Test data in yml file and many-to-many relationship?

Your application tests will often use data structures that consist of related model objects, which can be tedious to create programmatically in Java. Play includes a YAML parser which makes the task much simpler. Create a YAML file like the following, in the conf directory.

Play’s YAML syntax varies slightly from the standard. Each stanza must start with the name of the model class (eg Neighborhood) and can optionally be followed by an identifier in brackets (eg villalugano) so that you can reference the object elsewhere in the file. This is different to standard YAML syntax, which uses the ampersand character to indicate a reference.

Play uses SnakeYAML, which has an excellent documentation page with many examples. The YAML file can contain one-to-many, many-to-one and many-to-many relationships. These relationships must be explicity annotated in the model classes, and you must indicate which is the “owning side” of the relationship.

Note that if you are using PostgreSQL you may need to explicitly set the name of the user table with escape characters because user is a reserved word. Typically you will load the data structure defined in the YAML file as part of a unit test. But sometimes you may wish to populate the database with specific data in other circumstances, for example when your application starts for the first time.

The objects will be created in the database, and you can then access them as you would any other model object.