Weasel

Weasel is a library for low level database development with PostgreSQL, SQL Server, Oracle, MySQL, SQLite and Firebird. Weasel is in the process of being extracted from Marten with the goal of making this code reusable in other projects.

Read also more in Introducing Weasel for Database Development by Jeremy D. Miller.

You can acccess the docs here.

Branch Strategy

Branch	Version line	Purpose
master	9.0 (Critter Stack 2026)	Active development. All new work targets this branch.
8.0	8.x	Maintenance only — critical fixes for the 8.x line.

Weasel 9.0 is part of the Critter Stack 2026 release wave, shipping in lockstep with JasperFx 2.0, JasperFx.Events 2.0, Marten 9.0, and Polecat 4.0. See the 9.0 master plan and the migration guide for upgrade details.

Documentation

The docs site is VitePress. Its dependencies live in the root package.json — there is no separate tree under docs/, and docs/package.json is only the marker that makes Node treat docs/.vitepress/config.ts as ESM.

npm ci
npm run docs          # dev server on port 5050
npm run docs-build    # production build, as publish-docs.yml runs it

Both scripts run mdsnippets first, so code samples are pulled from the compilable test projects rather than written into the Markdown by hand.

Support Plans

While Weasel is open source, JasperFx Software offers paid support and consulting contracts for Weasel.

Key Components

• Core: Foundational interfaces and base classes for database interactions.
• Postgresql: Types and classes specific to PostgreSQL database features.
• SqlServer: Types and classes specific to SQL Server database features.
• Schema: Tools for managing database schema.

Usage

Setting up databases locally

To run tests, you need to set up databases locally. The easiest option is to do it by running Docker images. You can use predefined Docker Compose setup by calling in your terminal:

docker compose up

It'll spin up PostgreSQL and MSSQL databases.

Then, you can run tests from the terminal:

dotnet test

Or your favourite IDE.

Test Config Customization

Some of our tests are run against a particular PostgreSQL version. If you'd like to run different database versions, you can do it by setting POSTGRES_IMAGE or MSSQL_IMAGE env variables, for instance:

POSTGRES_IMAGE=postgres:15.3-alpine MSSQL_IMAGE=mcr.microsoft.com/mssql/server:2022-latest docker compose up

Support Plans

While Weasel is open source, JasperFx Software offers paid support and consulting contracts for Weasel.