27 Iterative version upgrade strategies for large applications.md

Iterative version upgrade strategies for large applications

Writing upgradeable code

• use public APIs
  • avoid private ($$) properties
  • be suspicious of undocumented behavior
  • if you can't
    • write thorough tests
    • write abstraction layers
    • talk to the community

Write abstraction layers

• code duplication increases to upgrade
• common code allows adopting new features

Test types

Automation is key to success.

• compilation tests: TypeScript is great for this
• unit tests: Jasmine & Karma
• integration tests: Protractor
• screenshot tests

Ensuring coverage

• unit tests: Karma-coverage
• integration tests: what does this mean?
  • they log the pages touches by the integration tests
  • then compare that to the analytics (which urls the users actually hit))
• easily missed areas
  • conditional states
  • error handling

Version upgrades

Minor ones:

• update library locally
• run all test suites
• if problems are found: fix those one by one and commit those fixes one by one
• re-run all test suites (iteratively)
• release!
• adopt new features

Iterative migration strategy

• include new major library or version
• iteratively update existing features
• examples: Angular 2, Component Router, TypeScript