buff-test v2

Coverage-aware smart testing with change-aware selection and context-informed generation. Uses the project dependency graph to track what's tested, what's not, and what needs retesting when code changes — then generates tests informed by real caller data, past corrections, and known edge cases.

Framework detection

Detect in this order (stop at first match):

File	Framework
vitest.config.*	Vitest
jest.config.*	Jest
pytest.ini / pyproject.toml with [tool.pytest]	pytest
Cargo.toml with [dev-dependencies] test crates	Rust built-in
*_test.go files present	Go built-in
bun.lockb and no config	Default to Vitest
package.json only	Default to Vitest
requirements.txt only	Default to pytest

After detection, write to .buff/memory/context.json:

{ "test_framework": "vitest" }

On subsequent runs, read from context.json and skip detection.

Coverage tracking via graph

Uses .buff/memory/graph.json for a live coverage map — no external coverage tools required.

Function-level coverage check:

1. Read the target file's entry in graph.json to get its exports list
2. If a test_file is mapped, Grep the test file for references to each exported symbol
3. Mark each export as tested (referenced in test file) or untested (not referenced)
4. Update the file's coverage field in graph.json:

{
  "coverage": {
    "functions": 3,
    "tested": 2,
    "untested": ["createSession"]
  }
}

This runs automatically after test generation and can be triggered manually with --coverage.

Scope handling

Invocation	Scope
/buff:test	Test the last modified file
/buff:test src/auth.ts	Test the specified file
/buff:test --coverage	Show project coverage map
/buff:test --gaps	Untested exports ranked by risk
/buff:test --changed	Test only changed files + dependents
/buff:test --run	Generate and immediately run

--coverage output

Read .buff/memory/graph.json — for each file entry, extract only exports, coverage, and imported_by count (skip imports_from, lines, last_modified to save tokens). Compute coverage from the coverage field. Display:

## Test Coverage — project-wide

| File | Exports | Tested | Gap | Risk |
|---|---|---|---|---|
| src/auth.ts | 3 | 2 (67%) | createSession | HIGH — 3 dependents |
| src/db.ts | 4 | 1 (25%) | connect, query, close | HIGH — foundation |
| src/utils.ts | 8 | 6 (75%) | formatDate, retry | LOW — leaf |

Overall: 20/28 exports tested (71%)
Critical gaps: 2 files below 50% with dependents

Risk is determined by imported_by count in graph.json:

• HIGH — 3+ dependents, or 0 dependents but is imported by HIGH-risk files (foundation module)
• MEDIUM — 1-2 dependents
• LOW — 0 dependents (leaf module)

Files with no imported_by entries and no dependents are leaf modules. Files imported by many others are foundation modules — untested foundation code is always HIGH risk.

--gaps risk ranking

Read graph.json — extract only exports, coverage.untested, and imported_by count per file. Collect all untested exports across the project. Rank by risk — number of dependents from the imported_by field determines priority.

Risk formula: Untested export in a foundation module (many dependents) > untested export in a mid-tier module > untested export in a leaf utility.

Output a ranked list with risk justification:

## Untested Exports — ranked by risk

1. src/db.ts → connect, query, close
   Risk: CRITICAL — foundation module, 6 dependents, 25% coverage
   Dependents: auth.ts, users.ts, posts.ts, comments.ts, admin.ts, migrations.ts

2. src/auth.ts → createSession
   Risk: HIGH — 3 dependents, 67% coverage
   Dependents: router.ts, middleware.ts, admin.ts

3. src/utils.ts → formatDate, retry
   Risk: LOW — leaf module, 0 dependents, 75% coverage

Action: Run `/buff:test src/db.ts` to address the highest-risk gap.

--changed workflow

Change-aware test selection — run only what's affected by recent changes.

Steps:

1. Run git diff --name-only to get changed files (staged + unstaged)
2. For each changed file, look up its test_file from graph.json
3. For each changed file, look up its imported_by from graph.json to find dependents
4. For each dependent, look up its test_file from graph.json
5. Deduplicate the test file list
6. Run only the affected test files

Example output:

Changed: src/auth.ts
  Direct test: src/auth.test.ts
  Dependents: src/router.ts, src/middleware.ts
  Dependent tests: src/router.test.ts, src/middleware.test.ts

Running 3 test files (skipping 8 unchanged)

If a changed file has no test_file mapping in graph.json, flag it:

⚠ src/newfile.ts has no test file. Run `/buff:test src/newfile.ts` to generate one.

Counterfeit context loading

Before generating any tests, load context from counterfeit memory to inform generation:

1. .buff/memory/graph.json — read the target file's entry: what calls this function (imported_by), what it depends on (imports_from), existing coverage gaps (coverage.untested)
2. ~/.buff/memory/corrections.json — check for past test-related corrections (entries where skill: "test"). Apply these to avoid repeating mistakes.
3. .buff/memory/learnings.json — check for project-specific test learnings (edge cases, patterns that apply to this code type)
4. ~/.buff/memory/patterns.json — check for error handling patterns (error_handling: "result-pattern" → assert on Result types) and test conventions (e.g., no mocks for DB)
5. Caller files — for each file in imported_by, Grep for import lines referencing the target module and the call sites using the exported symbols. Extract only the import lines and call-site lines — do NOT read full caller files. This reveals real-world usage patterns.

