SecantusDB 0.2.0a1

A surrogate single-node MongoDB server in Python for testing pymongo applications without running a real mongod.

SecantusDB

[!WARNING] Alpha software — not for production use.

SecantusDB is in early development. The API surface and on-disk format can change between point releases. It exists today as a developer tool for exercising application code against a MongoDB-shaped surrogate; it is not a database for storing data you can't recreate.

A surrogate single-node MongoDB server in Python. SecantusDB speaks the subset of the MongoDB wire protocol that pymongo emits, so test suites can talk to it instead of standing up a real mongod. No binary to install, no port conflicts, parallel-test friendly. Single-node only — replica sets and sharding are out of scope by design.

from pymongo import MongoClient
from secantus import SecantusDBServer

with SecantusDBServer(port=0) as server:
    client = MongoClient(server.uri)
    db = client["mydb"]
    db["users"].insert_one({"_id": 1, "name": "Joe"})
    assert db["users"].find_one({"_id": 1})["name"] == "Joe"

What's in scope

The subset of MongoDB that pymongo actually drives — connection handshake, CRUD, cursors, aggregation, findAndModify — backed by a real query planner with index acceleration (single-field, compound, mixed-direction, partial, TTL, sort), proper explain output (IXSCAN vs COLLSCAN), and a hash-join $lookup.

What's out of scope: replica sets, sharding, change streams, authentication, TLS, text/geo/wildcard indexes, $where, real transaction rollback. If your test depends on those, run a real mongod.

Installation

pip install SecantusDB

Pre-built wheels are published for CPython 3.12 and 3.13 on:

• macOS arm64 (Apple Silicon)
• Linux x86_64 and aarch64 (manylinux2014 / glibc, and musllinux_1_2 / Alpine)
• Windows AMD64

macOS Intel (x86_64) is not in the wheel matrix; use a from-source install if you need it.

WiredTiger is vendored inside the wheel — no separate package, no compile step, no system build tools required.

Building from source (unsupported platforms only)

If your platform isn't in the matrix above, pip install SecantusDB falls back to the sdist and compiles WiredTiger from source. That needs three native build tools on PATH:

• cmake (>= 3.21)
• ninja
• swig (>= 4.0)

Platform	Install prerequisites
macOS (Homebrew)	brew install cmake ninja swig
Debian/Ubuntu	sudo apt-get install -y cmake ninja-build swig
Fedora/RHEL	sudo dnf install -y cmake ninja-build swig
Alpine	apk add --no-cache cmake ninja swig build-base

See Installation for dev-install instructions.

Examples

A walk through the operations a typical test exercises — connect, insert, index, query, drop. Full version with explanations: examples in the docs.

from pymongo import MongoClient
from secantus import SecantusDBServer

with SecantusDBServer(port=0) as server:
    client = MongoClient(server.uri)
    cellar = client["wine_cellar"]
    bottles = cellar["bottles"]

    # --- Insert ---
    bottles.insert_one(
        {"_id": 1, "name": "Pommard 2018", "region": "Burgundy", "year": 2018}
    )
    bottles.insert_many(
        [
            {"_id": 2, "name": "Brunello 2015", "region": "Tuscany", "year": 2015},
            {"_id": 3, "name": "Barolo 2017", "region": "Piedmont", "year": 2017},
            {"_id": 4, "name": "Pommard 2020", "region": "Burgundy", "year": 2020},
        ]
    )

    # --- Indexes ---
    bottles.create_index([("year", 1)])                     # single-field
    bottles.create_index([("region", 1), ("year", -1)])     # compound

    # --- Query ---
    drinkable_now = list(
        bottles.find({"year": {"$lte": 2018}}).sort("year")
    )
    assert [b["name"] for b in drinkable_now] == [
        "Brunello 2015",
        "Barolo 2017",
        "Pommard 2018",
    ]

    by_region = list(
        bottles.aggregate(
            [
                {"$group": {"_id": "$region", "count": {"$sum": 1}}},
                {"$sort": {"_id": 1}},
            ]
        )
    )

    # --- Drop ---
    bottles.drop()                              # one collection
    client.drop_database("wine_cellar")         # whole database

Documentation

Full docs are in docs/; build them with uv run python -m invoke docs and open docs/_build/html/index.html. Highlights:

• Quickstart — embedding in tests, running standalone.
• Architecture — the layered design.
• Indexes — what find() and aggregate accelerate, explain semantics, hints, partial indexes, TTL.
• Aggregation — supported pipeline stages and expression operators.
• Compatibility — the divergences you should know about before you trust SecantusDB for a given test.

Development

git clone https://github.com/jdrumgoole/SecantusDB.git
cd SecantusDB
uv sync --extra dev
uv run python -m pytest    # 584 tests, runs in parallel under pytest-xdist

Common workflows:

uv run python -m invoke fmt    # ruff format
uv run python -m invoke lint   # ruff check
uv run python -m invoke test   # pytest, parallel
uv run python -m invoke docs   # build Sphinx docs (warnings as errors)

License

GPL-2.0-only. See LICENSE. SecantusDB intends to bundle the WiredTiger storage engine (itself GPL-2/GPL-3), so the combined work is GPL.