Ryan Weald's Blog

Mongodb Indexes With Rspec

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I recently had need to test some geospatial queries in a rails application. At first this seems like nothing out of the ordinary but there are a couple of minor details that if forgotten can result in failing tests

The main difference between geo queries and your average run of the mill query is the need for and index. Normally when a simple unit test suite is run you don’t worry about building indexes as you wont be querying large amounts of data to speed is not an issue. Besides if you are reading this you are using Rspec which means you are not too concerned with your test speed.

However, if you want to test geo queries in MongoDB you will have to ensure that your index is built or the query can not be executed. This is because geospatial queries can only be run against a special 2D index and not against the underlying data.

Now the obvious solution would be to place some code in your spec_helper file that will create the indexes. I felt like this was a bit to heavy handed since I only wanted to test the geospatial queries in 1 describe block.

So to fix the problem I choose to add a call to Mongoid::Indexes create_indexes method within my before block.

describe ".guides_nearby" do
  before(:each) do
    @guide = Factory(:guide)
    @result = Guide.guides_nearby("San Diego,United States")
  it {@result.first.should == @guide}