behavior-preservation-checker

Compare runtime behavior between original and migrated repositories to detect behavioral differences, regressions, and semantic changes. Use when validating code migrations, refactorings, language ports, framework upgrades, or any transformation that should preserve behavior. Automatically compares test results, execution traces, API responses, and observable outputs between two repository versions. Provides actionable guidance for fixing deviations and ensuring behavioral equivalence.

Install with Tessl CLI

npx tessl i github:ArabelaTso/Skills-4-SE --skill behavior-preservation-checker

What are skills?

Review — 78%

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Learn more

Validation — 11 / 11 Passed

Validation for skill structure

SKILL.md

Review

Evals

Evaluation results

95%

70%

Validate a Refactored Statistics Library

Test-based comparison workflow

Criteria

Without context

With context

pytest json-report flag

100%

json-report-file flag

100%

compare_test_results.py usage

50%

Report behavioral_equivalence

50%

100%

Report summary fields

100%

Severity classification

100%

Differences list

100%

Recommendations list

100%

Separate result files

100%

Variance regression identified

100%

Without context: $0.4355 · 5m 54s · 22 turns · 27 in / 6,918 out tokens

With context: $1.1129 · 3m 43s · 39 turns · 4,129 in / 11,614 out tokens

96%

73%

Validate a Ported String Processing Library

behavior_checker.py orchestrator and report format

Criteria

Without context

With context

behavior_checker.py invocation

41%

66%

behavior_report.json created

100%

Report summary section

20%

100%

passed_original_failed_migrated count

100%

Differences array

100%

Severity on differences

100%

Critical severity regression

100%

Recommendations array

100%

Guidance on differences

100%

behavioral_equivalence percentage

100%

Workflow log

100%

Without context: $0.6131 · 4m 31s · 25 turns · 32 in / 9,137 out tokens

With context: $1.1942 · 4m 51s · 40 turns · 4,088 in / 15,387 out tokens

100%

35%

Validate a Migrated Sorting and Search Library

Property-based testing and multi-method comparison

Criteria

Without context

With context

hypothesis import

100%

@given decorator used

100%

strategies used

100%

Equivalence assertion in property tests

50%

100%

Multiple comparison methods

100%

Tolerance threshold applied

100%

behavior_report.json present

100%

Report differences populated

100%

Report recommendations

100%

Severity levels present

100%

comparison_notes.md present

100%

Without context: $1.2700 · 9m 27s · 38 turns · 42 in / 20,108 out tokens

With context: $2.6824 · 12m 26s · 58 turns · 2,199 in / 31,020 out tokens

Evaluated: about 11 hours ago
Agent: Claude Code

Table of Contents

Validate a Refactored Statistics Library Validate a Ported String Processing Library Validate a Migrated Sorting and Search Library

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