Testing vs Validation vs Evaluation

Confusing these three terms in the C1-2 writing test or C1-3 interview drops marks instantly — Testing and Validation both live in Development, while Evaluation is its own stage.

The three at a glance

Term	PSM stage	Purpose	Concrete example
Testing	Development	Does the program run correctly?	Entering `25` into an age field gives the expected output
Validation	Development	Is the input reasonable before processing?	Rejecting `−3` or `"abc"` as an age before any calculation runs
Evaluation	Evaluation	Does the finished solution meet its criteria?	"Does it satisfy all functional requirements listed in the SRS?"

Testing

Testing checks that the program runs correctly — given an input, does it produce the expected output? You write test cases before or during coding and run them as you build. Testing catches bugs: wrong calculations, broken logic, features that don't behave as designed. It happens inside the Development stage.

Example: Enter 25 into an age field and expect a calculated result. If the output matches the design, the test passes. If the program crashes or returns the wrong value, testing has found a bug to fix.

Validation

Validation checks that data entered by the user is reasonable before the program processes it. It runs at the point of input — not after — and prevents garbage data from reaching the rest of the program. Like testing, validation is part of the Development stage.

Example: The age field should reject −3. Validation code checks for this (if age < 0: display error) and stops the bad value from being used in any calculation.

Key distinction: testing checks whether the program works; validation checks whether the data is acceptable.

Evaluation

Evaluation judges whether the completed solution meets the evaluation criteria set during the Design stage. It is PSM Stage 4 — separate from Development. You are not checking individual inputs or features; you are assessing the solution as a whole against measurable standards.

Example: "Does the finished app allow 90% of beta testers to complete onboarding in under 2 minutes?" That criterion was written in Design. Evaluation collects evidence (surveys, observation, usage data) and checks whether it was met.

Common mistake: saying your solution "works" as part of Evaluation. Whether it works is testing. Evaluation asks whether it meets user needs and requirements.

Why it matters at validation

The C1-2 writing test and C1-3 interview both probe PSM knowledge directly. A question like "which Development activities does your project plan include?" expects you to name validation, testing, and documentation separately — not lump them together. At the C1-3 interview you may be asked to point to evidence of each activity in your GitHub Projects board. If your plan only shows "testing" with no separate validation tasks, that signals a gap. At Stage 4, markers check that you are measuring against your Design-stage criteria, not just describing whether the app runs.

See C013-Annotate-Project-Plan.md for guidance on annotating your plan so each PSM activity is visible to the interviewer.