The other day I was writing a Rails controller test on a controller that was using a hash of the parameters. My controller tests were failing when they shouldn't have been and I was so confused. Eventually, I realized that's because my test setup was defining the params hash with the keys as strings, but my controller was accessing the key it needed with a symbol. Ahh!

Then I learned that in the actual controller when the program is running, it didn't actually matter if I accessed the key with a symbol or a string, because controller parameters in Rails act like a Hash With Indifferent Access (and in fact, if you call to_h on a params object, you'll get a hash with indifferent access back).

So, if I want the same behavior in my test, where I am mocking the parameters I need as a hash instead of a real parameters object, I should be sure to call with_indifferent_access on the hash so that it doesn't matter whether my controller uses a symbol or string for the key.