clone a postgresql database for testing cleanly | Down Home Country Coding With Scott Selikoff and Jeanne Boyarsky (original) (raw)

I’m looking at writing integration tests for the back end of JavaRanch‘s JForum install.

A few “pesky” requirements/constraints

• Multiple developers all over the word have their own local test databases filled with data in different states. The tests must work for everyone. Ideally they won’t leave data floating around either.
• The tests must use PostgreSQL. While the original JForum supported multiple databases, the JavaRanch version has been scaled down to just run with the one we need. We do have some PostgreSQL specific SQL which rules out using an embedded database like HSQLDB or Derby.
• Developers are using both Eclipse and IntelliJ. Tests should care about the IDE anyway, so this isn’t a big constraint.
• Developers are using a variety of operating systems and languages on their operating systems. While code is in English, there can’t be assumptions as to the OS state.

Strategy

I think the best strategy is to create a second database just for testing. The JForum database would remain untouched and a jforum_integration_test database can be created for the tests. dbUnit can control the state of that special database.

The problem

Before I even start thinking about dbUnit, I did a proof of concept to ensure I could create a new database from scratch using the command line. Creating a database is the easy part. The “hard” part is that JForum doesn’t come with a schema. It comes with an installation servlet that creates the schema. While few people will be creating a schema for JForum, the technique I used applies elsewhere.

The procedure “before”

1. Start up the JForum war
2. Go to the JForum install URL and enter some information which creates the tables
3. Run the JavaRanch customizations.

How to clone a database for which you only have a partial script

1. Create an empty database
   createdb jforum_integration_test
2. Arrive at the base schema
   1. Go the JForum installation URL
   2. Enter the information to create the tables
3. Export the schema thus far
   pg_dump -U postgres jforum_integration_test > c:\temp\postgres.sql
4. Provide instructions for the rest of the sql which were created by our developers.

How to import

Now for the easy part!

Importing this dump is a matter of a single command:

psql -U postgres jforum < "pathToWorkspace\JForum\javaranch-docs\deployment\file.ddl"

Lessons learned after

The next day I learned that this wasn’t enough. We also needed some test data from the server. I ran this a few times to get the relevant test data.

pg_dump --data-only --inserts -U user -W database --file roles --table tableName
Conclusion

My next step will be to actually configure dbUnit against this new database and start writing tests.