Much like we gain knowledge about the behavior of the physical universe via the scientific method, we gain knowledge about the behavior of our software via a system of assertion, observation, and experimentation called “testing.”
There are many things one could desire to know about a software system. It seems that most often we want to know if it actually behaves like we intended it to behave. That is, we wrote some code with a particular intention in mind, does it actually do that when we run it?
In a sense, testing software is the reverse of the traditional scientific method, where you test the universe and then use the results of that experiment to refine your hypothesis. Instead, with software, if our “experiments” (tests) don’t prove out our hypothesis (the assertions the test is making), we change the system we are testing. That is, if a test fails, it hopefully means that our software needs to be changed, not that our test needs to be changed. Sometimes we do also need to change our tests in order to properly reflect the current state of our software, though. It can seem like a frustrating and useless waste of time to do such test adjustment, but in reality it’s a natural part of this two-way scientific method–sometimes we’re learning that our tests are wrong, and sometimes our tests are telling us that our system is out of whack and needs to be repaired.
This tells us a few things about testing:
- The purpose of a test is to deliver us knowledge about the system, and knowledge has different levels of value. Continue reading