rspec: model.should be_valid

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rspec: model.should be_valid

One of the things I always check when spec’ing is that the model that I just created is valid.

@mymodel.should be_valid

This uses RSpec’s predicate support (any call to be_something? calls something? on the target object), and returns a correct but very unhelpful error:

expected valid? to return true, got false

Here is a little rspec matcher that I threw together this morning to check if a model is valid and spit out the validation errors:

module Spec
  module Rails
    module Matchers
      class BeValid  #:nodoc:

        def matches?(model)
          @model = model
          @model.valid?
        end

        def failure_message
          "#{@model.class} expected to be valid but had errors:\n  #{@model.errors.full_messages.join("\n  ")}"
        end

        def negative_failure_message
          "#{@model.class} expected to have errors, but it did not"
        end

        def description
          "be valid"
        end

      end

      def be_valid
        BeValid.new
      end
    end
  end
end

Now, I get:

MyModel expected to be valid but had errors:
  Password confirmation can't be blank
  Email has already been taken

This is nothing fancy, but it’s the small stuff that make life meaningful, so I thought I would share it. Throw the matcher code above into your spec_helper and check if your models are valid.

update: added negative_failure_message so “model.should_not be_valid” will work

Code: rspec, ruby, testing Apr 18, 2007 ● updated Sep 25, 2007 ● 8 comments

8 comments

Perfect use of custom matchers! Nice.

Cheers, David

David Chelimsky April 19, 2007 at 09:40 AM
Ah… that’s how be_valid works. Newly generated model specs use the be_valid method, but I couldn’t find any documentation for it. Thanks for the heads up!

Rabbit August 01, 2007 at 06:50 PM
I threw this into spec/spec_helper.rb; is that the right place, or is there a better place to put this?
Also, it wouldn’t work with should_not be_valid. I had to add this:
```
  def negative_failure_message
    "#{@model.class} expected to be invalid but was valid.\n" 
  end
```
Other than that, it’s been a great help in finding the source of problems when the results are not as I was expecting.
Craig Buchek August 05, 2007 at 08:45 PM
Would be nice to see this as part of the rspec rails plugin. Did you already submit a patch for it?

Hans de Graaff November 06, 2007 at 03:23 PM
Thanks for the addition. Much appreciated.

Bryan Ray December 08, 2007 at 12:42 PM
nice one

Gustav Paul January 11, 2008 at 02:36 PM
thanks

Edwin Moss April 28, 2008 at 05:08 PM
thanks! this is great!

ttsuchi October 09, 2008 at 10:35 PM

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