I was testing a Rails model to check whether a required field was passed in when a record is being created.
The test looked like this:
it { should validate_presence_of(:fired) }
and the corresponding code in the model was:
validates_presence_of :fired
The :fired parameter was a boolean value that could either be true or false. All of this looked rosy until I ran the tests.
This specific assertion failed while everything else passed. What a bummer!
I started a wild “bool” chase that took me to the migration files, resetting the database, the Rails console and finally back to the model. I narrowed down the issue to the fact that fired was a boolean value.
I tried searching for the issue but I didn’t find the answer I was looking for.
Funny enough when I searched for it recently, I found the answer immediately. I don’t know what that says about my search skills but I’m a work in progress.
After failed searching, I decided to go to the Rails codebase to see if I would find the solution there.
I searched for the validates_presence_of method in the repo and found the goose.
# If you want to validate the presence of a boolean field (where the real values
# are true and false), you will want to use
# <tt>validates_inclusion_of :field_name, in: [true, false]</tt>.
# This is due to the way Object#blank? handles boolean values:
# <tt>false.blank? # => true</tt>.
The validates_presence_of method raises an error if the value it receives is blank. It checks whether it is blank by calling .blank? on it.
In my code, when I passed false as a value, false.blank? evaluated to true so the validation failed.
The .blank? method doesn’t actually exist in Ruby but ActiveRecord uses it to check falsy values.
Armed with this knowledge, I ran to my editor and made the change to both the model and the test.
validates_inclusion_in :fired, in: [true, false]
The tests turned green.
This adventure showed me why it’s important to be comfortable digging into the source code of any tool that I use.
It was built by someone just like me and that the answer might be there in plain sight.