Test Writer
axelixlabs/axelix
Writes new tests for Axelix source code (Java, Kotlin, TypeScript, JavaScript) that follow the project's testing standards — public-API contract coverage, test isolation, given/when/then structure…
Automatically generates executable test cases from model checking counterexample traces.
Install Counterexample To Test Generator
$ npx skills add ArabelaTso/Skills-4-SE --skill counterexample-to-test-generator -a claude-codeProject install by default; add -g for ~/.claude/skills/.
$ gh skill install ArabelaTso/Skills-4-SE counterexample-to-test-generator --agent claude-codeProject scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).
$ git clone --depth 1 https://github.com/ArabelaTso/Skills-4-SE.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/counterexample-to-test-generator .claude/skills/counterexample-to-test-generator && rm -rf skills-srcUse ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.
Claude Code skills documentation · loads skills from .claude/skills/
Install the "counterexample-to-test-generator" agent skill from https://github.com/ArabelaTso/Skills-4-SE/tree/main/skills/counterexample-to-test-generator into .claude/skills/counterexample-to-test-generator/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "counterexample-to-test-generator", then confirm the skill loads.Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$skill-installer install https://github.com/ArabelaTso/Skills-4-SE/tree/main/skills/counterexample-to-test-generatorType this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.
$ npx skills add ArabelaTso/Skills-4-SE --skill counterexample-to-test-generator -a codexProject install goes to .agents/skills/; add -g for ~/.codex/skills/.
$ gh skill install ArabelaTso/Skills-4-SE counterexample-to-test-generator --agent codexProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/ArabelaTso/Skills-4-SE.git skills-src && mkdir -p .agents/skills && cp -r skills-src/skills/counterexample-to-test-generator .agents/skills/counterexample-to-test-generator && rm -rf skills-srcUse ~/.agents/skills/ instead of .agents/skills for a personal install.
Codex skills documentation · loads skills from .agents/skills/
Install the "counterexample-to-test-generator" agent skill from https://github.com/ArabelaTso/Skills-4-SE/tree/main/skills/counterexample-to-test-generator into .agents/skills/counterexample-to-test-generator/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "counterexample-to-test-generator", then confirm the skill loads.Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add ArabelaTso/Skills-4-SE --skill counterexample-to-test-generator -a cursorProject install goes to .agents/skills/; add -g for ~/.cursor/skills/.
$ gh skill install ArabelaTso/Skills-4-SE counterexample-to-test-generator --agent cursorProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/ArabelaTso/Skills-4-SE.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/skills/counterexample-to-test-generator .cursor/skills/counterexample-to-test-generator && rm -rf skills-srcUse ~/.cursor/skills/ instead of .cursor/skills for a personal install.
Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/
Install the "counterexample-to-test-generator" agent skill from https://github.com/ArabelaTso/Skills-4-SE/tree/main/skills/counterexample-to-test-generator into .cursor/skills/counterexample-to-test-generator/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "counterexample-to-test-generator", then confirm the skill loads.Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gemini skills install https://github.com/ArabelaTso/Skills-4-SE.git --path skills/counterexample-to-test-generator--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.
$ npx skills add ArabelaTso/Skills-4-SE --skill counterexample-to-test-generator -a gemini-cliProject install goes to .agents/skills/; add -g for ~/.gemini/skills/.
$ gh skill install ArabelaTso/Skills-4-SE counterexample-to-test-generator --agent gemini-cliProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/ArabelaTso/Skills-4-SE.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/skills/counterexample-to-test-generator .gemini/skills/counterexample-to-test-generator && rm -rf skills-srcUse ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.
Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/
Install the "counterexample-to-test-generator" agent skill from https://github.com/ArabelaTso/Skills-4-SE/tree/main/skills/counterexample-to-test-generator into .gemini/skills/counterexample-to-test-generator/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "counterexample-to-test-generator", then confirm the skill loads.Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gh skill install ArabelaTso/Skills-4-SE counterexample-to-test-generatorInstalls for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).
$ npx skills add ArabelaTso/Skills-4-SE --skill counterexample-to-test-generator -a github-copilotProject install goes to .agents/skills/; add -g for ~/.copilot/skills/.
$ git clone --depth 1 https://github.com/ArabelaTso/Skills-4-SE.git skills-src && mkdir -p .github/skills && cp -r skills-src/skills/counterexample-to-test-generator .github/skills/counterexample-to-test-generator && rm -rf skills-srcUse ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.
GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/
Install the "counterexample-to-test-generator" agent skill from https://github.com/ArabelaTso/Skills-4-SE/tree/main/skills/counterexample-to-test-generator into .github/skills/counterexample-to-test-generator/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "counterexample-to-test-generator", then confirm the skill loads.GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add ArabelaTso/Skills-4-SE --skill counterexample-to-test-generator -a opencodeOpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.
$ gh skill install ArabelaTso/Skills-4-SE counterexample-to-test-generator --agent opencodeProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/ArabelaTso/Skills-4-SE.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/skills/counterexample-to-test-generator .opencode/skills/counterexample-to-test-generator && rm -rf skills-srcUse ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.
OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/
Install the "counterexample-to-test-generator" agent skill from https://github.com/ArabelaTso/Skills-4-SE/tree/main/skills/counterexample-to-test-generator into .opencode/skills/counterexample-to-test-generator/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "counterexample-to-test-generator", then confirm the skill loads.OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
Facts
- Skill name
counterexample-to-test-generator- GitHub stars
- 253
- Token cost
- ~1.6k tokens
- SKILL.md length
- 524 words
- Files
- 8 (incl. references, assets)
- Skills in repo
- 170
- Repo updated
- First seen
- Licence
- Apache-2.0
At a glance
Automatically generates executable test cases from model checking counterexample traces.
- Works in 5 steps: Analyze Inputs → Map Abstract States to Concrete Values → Generate Test Structure → …
- Working with model checker outputs (SPIN
- SKILL.md covers Overview, Workflow, Example Workflow and Best Practices, plus 2 more sections
- Runs C#, Java and Python scripts from its folder
What it does
Counterexample To Test Generator is an agent skill from ArabelaTso/Skills-4-SE. Automatically generates executable test cases from model checking counterexample traces. Translates abstract counterexample states and transitions into concrete test inputs, execution steps, and assertions that reproduce property violations. Use when working with model checker outputs (SPIN, CBMC, NuSMV, TLA+, Java PathFinder, etc.) and needing to create regression tests, validate bug fixes, or reproduce verification failures in executable test suites.
Its SKILL.md is about 1.6k tokens, which your agent loads only when the skill is triggered. The skill folder holds 10 other files, including reference files and assets (for example `assets/test_templates/README.md`, `assets/test_templates/python_pytest_template.py` and `references/model_checker_formats.md`).
It sits in Testing & QA, covering Test generation and Debugging. It works with Java. The repository describes itself as: A curated list of 180+ useful Claude Skills for Software Engineering and resources for customizing AI for SE workflows. The licence is Apache-2.0.
When your agent uses it
- Working with model checker outputs (SPIN
- Java PathFinder
- Etc.) and needing to create regression tests
- Validate bug fixes
Example prompts
- “/counterexample-to-test-generator”
Requirements
- Python 3
Workflow steps
5 steps, taken from the step headings in SKILL.md.
What it can do on your machine
Read from SKILL.md and the folder at commit 4f38503. It shows what the files ask for, not the result of running them.
Tool permissions
Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.
From allowed-tools in the SKILL.md frontmatter.
Runs code
Ships script files (C#, Java and Python), which the agent can run.
From the folder's file list and the shell code blocks in SKILL.md.
Network
No URLs in SKILL.md.
From URLs in SKILL.md, links to its own repository left out.
Credentials
Names no API keys, tokens, secrets or passwords.
From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.
Context cost
Counterexample To Test Generator loads about 1.6k tokens when it runs, and up to ~3.2k if it reads all its reference files. Until then it costs about 122 tokens; SKILL.md has 524 words of instructions outside code blocks.
Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.
Safety
Auto-check passed
The automated check found no risky patterns in SKILL.md.
Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.
SKILL.md
The full file from ArabelaTso/Skills-4-SE at commit 4f38503, republished under its Apache-2.0 licence (© ArabelaTso). 524 words, ~1,573 tokens.
Download SKILL.mdSave it as
.claude/skills/counterexample-to-test-generator/SKILL.md (or your agent's skills folder). This skill also uses 7 other files; get the full folder from GitHub.- name
- counterexample-to-test-generator
- description
- Automatically generates executable test cases from model checking counterexample traces. Translates abstract counterexample states and transitions into concrete test inputs, execution steps, and assertions that reproduce property violations. Use when working with model checker outputs (SPIN, CBMC, NuSMV, TLA+, Java PathFinder, etc.) and needing to create regression tests, validate bug fixes, or reproduce verification failures in executable test suites.
