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Last active Dec 17, 2015
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Kicking the Tires

Modifying Programs

When modifying a program, or when reviewing a modification of a program, you will want to consider at least the following:

  1. Tests
  • Is the modification tested?
  • Can you prove that the tests cover both the pre-modification and post-modification states of the program correctly? Do it.
  1. Interface
  • Does the modification change the interface of the code?
  • If so, are all possible callers prepared for the change?
  • What implications does the interface change have for versioning and dependencies?
  • Stepping back, is the new interface still well-designed as a whole (does the modification fit in)?
  1. Rules/Logic
  • Does the modification change the rules or logic of the program itself?
  • How is the program's data affected by the change in logic, both for callers (side effects) and downstream code?
  • Does the modification conform to the general style of code used elsewhere in the program?
  • Is the modification the simplest and most explicit way of achieving the result?
  1. Errors
  • What possible errors or exceptions can surface from the program's internal logic or operations (think divide by zero, internal validation checks)?
  • What possible errors or exceptions can surface from the program's dependencies (think network, DB, disk, memory, external validation, schema mismatch)?
  1. Storage
  • Is the program storing data in a datastore (or just local memory)?
  • If so, how much data is being stored?
  • Does the modification change the type or amount of data stored?
  • Is the program's data converted by the interface with the data store (e.g. Redis converting to strings)?
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