Enforce test immutability for agentic TDD workflows.

LLM coding agents routinely cheat test gates — weakening assertions, deleting failing tests, modifying config, or special-casing inputs. Research (ImpossibleBench, arxiv 2510.20270) shows frontier models exploit test cases 76% of the time when given write access, but cheating drops to near zero when tests are read-only. testwall enforces that boundary.

testwall init       # snapshot test files + compute SHA-256 checksums
testwall lock       # chmod 444 — agent can read but not modify
testwall run        # restore from snapshot, then execute tests
testwall verify     # check checksums — exit 1 on any mismatch
testwall accept     # verify + unlock + clean up snapshot

Even if an agent bypasses file permissions, testwall run restores the original tests from snapshot before executing them. testwall verify catches any tampering at the checksum level.

# Rust
cargo install testwall

# Python
pip install testwall

# Node
npm install -g testwall

# 1. Initialize — snapshots all test files matching default patterns
testwall init

# 2. Lock test files before handing off to an implementing agent
testwall lock

# 3. Agent implements... then run tests against the immutable snapshot
testwall run

# 4. If tests pass and nothing was tampered with, accept the result
testwall accept

Scan for test files, compute checksums, and store snapshots in .testwall/.

Without -p, uses built-in patterns for Python, Rust, JavaScript/TypeScript, Go, Java, and Kotlin — plus common config files like pytest.ini, jest.config.*, and .cargo/config.toml.

testwall init                              # auto-detect
testwall init -p "tests/**/*.py" -p "conftest.py"  # explicit patterns
testwall init -c "pytest -x"              # record the test command

Set all snapshotted test files to read-only (chmod 444).

Restore write permissions on test files.

Restore test files from snapshot, then execute the test runner. This is the tamper-proof execution path — even if the agent modified the working copies, the originals run.

testwall run                    # use command from init or auto-detect
testwall run -c "pytest"        # override test command
testwall run -- -x --no-header  # forward args to test runner

Compare current test file checksums against the manifest. Exits with code 1 if any file was modified or deleted.

testwall verify                 # fail on mismatch
testwall verify --report-only   # print report, always exit 0

The merge gate. Runs verification, then unlocks files and cleans up the snapshot directory. Rejects if any tampering is detected.

Show the current manifest: file count, lock state, snapshot presence, patterns, and test command.

testwall ships with patterns for common test conventions:

  You (test author)          testwall            Agent (implementer)
  ─────────────────          ────────            ───────────────────
  Write tests
          ├──── testwall init ────►
          ├──── testwall lock ────►
          │                              Agent implements code
          │                              Agent tries to edit tests → DENIED
          │                              Agent runs testwall run
          │                        ◄──── tests execute from snapshot
          │                              Tests pass
          ├──── testwall accept ──►
          │     ✓ checksums match
          │     ✓ files unlocked
          │     ✓ snapshot cleaned

• Weakened assertions (assert x > 0 → assert True)
• Deleted test cases
• Modified test config (conftest.py, jest.config.*)
• Special-cased test inputs
• Swapped test runner flags
• Any byte-level change to snapshotted files

MIT