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| 1 | +# Uncle Bob's AI Coding Style |
| 2 | + |
| 3 | +Use evidence-first development: surround the implementation with an executable |
| 4 | +specification and a gauntlet of constraints so confidence comes from auditable |
| 5 | +evidence instead of line-by-line review. |
| 6 | + |
| 7 | +The trust model has two primary artifacts: an executable specification approved |
| 8 | +before implementation, and an evidence report produced after real verification. |
| 9 | +The gauntlet proves only the constraints expressed by the specification, so be |
| 10 | +explicit about assumptions, invariants, skipped checks, and remaining risk. |
| 11 | + |
| 12 | +## Diagnostics-first constraint |
| 13 | + |
| 14 | +Before editing, record a diagnostics baseline by calling the |
| 15 | +`diagnostics_baseline` MCP tool. After each edit, call the `get_diagnostics` MCP |
| 16 | +tool with `since="baseline"` for every touched file. Do not finish until its |
| 17 | +status is `clean`, meaning no new diagnostics versus the baseline. |
| 18 | + |
| 19 | +## Required loop |
| 20 | + |
| 21 | +SPEC → (human approves spec, not code) → RED → GREEN → REFACTOR → GAUNTLET → EVIDENCE |
| 22 | + |
| 23 | +Repeat RED through REFACTOR for each behavior. Never weaken the gauntlet to make |
| 24 | +the implementation appear successful. |
| 25 | + |
| 26 | +### 1. SPEC |
| 27 | + |
| 28 | +Before changing implementation files, turn the request into executable |
| 29 | +acceptance criteria: |
| 30 | + |
| 31 | +- Describe concrete inputs, outputs, edge cases, and error cases as Gherkin |
| 32 | + scenarios or a named test list. |
| 33 | +- Include negative constraints: existing behavior, public APIs, data integrity, |
| 34 | + performance budgets, and anything else that must not change. |
| 35 | +- Include the setup plan: tools to install, files to add, git/checkpoint usage, |
| 36 | + and every new dependency with a one-line justification. |
| 37 | +- Show the specification to the human and obtain approval before implementation. |
| 38 | + In autonomous mode, proceed only if allowed, and record that approval was not |
| 39 | + obtained so the final confidence claim is correspondingly weaker. |
| 40 | +- Treat the specification as append-only. If it is wrong, revise it visibly and |
| 41 | + explain why; never let implementation silently redefine it. |
| 42 | + |
| 43 | +### 2. RED |
| 44 | + |
| 45 | +Write the smallest test for one approved behavior and run it before changing the |
| 46 | +implementation. Observe the expected assertion failure. A collection or import |
| 47 | +failure is weaker evidence; create a minimal stub when needed so the failure is |
| 48 | +about behavior. If the new test already passes, use a temporary mutant to prove |
| 49 | +the test can fail, restore the source, and record the behavior as pre-existing. |
| 50 | + |
| 51 | +### 3. GREEN |
| 52 | + |
| 53 | +Write the least implementation needed to pass the failing test, then run the |
| 54 | +full suite. Do not refactor or expand the feature during Green. |
| 55 | + |
| 56 | +### 4. REFACTOR |
| 57 | + |
| 58 | +With the suite green, improve naming, cohesion, duplication, and control flow |
| 59 | +without changing behavior. Implementation refactors must not edit tests. |
| 60 | +Test-structure refactors are a separate step: keep assertions unchanged, run |
| 61 | +the suite before and after, and rerun mutation checks. Any assertion change is a |
| 62 | +behavior change and returns to SPEC. |
| 63 | + |
| 64 | +### 5. GAUNTLET |
| 65 | + |
| 66 | +Run every applicable constraint layer. Scale the effort using Calibration, but |
| 67 | +never skip a layer silently. |
| 68 | + |
| 69 | +| Layer | Constraint | |
| 70 | +|---|---| |
| 71 | +| Full test suite | Zero new failures; record any pre-existing baseline failures verbatim. | |
| 72 | +| Static types | Zero new compiler or type-checker errors. | |
| 73 | +| Lint and format | Zero new warnings or formatting drift. | |
| 74 | +| Changed-line coverage | Every changed behavior-bearing line and branch is exercised; do not chase a global percentage. | |
| 75 | +| Mutation testing | Use a mutation tool or 3-5 scripted manual mutants; every non-equivalent mutant must be killed. | |
| 76 | +| Property tests | Add invariant-based tests for parsing, math, serialization, ordering, or round trips when applicable. | |
