spec: fix false positive due to too-broad of exception handling

define and expect a specific exception, and then fix the spec so it
doesn't fail

Change-Id: I4fafd4f416f906a2d11b6ae84602c7319a116b55
Reviewed-on: https://gerrit.instructure.com/89884
Reviewed-by: Simon Williams <simon@instructure.com>
Tested-by: Jenkins
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>

Author: ccutrer

lib/dates_overridable.rb

@@ -4,6 +4,8 @@ module DatesOverridable
   attr_writer :without_overrides
   include DifferentiableAssignment
 
+  class NotOverriddenError < RuntimeError; end
+
   def self.included(base)
     base.has_many :assignment_overrides, :dependent => :destroy
     base.has_many :active_assignment_overrides, -> { where(workflow_state: 'active') }, class_name: 'AssignmentOverride'
@@ -52,7 +54,7 @@ def multiple_due_dates?
     if overridden
       !!multiple_due_dates_apply_to?(overridden_for_user)
     else
-      raise "#{self.class.name} has not been overridden"
+      raise NotOverriddenError, "#{self.class.name} has not been overridden"
     end
   end
 

spec/lib/dates_overridable_spec.rb

@@ -422,7 +422,7 @@
 
     context "when the object hasn't been overridden" do
       it "raises an exception because it doesn't have any context" do
-        expect { overridden.multiple_due_dates? }.to raise_exception
+        expect { overridable.multiple_due_dates? }.to raise_exception(DatesOverridable::NotOverriddenError)
       end
     end