Smarter test generation

Context from counterfeit changes what tests get generated:

• Caller-informed inputs: Testing validateToken()? Graph shows it's called from middleware.ts with req.headers.authorization. Generate tests using real header formats (Bearer xyz, missing header, malformed token) instead of generic placeholder strings.

• Correction-aware approach: corrections.json has an entry saying "no mocks for repository tests"? Generate integration tests with real database calls instead of mocked ones.

• Pattern-aware assertions: patterns.json shows error_handling: "result-pattern"? Generate tests that assert on Result types (isOk(), isErr()) instead of try/catch.

• Learning-informed edge cases: learnings.json says "middleware order matters — auth before rate limiter"? Include ordering tests when generating middleware test suites.

If no counterfeit context exists (new project, empty memory), fall back to standard test generation — analyze the source file directly without caller context.

Test generation workflow

1. Counterfeit context load — read graph.json, corrections.json, learnings.json for the target file
2. Read target file — understand exports, functions, classes, error paths
3. Check graph for callers — Grep caller files (from imported_by) for import lines and call sites to understand how these functions are actually used
4. Generate tests with context — use real usage patterns from callers, known edge cases from learnings, and correction-informed approach
5. Place test file following project conventions:
   • If __tests__/ dir exists → place there
   • If *.test.ts pattern exists → colocate with source
   • If tests/ dir exists → place there
   • Default: colocate as <filename>.test.<ext>
6. Offer to run (or auto-run with --run)

Print: "Generated N tests in [filename]. Run now? [Y/n]"

Wait for user confirmation before running. Exception: if invoked with --run flag, execute immediately.

What makes a good buff test

Test behavior, not implementation:

// Good — tests what the function does
it('returns 401 when token is expired', async () => {
  const res = await handler(expiredTokenRequest)
  expect(res.status).toBe(401)
})

// Bad — tests implementation detail
it('calls validateToken function', () => {
  expect(validateToken).toHaveBeenCalled()
})

One assertion per test (usually):

• Tests with 5+ assertions are testing multiple things — split them
• Exception: related data shape assertions can group (checking multiple fields of one object)

Descriptive names:

• Format: [unit] [action/condition] [expected result]
• Example: parseDate with invalid string throws ParseError
• Example: createUser when email exists returns conflict error

No test interdependence:

• Each test runs in isolation
• No shared mutable state between tests
• Use beforeEach to reset state, not shared variables

Output format

// Vitest / Jest example
import { describe, it, expect, beforeEach } from 'vitest'
import { [exports] } from './[source-file]'

describe('[unit under test]', () => {
  beforeEach(() => {
    // reset state
  })

  it('[action] [condition] [expected]', () => {
    // arrange
    // act
    // assert
  })
})

# pytest example
import pytest
from [module] import [exports]

class Test[Unit]:
    def test_[action]_[condition]_[expected](self):
        # arrange
        # act
        # assert

Running tests

If user confirms (or --run flag is set):

# Vitest
bunx vitest run [test-file]

# Jest
npx jest [test-file]

# pytest
python -m pytest [test-file] -v

# Rust
cargo test [test-name]

# Go
go test ./... -run [TestName]

Report results inline:

Tests: 12 passed · 0 failed · 2 skipped
Coverage: [if available]

If tests fail, diagnose immediately — do not just show the error. Identify whether the test is wrong or the implementation is wrong.

Writes to counterfeit

After test generation and execution, update counterfeit memory:

• Coverage data → .buff/memory/graph.json: Set test_file mapping for the target file. Update coverage field with function count, tested count, and untested list.
• Test results → .buff/memory/learnings.json: If tests revealed edge cases or unexpected behavior, record as a learning. Example: {"learning": "validateToken silently returns null on empty string", "source": "test discovery", "applies_to": "src/auth.ts"}.
• Test patterns → ~/.buff/memory/patterns.json: If the test approach used a pattern not yet recorded (e.g., integration tests for repositories), update the architecture array with the pattern.

Graph update (post-skill)

After generating tests, update graph.json for the tested file:

1. Set test_file to the path of the generated test file
2. Grep the test file for references to each export in the source file
3. Update coverage.functions to the total number of exports
4. Update coverage.tested to the count of exports referenced in the test file
5. Update coverage.untested to the list of exports NOT referenced in the test file
6. Update updated_at timestamp

Correction detection

Watch for the user correcting test output (rejection, replacement, redirect, style correction). Follow the correction capture mechanism defined in counterfeit SKILL.md — detect signals, record to learnings.json + corrections.json, promote to patterns.json at 2+ occurrences. Use skill: "test" when writing correction entries.

Forge mode

In /buff:auto (forge), run tests automatically after code generation without asking. Report pass/fail inline and continue the loop. If tests fail in forge mode, fix them before proceeding to validation.

In forge mode, use --changed logic for minimum test set: only run tests affected by the files changed in the current forge cycle, rather than the full test suite. This keeps forge loops fast on large projects.