| 77 | +| Complexity budget | Keep new functions small, cohesive, and easy to explain. | |
| 78 | +| Real execution | Run the application, CLI, or endpoint once with realistic input. | |
| 79 | +| Supply chain and secrets | Audit dependency changes, licenses, secrets, and newly introduced capabilities. | |
| 80 | +| Suite health | Check determinism, randomized order where supported, and suspected flakes. | |
| 81 | + |
| 82 | +Mutation kills validate the suite as a whole unless a layer is run separately. |
| 83 | +Classify tool-generated equivalent mutants honestly. Hand-written mutants must |
| 84 | +represent real bugs and receive no equivalent-mutant exemption. |
| 85 | + |
| 86 | +### 6. EVIDENCE |
| 87 | + |
| 88 | +Finish with a reproducible report containing: |
| 89 | + |
| 90 | +- The approved specification and a scenario-to-test mapping. |
| 91 | +- Every gauntlet command and its actual numeric result from one fresh run after |
| 92 | + the final edit. |
| 93 | +- A single persisted entry-point command that reruns every applicable layer, |
| 94 | + with tool versions pinned or recorded. |
| 95 | +- The source state, using a commit SHA or a reproducible tree hash. |
| 96 | +- Every skipped layer and the reason. |
| 97 | +- Failures encountered and how they were resolved. |
| 98 | +- Remaining risks and limits, without claiming absolute proof. |
| 99 | + |
| 100 | +## Anti-gaming rules |
| 101 | + |
| 102 | +1. Never weaken, skip, broaden, or delete a test to make it pass. |
| 103 | +2. Never edit a test and its implementation in the same step on the path to |
| 104 | + Green. Change one, run it, then change the other. |
| 105 | +3. Never mock the unit under test. Mock only true boundaries such as network, |
| 106 | + clock, filesystem, or process execution. |
| 107 | +4. Never add vacuous tests merely to raise coverage. |
| 108 | +5. Never report a layer that was not run. |
| 109 | +6. A failing applicable gauntlet layer blocks completion. If blocked, report the |
| 110 | + exact failure instead of weakening the constraint. |
| 111 | + |
| 112 | +## Calibration |
| 113 | + |
| 114 | +- Tier 1, trivial: full suite plus lint. Explain why a new test is unnecessary |
| 115 | + or why existing coverage is sufficient. |
| 116 | +- Tier 2, normal feature or bug fix: the full SPEC, RED, GREEN, REFACTOR, |
| 117 | + GAUNTLET, EVIDENCE loop. Bug fixes start with a regression test. |
| 118 | +- Tier 3, high stakes: first write a failure model for risks such as money, |
| 119 | + authentication, data loss, concurrency, migrations, public API compatibility, |
| 120 | + unbounded growth, or silent production failure. Add targeted stress, fuzz, |
| 121 | + rollback, contract, observability, compatibility, or benchmark layers. Also |
| 122 | + require property tests, mutation testing, and an adversarial pass. |
| 123 | + |
| 124 | +## Setup rules |
| 125 | + |
| 126 | +Prefer the repository's current tools. If essential tooling is missing, put its |
| 127 | +installation and every environment change in the approved SPEC. Prefer standard |
| 128 | +libraries and existing dependencies. Do not initialize git, install packages, or |
| 129 | +create checkpoint commits without authorization. If tooling is declined or |
| 130 | +unavailable, use the best manual layer and record the reduced confidence. |
| 131 | + |
| 132 | +# Gauntlet Tooling by Ecosystem |
| 133 | + |
| 134 | +Use project-native commands when they exist. The following are defaults only. |
| 135 | + |
| 136 | +## Python |
| 137 | + |
| 138 | +| Layer | Default | |
| 139 | +|---|---| |
| 140 | +| Tests | `pytest -q` | |
| 141 | +| Types | `mypy <pkg>` or pyright | |
| 142 | +| Lint and format | `ruff check .` and `ruff format --check .` | |
| 143 | +| Coverage | pytest-cov with branch coverage; use diff-cover when configured | |
| 144 | +| Mutation | mutmut scoped to changed modules | |
| 145 | +| Property tests | hypothesis | |
| 146 | + |
| 147 | +## JavaScript and TypeScript |
| 148 | + |
| 149 | +| Layer | Default | |
| 150 | +|---|---| |
| 151 | +| Tests | `npx vitest run` or `npx jest` | |
| 152 | +| Types | `npx tsc --noEmit` | |
| 153 | +| Lint | `npx eslint .` | |
| 154 | +| Coverage | Vitest or Jest coverage, checked against changed lines | |
| 155 | +| Mutation | Stryker scoped to changed files | |
| 156 | +| Property tests | fast-check | |
| 157 | + |
| 158 | +## Go |
| 159 | + |
| 160 | +| Layer | Default | |
| 161 | +|---|---| |
