Is there a formal enumeration of the ways that components can be coupled / depend on eachother?

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What would help when refactoring a large method to ensure that I don’t break anything?

I’m currently refactoring a part of a large codebase with no unit tests whatsoever. I tried to refactor code the brute way, i.e. by trying to guess what the code is doing and what changes wouldn’t change it meaning, but without success: it randomly breaks features all around the codebase.

Are there any formalized/mathematical theories of software testing?

Googling “software testing theory” only seems to give theories in the soft sense of the word; I have not been able to find anything that would classify as a theory in the mathematical, information theoretical or some other scientific field’s sense.

How “Best” to capture State Transitions in a formal software requirements specification

Suppose you have a state transition diagram. What is the best way to “Formally” write requirement(s) that capture the state transitions depicted in the diagram. Over the years I have used two approaches and both work, but each time I work with new people there seems to be disagreements on how best to “Formally” capture the state transitions. “Formally” capture is required because traceability matrices are used that map to “Test Cases” and “Software Units (ie. Classes and/or Modules)”.

Is “Unit testing” a form of formal method?

After some research, I understand that:

Is “Unit testing” a form of formal method?

After some research, I understand that:

Is “Unit testing” a form of formal method?

After some research, I understand that:

Is “Unit testing” a form of formal method?

After some research, I understand that: