Add support for validation contexts

NEWS.md

@@ -1,5 +1,8 @@
 # HEAD
 
+* Support validation contexts for testing validations `on: :create` and when
+  using custom contexts like `model.valid?(:my_context)`.
+
 # v 1.5.6
 * Revert previous change in `AllowValueMatcher` that added a check for a
 properly-set attribute.

lib/shoulda/matchers/active_model/allow_value_matcher.rb

@@ -43,6 +43,11 @@ def for(attribute)
           self
         end
 
+        def on(context)
+          @context = context
+          self
+        end
+
         def with_message(message)
           self.options[:expected_message] = message
           self
@@ -78,7 +83,7 @@ def description
         private
 
         attr_accessor :values_to_match, :message_finder_factory,
-          :instance, :attribute, :value, :matched_error
+          :instance, :attribute, :context, :value, :matched_error
 
         def errors_match?
           has_messages? && errors_for_attribute_match?
@@ -161,7 +166,7 @@ def model_name
         end
 
         def message_finder
-          message_finder_factory.new(instance, attribute)
+          message_finder_factory.new(instance, attribute, context)
         end
       end
     end

lib/shoulda/matchers/active_model/exception_message_finder.rb

@@ -3,9 +3,10 @@ module Matchers
     module ActiveModel
       # Finds message information from exceptions thrown by #valid?
       class ExceptionMessageFinder
-        def initialize(instance, attribute)
+        def initialize(instance, attribute, context=nil)
           @instance = instance
           @attribute = attribute
+          @context = context
         end
 
         def allow_description(allowed_values)
@@ -39,7 +40,7 @@ def expected_message_from(attribute_message)
         private
 
         def validate_and_rescue
-          @instance.valid?
+          @instance.valid?(@context)
           []
         rescue ::ActiveModel::StrictValidationFailed => exception
           [exception.message]

lib/shoulda/matchers/active_model/validation_matcher.rb

@@ -9,6 +9,11 @@ def initialize(attribute)
           @strict = false
         end
 
+        def on(context)
+          @context = context
+          self
+        end
+
         def strict
           @strict = true
           self

lib/shoulda/matchers/active_model/validation_message_finder.rb

@@ -6,9 +6,10 @@ module ActiveModel
       class ValidationMessageFinder
         include Helpers
 
-        def initialize(instance, attribute)
+        def initialize(instance, attribute, context=nil)
           @instance = instance
           @attribute = attribute
+          @context = context
         end
 
         def allow_description(allowed_values)
@@ -58,7 +59,7 @@ def validated_instance
         end
 
         def validate_instance
-          @instance.valid?
+          @instance.valid?(@context)
           @instance
         end
       end

spec/shoulda/matchers/active_model/allow_value_matcher_spec.rb

@@ -56,6 +56,24 @@
     end
   end
 
+  context "an attribute with a context-dependent validation" do
+    context "without the validation context" do
+      it "allows a bad value" do
+        validating_format(:with => /abc/, :on => :customisable).should allow_value("xyz").for(:attr)
+      end
+    end
+
+    context "with the validation context" do
+      it "allows a good value" do
+        validating_format(:with => /abc/, :on => :customisable).should allow_value("abcde").for(:attr).on(:customisable)
+      end
+
+      it "rejects a bad value" do
+        validating_format(:with => /abc/, :on => :customisable).should_not allow_value("xyz").for(:attr).on(:customisable)
+      end
+    end
+  end
+
   context 'an attribute with several validations' do
     let(:model) do
       define_model :example, :attr => :string do