| 162 | +| Tests | `go test ./... -race` | |
| 163 | +| Types and build | `go build ./...` | |
| 164 | +| Lint | `go vet ./...` and staticcheck | |
| 165 | +| Coverage | `go test -coverprofile=c.out ./...` then `go tool cover -func=c.out` | |
| 166 | +| Mutation | scripted manual mutation | |
| 167 | +| Property tests | testing/quick or rapid | |
| 168 | + |
| 169 | +## Rust |
| 170 | + |
| 171 | +| Layer | Default | |
| 172 | +|---|---| |
| 173 | +| Tests | `cargo test` | |
| 174 | +| Types | `cargo check` | |
| 175 | +| Lint | `cargo clippy -- -D warnings` | |
| 176 | +| Coverage | cargo-llvm-cov with branch coverage | |
| 177 | +| Mutation | cargo-mutants scoped to changed files | |
| 178 | +| Property tests | proptest | |
| 179 | + |
| 180 | +## Extended layer menu |
| 181 | + |
| 182 | +Select additional layers from the failure model: |
| 183 | + |
| 184 | +- Dependency and license audit whenever dependencies change. |
| 185 | +- Secret scan and a manual capability diff for new network, subprocess, |
| 186 | + filesystem, or environment access. |
| 187 | +- Randomized test order and repeated runs for suite-health concerns. |
| 188 | +- API compatibility checks when a public API changes. |
| 189 | +- Race detectors and stress tests for concurrency. |
| 190 | +- Benchmarks only when the SPEC states a measurable performance budget. |
| 191 | +- Accessibility, screenshot, and browser checks for user-facing UI. |
| 192 | +- Version-matrix checks when the project claims multiple supported versions. |
| 193 | +- Log or metric assertions when silent production failure is a risk. |
| 194 | + |
| 195 | +## Manual mutation procedure |
| 196 | + |
| 197 | +When no mutation tool is available, persist a repository script that saves the |
| 198 | +original source, applies one plausible bug at a time, runs the relevant suite, |
| 199 | +and restores the source. Use 3-5 mutants such as a flipped comparison, off-by-one |
| 200 | +bound, removed branch, swapped boolean operator, or constant return. Every mutant |
| 201 | +must fail at least one test. Verify restoration with the final diff and suite, |
| 202 | +then report `manual mutation: N/N killed`. |
| 203 | + |
| 204 | +## Reproducible gauntlet entry point |
| 205 | + |
| 206 | +Persist one command that removes stale artifacts, runs every applicable layer in |
| 207 | +sequence, and fails on the first broken layer. Pin or record development-tool |
| 208 | +versions. The final evidence numbers must come from one fresh execution of this |
| 209 | +entry point after the last edit. |
| 210 | + |
| 211 | +## Executable specification template |
| 212 | + |
| 213 | +```gherkin |
| 214 | +Feature: <capability in user language> |
| 215 | + Scenario: <one concrete behavior> |
| 216 | + Given <concrete starting state> |
| 217 | + When <concrete action with concrete input> |
| 218 | + Then <concrete observable outcome> |
| 219 | +
|
| 220 | + Scenario: <error or invariant case> |
| 221 | + Given <concrete starting state> |
| 222 | + When <invalid, hostile, or boundary input> |
| 223 | + Then <exact error and state that must not change> |
| 224 | +``` |
| 225 | + |
| 226 | +## Evidence report template |
| 227 | + |
| 228 | +```markdown |
| 229 | +## Evidence Report — <task name> (Tier <1|2|3>) |
| 230 | + |
| 231 | +- Spec approval: <obtained | not obtained, confidence downgraded> |
| 232 | +- Source state: <commit SHA | reproducible tree hash> |
| 233 | +- Toolchain: <versions file or recorded versions> |
| 234 | +- Entry point: <one command that reruns the gauntlet> |
| 235 | + |
| 236 | +### Spec to test mapping |
| 237 | +| Scenario or invariant | Test or layer | Status | |
| 238 | +|---|---|---| |
| 239 | +| <behavior> | <test name> | pass, fail, unverified, or n-a | |
| 240 | + |
| 241 | +### Fresh gauntlet results |
| 242 | +| Layer | Command | Numeric result | |
| 243 | +|---|---|---| |
| 244 | +| Tests | <command> | <passed and failed counts> | |
| 245 | +| Types | <command> | <error count> | |
| 246 | +| Lint | <command> | <warning count> | |
| 247 | +| Changed-line coverage | <command> | <covered/total> | |
| 248 | +| Mutation | <command> | <killed/total> | |
| 249 | +| Real execution | <command> | <observed result> | |
| 250 | + |
| 251 | +### Skipped layers and honest notes |
| 252 | +- <layer>: <reason> |
| 253 | +- <failures, fixes, and remaining risks> |
| 254 | +``` |
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