Understanding what you did not write.
WHY IT MATTERS
You will inherit code in languages you do not know.
WHAT TO ESTABLISH FIRST
What the program is for Where execution begins How it is built and run
WHAT TO LOOK FOR
The structure: how files and directories are organised
Dependencies declared Configuration Tests, which document intended behaviour
WHY TESTS FIRST
They show what the code is supposed to do, in examples.
WHAT TO TRACE
One path through the program, from entry to output.
WHY ONE PATH
It teaches more than reading everything superficially.
WHAT TO IGNORE INITIALLY
Syntax you do not recognise, if the intent is clear from context.
WHAT TO LOOK UP
Constructs appearing repeatedly.
WHAT TO USE
An editor with navigation, so you can follow definitions.
WHAT TO DO BEFORE CHANGING ANYTHING
Get it running Get its tests passing Make a trivial change and observe the effect
WHAT TO RECORD
Notes of what you learn, since you will need them again.
