Working Effectively with Legacy Code

The last consequence of avoiding change is fear

The human mind has some interesting qualities. If we have to perform a short task (5-10 seconds long) and we can only take a step once every minute, we usually do it and then pause. If we have to do some work to figure out what to do at the next step, we start to plan. After we plan, our minds wander until we can do the next step. If we compress the time between steps down from a minute to a few seconds, the quality of the mental work becomes different. We can use feedback to try out approaches quickly. Our work becomes more like driving than like waiting at a bus stop. Our concentration is more intense because we aren’t constantly waiting for the next chance to do something. Most important, the amount of time that it takes us to notice and correct mistakes is much smaller.

Remember, code is your house, and you have to live in it.

A test is not a unit test if:
1. It talks to a database.
2. It communicates across a network.
3. It touches the file system.
4. You have to do special things to your environment (such as editing configuration files) to run it.

Unit tests run fast. If they don’t run fast, they aren’t unit tests.

Here are qualities of good unit tests:
1. They run fast.
2. They help us localize problems.

legacy code is simply code without tests.

Chapter 4, The Seam Model

Chapter 4, The Seam Model

Chapter 4, The Seam Model.