Question

I am running mysql, database_cleaner, Rspec, etc. I have about 518 tests so far and they take 88 seconds to run. This is unacceptable to me as my app development is just beginning.

So before going further, I’d like to try and find ways to reduce the time it takes to run these tests – hopefully without having to actually change the tests.

In most cases, I am trying to use stubs. However, when I am testing models and queries, I do use the database.

I think database_cleaner is slowing them down, but I don’t know how to test queries and stuff without it.

Using sqlite3 with the “:memory:” option only seems to shave off about 10 seconds (kind of disappointing result…)

What can I do to really speed up my tests?

Answer 1

Ryan Brunner offered a lot of great advice. Everything he said is true in general, yet did not apply to me.

I didn’t mention Factory Girl because I didn’t think to mention it (don’t ask). It turned out to be very relevant detail because it was responsible for the tests running so slow.

By simply removing Factory girl completely from my controller tests (I was using Factory.build), I have managed to get them down from 50 seconds to something like 5.

The reason is that Factory.build calls Factory.create for associations, which causes a database hit… so if you have a lot of associations, it will take awhile to create a new model object. But even more, that only accounted for 30-35% of the overhead in my case. Factory_girl was actually spending 65-70% of its time doing non-database stuff. I have no idea why, but after forcing every call to be Factory.build, it will still taking quite awhile to build my objects. Going with basic MyClass.new ended up being MUCH faster.

My entire test suite now takes a little under 30 seconds instead of up to 90 seconds. That is a 300% speed increase in general by making these changes… but when it came to the controller tests, I got a 2000% speed increase – and I was already stubbing! All of that performance overhead was due to Factory.build! That is where most of the gains came from.

Of course, I went back into my models and used Factory.build or simply MyClass.new wherever I could.

I also added :default_strategy => :build in factories.rb too whenever I could, to prevent Factory Girl from hitting the database. If you ask me, this should be the default as only 1 test failed as a result of this change, but I managed to get 10 entire seconds out of my model tests by this change alone.

If you’re having problems like I am, follow these steps and you should notice a 2-3x speed improvement with not much drawback.