Quality Code: Software Testing Principles, Practices, and Patterns

Use Supervisory Control

Sometimes, when you are testing, you just cannot find a seam. Maybe a class is too well encapsulated. Perhaps the designer of the software under test did not recognize a need to allow the calling code to insert behavioral or monitoring hooks into the software. Maybe the software is already highly synchronized to a point at which it “couldn’t possibly have a race condition,” at least until the ongoing evolution of the system changes the assumptions under which it was originally thread-safe.

The latter happened in a system I worked with at one time. Imagine a system in which autonomous agents¹⁰ collaborate in a manner governed by a tightly designed state machine to collectively achieve the application goal. In this particular ...