Continuous Integration

Overview

Teaching: 5 min
Exercises: 10 min

Questions

• How can I tell what state my project is actually in?

Objectives

• Explain how continuous integration works.

• Configure continuous integration for a small software project.

• Continuous integration:
  • Build and test code every time someone commits code
  • Post results somewhere the team can see them
  • If build or tests fail, send out notifications
• Even better: build and test changes before they’re merged
  • Only do code review on changes that have passed mechanical checks
• Keep track of test coverage
  • Which parts of the code are being exercised and which aren’t
  • Many different ways to measure
  • Most important measurement is “are we holding steady?”
• Most widely used system is Travis CI
  • Easy integration with Github
  • Will run tests on multiple platforms and with multiple versions of tools
• Developers still have to build the tests
  • CI only as good as the tests it runs
• Check style as well as correctness
  • Sometimes called “linters” after the original lint for C
  • Equivalents have been built for most languages
    • pep8 for Python
    • formatR for R
  • Most are configurable
    • Stick to a pre-defined style rather than argue about one of your own
  • Automatic enforcement eliminates subjective arguments
    • If the linter passes, the code is approved
    • Guarantees you never have to worry about style if the linter is happy
    • Most linters support exceptions, these can be approved in code review on a case-by-case basis

Lint Your Code

1. Find and install a lint-like tool for your preferred language and run it on your code.
2. What does it complain about?
3. Which of its complaints do you disagree with?

Setting Up Continuous Integration

Follow the steps in this tutorial to set up Travis-CI testing for the SNDS repository. How long did it take you to set this up?

Key Points

• Continuous integration rebuilds and/or re-tests software every time something changes.

• Use continuous integration to check changes before they are inspected.

• Check style as well as correctness.

• Adopt a widely-used pre-defined coding style rather than inventing one of your own.