Unit Testing And Starting MongoDb Server

Question

I am running some unit test that persist documents into the MongoDb database. For this unit test to succeed the MongoDb server must be started. I perform this by using Process.Start("mongod.exe").

It works but sometimes it takes time to start and before it even starts the unit test tries to run and FAILS. Unit test fails and complains that the mongodb server is not running.

What to do in such situation?

Answer 1

Can't you run a quick test query in a loop with a delay after launching and verify the DB is up before continuing?

Answer 2

If you use external resource(DB, web server, FTP, Backup device, server cluster) in test then it rather integration test then unit test. It is not convenient and not practical to start that all external resources in test. Just ensure that your test will be running in predictable environment. There are several ways to do it:

1. Run test suite from script (BAT, nant, WSC), which starts MongoDB before running test.
2. Start MongoDB on server and never shut down it.

Do not add any loops with delays in your tests to wait while external resource is started - it makes tests slow, erratic and very complex.

Answer 3

I guess I'd (and by that I mean, this is what I've done, but there's every chance someone has a better idea) write some kind of MongoTestHelper that can do a number of things during the various stages of your tests.

Before the test run, it checks that a test mongod instance is running and, if not, boots one up on your favourite test-mongo port. I find it's not actually that costly to just try and boot up a new mongod instance and let it fail as that port is already in use. However, this very different on windows, so you might want to check that the port is open or something.

Before each individual test, you can remove all the items from all the tested collections, if this is the kind of thing you need. In fact, I just drop all the DBs, as the lovely mongodb will recreate them for you:

for (String name : mongo.getDatabaseNames()) {  
  mongo.dropDatabase(name);
}

After the tests have run you could always shut it down if you've chosen to boot up on a random port, but that seems a bit silly. Life's too short.

Answer 4

It's actually easier :)... just run mongodb as a service:
http://stackoverflow.com/questions/2438055/how-to-run-mongodb-as-windows-service

It's super easy except on some OS's you have fiddle with some Registry settings to get the service to start, you can search and find article about this fiddling. Let me know if you need any help.