Aqueduct & in memory database

Question

just wanted to know, if the Aqueduct ORM supports a simple in memory database, for testing purposes. Looking for something easy and lightweight to write the backend, before actually connecting it to postgres.

Answer 1

I've used similar approach with H2 and Postgres with Java, but it is rather error-prone: While the SQL interface may be similar, you could be using a feature that is available in one, but not the other. Eventually, either your development is blocked, or it is OK, but then the real deployment will be hitting issues.

I've found that starting a Postgresql instance in a docker is much easier than I've first thought, and now I use the same principle for most external dependencies: run them inside docker. If there is an interest, I can open source a Dart package that starts the docker container and waits until a certain string pattern is present on the output (e.g. a report on successful start).

Answer 2

Aqueduct was built to be tested with a locally running instance of PostgreSQL. This avoids the class of errors that occur when using a different database engine in tests vs. deployment. It is a very important feature of Aqueduct.

The tl;dr is that you can use a local instance of PostgreSQL with the same efficiency as an in-memory database and there is documentation on the one-time setup process.

The Details

Aqueduct creates an intermediate representation of your data model at startup by reflecting on your application code. This representation drives database migrations, serialization, runtime reflection, and can even be exported as JSON to create data modeling tools on top of Aqueduct.

At the beginning of each test suite, your test harness uses this representation to generate temporary tables in a local database named dart_test. Temporary tables are destroyed as soon as the database connection is lost; which you can configure to happen between tests, groups of tests, or entire test suites depending on your needs. It turns out that this is very fast - on the order of milliseconds.

CI platforms like TravisCI and Appveyor both support local PostgreSQL processes. See this script and this travis config for an example.