Information about the differential fuzzer tool, how to run it and use it catch bugs in Turso. Always load this skill when running this tool
Always load Debugging skill for reference
The differential fuzzer compares Turso results against SQLite for generated SQL statements to find correctness bugs.
testing/differential-oracle/fuzzer/
# Basic run (100 statements, random seed)
cargo run --bin differential_fuzzer
# With specific seed for reproducibility
cargo run --bin differential_fuzzer -- --seed 12345
# More statements with verbose output
cargo run --bin differential_fuzzer -- -n 1000 --verbose
# Keep database files after run (for debugging)
cargo run --bin differential_fuzzer -- --seed 12345 --keep-files
# All options
cargo run --bin differential_fuzzer -- \
--seed <SEED> # Deterministic seed
-n <NUM> # Number of statements (default: 100)
-t <NUM> # Number of tables (default: 2)
-c <NUM> # Columns per table (default: 5)
--verbose # Print each SQL statement
--keep-files # Persist .db files to disk
# Run forever with random seeds
cargo run --bin differential_fuzzer -- loop
# Run 50 iterations
cargo run --bin differential_fuzzer -- loop 50
# Build and run from repo root
docker build -f testing/differential-oracle/fuzzer/docker-runner/Dockerfile -t fuzzer .
docker run -e GITHUB_TOKEN=xxx -e SLACK_WEBHOOK_URL=xxx fuzzer
Environment variables for docker-runner:
TIME_LIMIT_MINUTES - Total runtime (default: 1440 = 24h)PER_RUN_TIMEOUT_SECONDS - Per-run timeout (default: 1200 = 20min)NUM_STATEMENTS - Statements per run (default: 1000)LOG_TO_STDOUT - Print fuzzer output (default: false)GITHUB_TOKEN - For auto-filing issuesSLACK_WEBHOOK_URL - For notificationsAll output goes to simulator-output/ directory:
| File | Description |
|---|---|
test.sql | All executed SQL statements. Failed statements prefixed with -- FAILED:, errors with -- ERROR: |
schema.json | Database schema at end of run (or at failure) |
test.db | Turso database file (only with --keep-files) |
test-sqlite.db | SQLite database file (only with --keep-files) |
Always follow these steps
Find the seed in the error output:
INFO: Starting differential_fuzzer with config: SimConfig { seed: 12345, ... }
Re-run with that seed:
cargo run --bin differential_fuzzer -- --seed 12345 --verbose --keep-files
Check output files:
simulator-output/test.sql - Find the failing statement (look for -- FAILED:)simulator-output/schema.json - Check table structure at failure timeCreate a minimal reproducer
.sqltest or in .rs always load Debugging skill for referenceCompare behavior manually: If needed try to compare the behaviour and produce a report in the end. Always write to a tmp file first with Edit tool to test the sql and then pass it to the binaries.
# Run failing SQL against SQLite
sqlite3 :memory: < simulator-output/test.sql
# Run against tursodb CLI
tursodb :memory: < simulator-output/test.sql
| File | Purpose |
|---|---|
main.rs | CLI parsing, entry point |
runner.rs | Main simulation loop, executes statements on both DBs |
oracle.rs | Compares Turso vs SQLite results |
schema.rs | Introspects schema from both databases |
memory/ | In-memory IO for deterministic simulation |
Set RUST_LOG for more detailed output:
RUST_LOG=debug cargo run --bin differential_fuzzer -- --seed 12345