Counterexample To Test Generator
Overview
This skill transforms counterexample traces from model checkers into executable test cases that reliably reproduce property violations. It bridges formal verification and testing by mapping abstract states to concrete values and generating runnable tests with clear traceability from counterexample steps to test logic.
Workflow
Step 1: Analyze Inputs
Gather and understand the counterexample trace and program:
Identify the model checker format: Determine which tool produced the counterexample (SPIN, CBMC, NuSMV, TLA+, JPF, etc.). See references/model_checker_formats.md for format details.
Extract key information:
- Initial state values
- Sequence of transitions/steps
- Variable values at each step
- Property violation point
- Error condition or assertion failure
Understand the program structure:
- Entry points and function signatures
- Input parameters and their types
- State variables involved in the trace
- Control flow relevant to the counterexample
Step 2: Map Abstract States to Concrete Values
Translate the counterexample's abstract representation into concrete test inputs:
Determine concrete values for abstract state variables:
- Map symbolic values to concrete instances
- Resolve non-deterministic choices to specific values
- Handle ranges and constraints from the model
Identify input sequences:
- Extract the sequence of function calls or operations
- Determine parameter values for each call
- Identify timing or ordering constraints
Handle environment assumptions:
- External inputs or system calls
- Concurrency or scheduling decisions
- Resource states (files, network, memory)
Step 3: Generate Test Structure
Create the test case framework in the target language:
Choose test framework based on the program language:
- C/C++: Google Test, CUnit, Check
- Java: JUnit, TestNG
- Python: pytest, unittest
- C#: NUnit, xUnit
Structure the test:
- Setup phase: Initialize state to match counterexample start
- Execution phase: Replay the counterexample sequence
- Assertion phase: Verify the property violation occurs
Add traceability comments: Map each test step to counterexample steps for debugging and maintenance.
Step 4: Implement Test Logic
Write the executable test code:
Setup code:
// Initialize variables to counterexample initial state // Set up test fixtures or mocks // Configure environment (if needed)Execution sequence:
// Step 1 (CE line X): [description] // Execute operation with concrete values // Step 2 (CE line Y): [description] // Execute next operationAssertions:
// Verify property violation (CE line Z) // Assert expected failure condition // Check final state matches counterexample
Show full SKILL.md (210 more words)Show less
Step 5: Generate Output
Produce the complete test case with documentation:
- Test file: Complete, compilable/runnable test code
- Mapping document: Table linking counterexample steps to test lines
- Execution instructions: How to compile and run the test
- Expected behavior: What the test should demonstrate (failure reproduction)
Example Workflow
Input: SPIN counterexample showing a deadlock in a concurrent system
Output:
// test_deadlock.c - Reproduces deadlock from SPIN counterexample trail
#include <pthread.h>
#include <assert.h>
// Counterexample mapping:
// CE Step 1-2: Thread 1 acquires lock A
// CE Step 3-4: Thread 2 acquires lock B
// CE Step 5: Thread 1 waits for lock B (blocks)
// CE Step 6: Thread 2 waits for lock A (deadlock)
void* thread1_func(void* arg) {
pthread_mutex_lock(&lock_a); // CE Step 1
sleep(1); // CE Step 2 (timing)
pthread_mutex_lock(&lock_b); // CE Step 5 (blocks)
// ... rest of test
}
void test_deadlock_scenario() {
// Setup: Initialize locks (CE initial state)
pthread_mutex_init(&lock_a, NULL);
pthread_mutex_init(&lock_b, NULL);
// Execute: Create threads in counterexample order
pthread_create(&t1, NULL, thread1_func, NULL);
pthread_create(&t2, NULL, thread2_func, NULL);
// This test will hang, demonstrating the deadlock
pthread_join(t1, NULL); // Will timeout
}Best Practices
- Minimize test complexity: Generate the simplest test that reproduces the violation
- Preserve causality: Maintain the exact sequence from the counterexample
- Make violations obvious: Use clear assertions and error messages
- Add context: Include comments explaining the property being violated
- Handle non-determinism: Document any assumptions made when concretizing values
- Test the test: Verify the generated test actually fails as expected
Common Challenges
Challenge: Counterexample uses symbolic values without concrete bounds Solution: Use representative values from the domain, document the choice
Challenge: Trace involves complex timing or scheduling Solution: Use synchronization primitives or explicit delays to enforce ordering
Challenge: Program state is partially specified in counterexample Solution: Initialize unspecified variables to default/neutral values
Challenge: Counterexample is very long Solution: Identify the minimal prefix that still triggers the violation
References
- references/model_checker_formats.md: Detailed format specifications for common model checkers
- assets/test_templates/: Test framework templates for various languages
© ArabelaTso, Apache-2.0. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file
Files
SKILL.md and 7 other files (references, assets) in skills/counterexample-to-test-generator of ArabelaTso/Skills-4-SE.
