Testing database-connected code

Getting GitHub actions and Tox to work well with databases takes a little extra work. This shows how to get MariaDB/MySQL working. The principles should be the same for other databases, like PostgreSQL. This project has a working example of this.

First, include MariaDB as a service by adding this under jobs in .github/workflows/commit.yml and .github/workflows/pull.yml. Note that the MYSQL_DATABASE: test does not refer to your database.

        image: mariadb:latest
            MYSQL_ROOT_PASSWORD: root
            MYSQL_DATABASE: test
            - 3306:3306
        options: \
            --health-cmd="mysqladmin ping" \
            --health-interval=10s \
            --health-timeout=5s \

Then, add a step to test the MariaDB connection. Add it before other steps so the workflow fails early.

    name: Initialize MariaDB
    run: |
        mysqladmin --host= ping

Then, add the SQL schema and rows needed for the tests to tests/resources/testdb.sql. There’s no security relevance here, so we can just use the root throughout.


Make sure the name of your test database won’t ever conflict with a real database. Otherwise, you’ll lose your database.

Then, in tox.ini, mysql to whitelist_externals. Then add this to the commands. It’s likely to be fast, so consider adding it as the first step.

mysql -e 'SOURCE tests/resources/testdb.sql;' --host= --user=root --password=root

Oddly, the -host= is important; “localhost” or leaving it as default won’t work. You may also want to execute a DROP DATABASE query as the last command, but that may not be needed.

Your SQL file might start with something like:

CREATE DATABASE myfakedatabase CHARACTER SET = 'utf8mb4' COLLATE 'utf8mb4_unicode_520_ci';
DROP USER IF EXISTS 'myfakeuser'@'localhost';
CREATE USER 'myfakedatabase'@'localhost' IDENTIFIED BY 'fakeuser123';
GRANT SELECT, INSERT, UPDATE, DELETE ON myfakedatabase.* TO 'myfakeuser'@'localhost';
USE valartest;

The SQL is executed using the root user, but your code may expect something different.