Individual skill
principle-test-behavior-not-implementation
Use when writing or changing a test, or deciding whether one should stay. Check what callers can see through the interface they call, so the test breaks when behavior breaks and survives changes to internals alone.
plugins/requie/endostack/skills/principle-test-behavior-not-implementation/SKILL.md
Source commit d780783eba4ecc7c8b9429f95c9362df95f07c61
What was checked
- Matches the observed repository HEAD
- Yes
- Scanner rules are current
- Yes
- Repository scan complete
- No
- Skill scan complete
- No
- Observed behavior
- Network or broad shell
- Last checked
- Nov 4, 2026
These are observations at the recorded commit, not a guarantee of safety. Review the source before running it.
Install this skill
Choose an agent in your Stack or copy a command below. Commands fetch the pinned commit and copy only this skill directory. Existing destinations are refused. Copying a command does not install anything.
An install command is unavailable: current rules, complete repository and skill scans, an eligible behavior level and a permitted license are required.
Repository context
- Repository stars (not skill ratings)
- 1,532
- Repository last updated
- Nov 6, 2026
- License
- Apache-2.0
Observed agent integration: No specific integration evidence. Standard SKILL.md installation does not imply verified compatibility.
- ai-coding Repository topic
- awesome Repository topic
- awesome-list Repository topic
- codex Repository topic
- codex-plugins Repository topic
- openai Repository topic
- codex-skill Repository topic
- codex-skills Repository topic
- marketplace Repository topic
- codex-marketplace Repository topic
- writing Derived category
- testing Derived category
Files and excerpt
File metadata and permitted, redacted excerpts come from the recorded scan. Source links are pinned to that commit.
Browse files
SKILL.mdcore · 3,818 bytes
Read excerpt
# Test behavior, not implementation
A test should check results visible to the code's users via the interface they call. It should fail once that visible behavior breaks and stay green when nothing but the internals move.
## When it applies
Writing a test, changing one, or deciding whether to keep one.
## Terms
- **Users**: callers, end users, and other services.
- **Behavior**: whatever users can observe. That covers return values, thrown errors, state they can read back afterwards, and effects on external systems (an outgoing request, a database row, a published message).
- **Implementation**: everything they cannot see, meaning private helpers, the order of internal calls, intermediate data, and which internal component performed the work.
