Tutorial

This tutorial will walk you through Test Driven Development using Testix and pytest.

We will develop a small project in this tutorial, test driven of course, which solves the following real-life problem: suppose you want to run some subprocess, and you want to read its output line-by-line in real time and take appropriate action.

An example application might be that you want to monitor live logs and do something whenever a log line has ERROR in it.

Let’s call this library LineMonitor.

• Design of the LineMonitor
  • Unit Tests
  • Integration Tests
  • End-to-End (E2E) Tests
• End-to-End Test
  • Tests Driving our Code
• Failing Properly
  • The Importance of Proper Failure
• Testix Basics
  • Working With Scenarios and Fake Objects
    • Mock Objects
    • The Standard Library Way - unittest.mock
    • Testix Fake Objects and Scenarios
      • Setting the Expectations
      • Meeting the Expectations
  • More Advanced Tests
    • Specifying Return Values
    • Exactness
  • Exact Enforcement
    • Wrong Arguments
    • Unexpected Calls
    • Ways Around Exactness
  • Recap
• Line Monitor Unit Tests
  • Launching the Subprocess
    • High Level Design
    • Implementation
      • Failing the Test
      • Passing the Test
  • Monitoring The Output
    • Edge Case Test: When There is no Callback
    • Edge Case Test: Asynchronous Callback Registration
    • Let’s Recap
  • Recap
    • YAGNI
    • Code Recap
  • Watching The Subprocess
    • Polling the Read File Descriptor
    • Solving the Blocking Problem
      • Oops, a bug
    • Has the Subprocess Died?
• Conclusion
• More About Readability