Agent Skills: Prompt Testing

A/B testing and performance metrics for prompts

UncategorizedID: fusengine/agents/prompt-testing

Install this agent skill to your local

pnpm dlx add-skill https://github.com/fusengine/agents/tree/HEAD/plugins/prompt-engineer/skills/prompt-testing

Skill Files

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plugins/prompt-engineer/skills/prompt-testing/SKILL.md

Skill Metadata

Name
prompt-testing
Description
"A/B testing and performance metrics for prompts. Use when: comparing two prompt variants, defining quality/efficiency/robustness metrics, or deciding whether to adopt a challenger prompt over a baseline."

Prompt Testing

Skill for testing, comparing, and measuring prompt performance.

References

  • metrics.md - Load when: defining or scoring Quality/Efficiency/Robustness/UX metrics with thresholds and calculation formulas
  • methodology.md - Load when: running a full A/B test (hypothesis, dataset sizing, statistical significance, common pitfalls)
  • templates.md - Load when: writing a test dataset JSON or an A/B test report

Testing Workflow

1. DEFINE
   └── Test objective
   └── Metrics to measure
   └── Success criteria

2. PREPARE
   └── Variants A and B
   └── Test dataset
   └── Baseline (if existing)

3. EXECUTE
   └── Run on dataset
   └── Collect results
   └── Document observations

4. ANALYZE
   └── Calculate metrics
   └── Compare variants
   └── Identify patterns

5. DECIDE
   └── Recommendation
   └── Statistical confidence
   └── Next iterations

Performance Metrics

Quality

| Metric | Description | Calculation | |--------|-------------|-------------| | Accuracy | Correct responses | Correct / Total | | Compliance | Format adherence | Compliant / Total | | Consistency | Response stability | 1 - Variance | | Relevance | Meeting the need | Average score (1-5) |

Efficiency

| Metric | Description | Calculation | |--------|-------------|-------------| | Tokens Input | Prompt size | Token count | | Tokens Output | Response size | Token count | | Latency | Response time | ms | | Cost | Price per request | Tokens × Price |

Robustness

| Metric | Description | Calculation | |--------|-------------|-------------| | Edge Cases | Edge case handling | Passed / Total | | Jailbreak Resist | Bypass resistance | Blocked / Attempts | | Error Recovery | Error recovery | Recovered / Errors |

For full definitions, thresholds, and the UX metrics category, see metrics.md. For the test dataset and report formats, see templates.md.

Commands

# Create a test
/prompt test create --name "Test v1" --dataset tests.json

# Run an A/B test
/prompt test run --a prompt_a.md --b prompt_b.md --dataset tests.json

# View results
/prompt test results --id test_001

# Compare two tests
/prompt test compare --tests test_001,test_002

Decision Criteria

When to adopt variant B?

IF:
  - Accuracy B >= Accuracy A
  AND (Tokens B <= Tokens A * 1.1 OR accuracy improvement > 5%)
  AND no regression on edge cases
THEN:
  → Adopt B

ELSE IF:
  - Accuracy improvement > 10%
  AND token regression < 20%
THEN:
  → Consider B (acceptable trade-off)

ELSE:
  → Keep A or iterate

Best Practices

  1. Minimum 20 test cases for significance
  2. Include edge cases (15-20% of dataset)
  3. Test multiple runs for consistency
  4. Document hypotheses before testing
  5. Version the prompts being tested