Background: We have a dependency on an externally managed database. This is a company-wide resource. We have a read-only account into it and have no control over or input into the schema or contents.
Issue: We're using ActiveRecord as our ORM into said resource; we manage the connection information separate from our central db connection information. It worked out fine. We have some characterization tests that verify that our ActiveRecords retrieve the data for a few know datapoints. However, we have no test/dev environment replacement strategy for this database. Right now all of our environments are configured to use the production database connection:
- That sucks
- We don't want the production password on the build server, so our build is broken
- The queries to the production database server are slow and because caching is off in test/dev our homepage loads REALLY slow locally
So we need something else in test/dev mode.
Q) Why not just have another sqlite database locally that mimics the schema of the production database?
A) Because we've tried that for another connection and it's lousy for at least a couple reasons.
- It's fairly complex managing the separate schema (sqlite db file) in the rake process just for testing/dev.
- Testing ActiveRecords outside of a schema that's managed by some process that ensures schema consistency between environments is largely meaningless.
- The database configuration doesn't feel like the right seam. The database connection aspect of this, and thus the AR, is not part of what we're developing, it's just a connection library in this case. As long as we can ensure our test/dev replacement for it acts the same as the production AR, then it doesn't matter if we use AR for this in test/dev. I hope that made sense, it's an important point.
Q) You could use SchemaDumper to grab the schema of the production database and use it to generate the test database. That way all the SQLy details would be automated and it would look more like typical rails stuff.
A) Yeah, that would be pretty hot, but SchemaDumper doesn't seem to play nicely with the production database connection. It just hangs after a while and we don't get the whole schema. Bummer. That also doesn't avoid having to manage that whole other database file and work managing said file into our rake tasks.
What I really want to do is to have production use the ARs that are tested in the characterization tests and then have another object that's a plain old PORO that reads stuff out of a yaml file (like a fixture) that replaces the object in the test/development/build environments.
Q) But Najati, isn't putting that stuff in a yaml file the same as defining the schema?
A) Well, yeah, sorta. Its just a lot more direct and easier to manage if it's in some PORO that loads some crap out of a yamlfile than if I also have to work some half-baked schema management into our build tasks; we do this currently and it's pretty lousy and, frankly, doesn't seem to be buying us much. Also the test schema and the test data fixture duplication the information: "this is what we want the test version of this data to look like" - why do we need both? I claim "So that you can use the same AR in both environments." is not a sufficient argument to justify the complexity of managing the extra sqlite db file.
Q) I feel like there's something you're not telling me.
A) I've been cheating on my Weight Watchers. Also,
In the past when I've had something like this my solution looked like this:
- Characterization tests that capture the important aspects of the external service's behavior, run not with the unit test suite, but as a separate process on the build server, maybe once every 4 hours or every night or whatever.
- A fake implementation that used the same set of tests to exercise it's behavior to ensure that it was providing similar functionality to the test/dev environment.
Spring (and probably dependency injection containers in general) makes this easy. You just swap out beans in your environment-specific bean config and the test env just goes on it's merry way.
Given my understanding/knowledge, Rails doesn't seem to be lending itself to this very well. I supposed I could redefine the class in my test/dev environment scripts, but that seems really shady. For one thing, I don't know if that would keep the model from being loaded at application start-up, and another, that would add yet another strange wrinkle to our Rails project, another bit of magic that would make the project harder to come up to speed on. I want something that feels like the "service replacement" strategy used in Spring that doesn't require hard-to-find/understand RoR magic.
Uhh. I'll stop there and see if that much prompts anything. Thanks for taking the time to read!