Establish the outside behaviour.
Begin with what the user-facing boundary is actually doing, not what the internal configuration says it should be doing.
METHODS / WORKING PROCESS
Observe first.
Change second.
Narrow the path.
Work inward one boundary at a time until the behaviour changes.
Change one variable.
Small changes make cause and effect easier to distinguish.
Verify again from outside.
Internal success is not enough until the public behaviour matches the intended result.