Journey to TDD - Legacy System Puzzle

If you found this article and want to start at the beginning, this series starts here.

Tracking smoke tests will become unscalable.

With a “legacy system”, one where you do not have tests, the best and the option I always recommend:

Write tests.

Testing an “untested system” is rough - because it’s a big black box. You don’t know anything about that box. What should go in? What should come out? When things go in, what should come out?

Legacy systems are a giant puzzle and the best way to solve legacy system puzzles is to test from what you know of the system.

• Poke
• Prod
• Record
• Repeat

Once there’s a bit of understanding - write tests! Even at a high level, this will help you.

How much will this help?

If there were ZERO tests, adding ONE test helps you 1,000,000x!