Testing Glossary — 50 Terms Explained Simply

One line per term. Alphabetical order.

A

Acceptance criteria — The conditions a feature must meet to be accepted as "done".
Ad-hoc testing — Informal testing without a plan or documentation, based on the tester's intuition.
Agile — A way of building software in short cycles (sprints) with frequent feedback.
API (Application Programming Interface) — A way for programs to talk to each other; testers check APIs with tools like Postman.
Assertion — A check in an automated test: "this value must equal that value".
Automation testing — Running tests with scripts and tools instead of by hand.

Black-box testing — Testing without seeing the code; you only check inputs and outputs.
Boundary value analysis — Testing at the edges of allowed values (e.g. if 1–100 is allowed, test 0, 1, 100, 101).
Bug / Defect — A problem in the software: the actual behavior is different from the expected behavior.
Bug life cycle — The journey of a bug: New → Open → Fixed → Retested → Closed (sometimes Reopened).
Build — A specific version of the software given to testers (e.g. "build 2.4.1").

CI/CD (Continuous Integration / Continuous Delivery) — Automatically building, testing, and releasing code after every change.
Checkpoint / Verification point — A specific thing you check during a test.
Coverage (test coverage) — How much of the requirements or code is covered by tests.

End-to-end (E2E) testing — Testing a complete user flow from start to finish, like a real user.
Entry criteria — Conditions that must be true before testing can start.
Environment — Where the software runs for testing (e.g. staging, production).
Equivalence partitioning — Dividing test data into groups where all values behave the same, and testing one value per group.
Exit criteria — Conditions that must be true to finish testing (e.g. "no open critical bugs").
Exploratory testing — Testing without a script: you design and run tests at the same time, guided by curiosity.

False positive — A test says "Fail" but the software is actually fine (bad test).
Functional testing — Testing what the software DOES (features, behavior).

Gray-box testing — Testing with partial knowledge of the code (between black-box and white-box).

Integration testing — Testing that different parts of the system work together.
ISTQB — International Software Testing Qualifications Board; offers the most common testing certificates.

Load testing — Checking how the system behaves under heavy use (many users at once).

Manual testing — Testing by hand, without automation scripts.
Mock / Stub — A fake version of a component used in testing when the real one isn't available.

Negative testing — Testing with invalid input to check the system handles errors correctly.
Non-functional testing — Testing HOW the software works: performance, security, usability.

Positive testing — Testing with valid input to check the system works as expected.
Priority — How soon a bug should be fixed (business decision).
Production — The live environment where real users use the software.

Regression testing — Re-running tests after a change to check that old functionality still works.
Release — Delivering a version of the software to users.
Requirement — A description of what the software must do.

Sanity testing — A narrow, focused check of one area after a small fix.
Severity — How serious a bug is technically (crash vs typo).
Smoke testing — A quick check that the main features work on a new build.
Sprint — A short, fixed time period in Agile (usually 2 weeks) in which a set of work is done.
Staging — A test environment that looks like production.
STLC (Software Testing Life Cycle) — The phases of testing work: analysis, planning, design, execution, closure.
System testing — Testing the complete, whole application.

Test case — A documented set of steps, data, and expected results for one check.
Test data — The input values used in tests (users, files, amounts).
Test plan — A document describing what, how, when, and who will test.
Test scenario — A high-level idea of what to test (one scenario can become many test cases).
Test suite — A collection of test cases grouped together.
Traceability — The link between a requirement and the test cases that check it.

UAT (User Acceptance Testing) — Final testing done by users or business people before go-live.
Unit testing — Testing the smallest piece of code alone; usually done by developers.
Usability testing — Checking if the software is easy and pleasant to use.

Validation — "Are we building the RIGHT product?" (does it meet user needs).
Verification — "Are we building the product RIGHT?" (does it match the requirements).
White-box testing — Testing with knowledge of the code inside.

💡 Missing a term? The official ISTQB glossary is free and complete: https://glossary.istqb.org/