Asserts in Rails from models or controllers?

Question

Is there a built-in way of specifying asserts in Rails that will throw an exception if an invariant is broken during development and testing?

Edit: Just to be clear, I'm looking for asserts that can be placed in models or controllers as opposed to asserts that you would use for unit tests.

Answer 1

There are many assert functions if you are writing tests. But for assertiona in the main code, there aren't any and you can roll your own easily.

Add something like this to environment.rb:

class AssertFailure < Exception
end

def assert(message = 'assertion failed')
  unless block_given? and yield
    raise message
  end
end

and make it a no-op in your environments/production.rb so there is minimal overhead

def assert(message = 'assertion failed')
end

Then, in your code, you can assert to your heart's content:

assert { value == expected_value }
assert('value was not what was expected') { value == expected_value }

If value does not equal expected_value and you aren't running in production, an exception will be raised.