Test- Driven Development

We know from decades of experience that Test-Driven Development (TDD) will help you developer better quality code, faster.

If your teams are suffering from any of these problems, TDD will help:

• Regressions found in production after launch
• Delayed releases due to last minute defects
• Gradually slowing velocity
• Growing areas of the code considered 'no-mans-land' - too dangerous to touch or change

Test-Driven Development (TDD) is an incremental and iterative approach to developing software that follows a simple 3-step cycle:

1. Write a failing test (RED)
2. Make it pass (GREEN)
3. Refactor

This simple practice has a huge impact on the kinds of issues listed above. The means by which this happen are numerous, but include:

• Catching regressions as soon as they are introduced means less time spent resolving them:
  • The knowledge of how to resolve it is fresh, and the cause is obvious - it must be the code introduced in the last few minutes. (Compare with the experience of discovering the defect weeks later in manual testing).
• Small increments reduce the cognitive load in each cycle, reducing risk of introducing defects
• You are discouraged from adding code/features that aren't needed yet
  • These are a common cause of the most tragic defects - releases held up due to bugs caused by functionality added 'just in case', that nobody really needs yet!
• Frequent refactoring makes future changes easier
  • The cost of refactoring rises exponentially as the code accumulates cruft. Frequently clearing out the cruft, which is enabled by the high test coverages, keeps that cost low.
• Valuable practices like continuous delivery are enabled because the code is always in a releasable state

This course takes an experiential training approach - there is a limited amount of slides/theory, most of the time is either spent watching live demos or doing active practical work in teams.