
    • Thousands of tests run every time its compiled
    • Allowed the team to make large changes
  • Two different types of tests
    • Logic tests
      • Run in the simulator
    • Application tests
      • Run inside the actual application on the device
  • Requires solid discipline

• Static Analysis

  • Power to find bugs you never even knew existed
  • Easy to read messages
  • Clear logical flow
  • Strengths of static analysis
    • Find bugs without test cases
    • Early detection of bugs
    • Detailed error reports
  • Analyze both iPhone and Mac apps
  • Focus areas
    • Cocoa API enforcement
    • Memory management
    • Logic errors
  • Uses Clang open source static analysis engine
  • Static = don’t run the program
  • Employs deep compiler analysis
  • Each function/method is analyzed one at a time
  • Analyzer reasons about possible execution paths
  • Program details are abstracted to achieve coverage
  • Xcode workflow should be build-analyze-fix-analyze

Using the Organizer

• Lots of features

  • Device management
  • Provisioning Profile management
  • Diagnostic data

• Summary View

  • You can download, upload application data to the sandbox on the device
  • Using the OS version dropdown, you can roll back your system version on your test device back and forth

Running Beta Tests

• Dealing with crashes

  • Get the crash log from your beta tester
  • Organizer will symbolicate crash logs for you
  • Your .app and .dSym must be locatable by Spotlight
    • Save the build files somewhere so they can be found when the crash logs come in

• Types of crashes

  • Low Memory
    • Crash log displays page count the app was using when it was jettisoned
    • Every page is 4KB
    • Mail, Phone, Safari, mediaserverd run in the background and consume memory, so it’s normal to see them in low memory logs
  • Application Errors
    • Crash log displays exception type EXC_CRASH
      • 0xdeadfa11 means low memory
      • 0x8badf00d means application became unresponsive
    • Thread that crashed is also shown below with a stack trace

• Crash reports will also be available on iTunesConnect

Fixing Crashes

• Instruments
  • Has many templates to catch specific bugs
  • Zombies template can be used to catch references to released objects

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