- SKILL.md
- assets/test_templates/README.md
- assets/test_templates/c_gtest_template.c
- assets/test_templates/cpp_gtest_template.cpp
- assets/test_templates/csharp_nunit_template.cs
- assets/test_templates/java_junit_template.java
- assets/test_templates/python_pytest_template.py
- references/model_checker_formats.md
Open the folder on GitHubat commit 4f38503
Compare with similar skills
Counterexample To Test Generator next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.
| Skill | Stars | Used in | Tokens | Auto-check | Licence | Repo updated |
|---|---|---|---|---|---|---|
| Counterexample To Test Generator this skillArabelaTso/Skills-4-SE | 253 | — | ~1.6k | Automated safety check: Pass | Apache-2.0 | |
| Test Writeraxelixlabs/axelix | 148 | — | ~2.2k | Automated safety check: Pass | LGPL-3.0 | |
| Code SolvingHoangTheQuyen/think-better | 122 | — | ~3.7k | Automated safety check: Pass | MIT | |
| Debug Surefireeclipse-rdf4j/rdf4j | 420 | — | ~2.4k | Automated safety check: Pass | BSD-3-Clause | |
| QABuilderIO/agent-native | 7.1k | — | ~3k | Automated safety check: Notes | None | |
| Test BlindspotsNeeeophytee/finding-unknowns-skills | 343 | — | ~676 | Automated safety check: Pass | MIT |
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Questions about Counterexample To Test Generator
What does Counterexample To Test Generator do?
Automatically generates executable test cases from model checking counterexample traces. Counterexample To Test Generator is an agent skill from ArabelaTso/Skills-4-SE. Automatically generates executable test cases from model checking counterexample traces.
When should I use Counterexample To Test Generator?
Counterexample To Test Generator fits situations like: working with model checker outputs (SPIN; java PathFinder; etc.) and needing to create regression tests; validate bug fixes.
How do I install Counterexample To Test Generator in Claude Code?
Run `npx skills add ArabelaTso/Skills-4-SE --skill counterexample-to-test-generator -a claude-code`. Or copy the skill folder (skills/counterexample-to-test-generator in ArabelaTso/Skills-4-SE) into .claude/skills/counterexample-to-test-generator in your project. Claude Code loads it when a task matches its description.
How do I install Counterexample To Test Generator in Codex?
Run `npx skills add ArabelaTso/Skills-4-SE --skill counterexample-to-test-generator -a codex`. Or copy the skill folder (skills/counterexample-to-test-generator in ArabelaTso/Skills-4-SE) into .agents/skills/counterexample-to-test-generator in your project. Codex loads it when a task matches its description.
Can I use Counterexample To Test Generator in Cursor, Gemini CLI or GitHub Copilot?
Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add ArabelaTso/Skills-4-SE --skill counterexample-to-test-generator -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/counterexample-to-test-generator, .gemini/skills/counterexample-to-test-generator, .github/skills/counterexample-to-test-generator and .opencode/skills/counterexample-to-test-generator in your project.
What does Counterexample To Test Generator need to run?
Going by SKILL.md and its folder, Counterexample To Test Generator needs C#, Java and Python for the scripts in its folder. Our summary lists: Python 3.
Does Counterexample To Test Generator access the network?
SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.
Is Counterexample To Test Generator safe to install?
Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.
What licence does Counterexample To Test Generator use?
Counterexample To Test Generator is published under the Apache-2.0 licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.
How many tokens does Counterexample To Test Generator use?
About 1.6k tokens (SKILL.md is roughly 6.3k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 1.6k tokens, read only when the agent opens those files.
What are the alternatives to Counterexample To Test Generator?
Skills that share tags, products or a category with Counterexample To Test Generator: Test Writer (axelixlabs/axelix, 148 stars), Code Solving (HoangTheQuyen/think-better, 122 stars), Debug Surefire (eclipse-rdf4j/rdf4j, 420 stars) and QA (BuilderIO/agent-native, 7.1k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.
Who maintains Counterexample To Test Generator?
ArabelaTso (a GitHub user) maintains it in ArabelaTso/Skills-4-SE, which has 253 GitHub stars. The repository holds 170 skills in this directory. The repository was last updated on August 21, 2026.
Source: ArabelaTso/Skills-4-SE on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.