Adds accept_nested_attributes_for matcher

Currently supports the options "allow_destroy", "limit", and
"update_only"

lib/shoulda/matchers/active_record.rb

@@ -4,6 +4,7 @@
 require 'shoulda/matchers/active_record/have_readonly_attribute_matcher'
 require 'shoulda/matchers/active_record/serialize_matcher'
 require 'shoulda/matchers/active_record/query_the_database_matcher'
+require 'shoulda/matchers/active_record/accept_nested_attributes_for_matcher'
 
 module Shoulda
   module Matchers

lib/shoulda/matchers/active_record/accept_nested_attributes_for_matcher.rb

@@ -0,0 +1,127 @@
+module Shoulda
+  module Matchers
+    module ActiveRecord
+      # Ensures that the model can accept nested attributes for the specified
+      # association.
+      #
+      # Options:
+      # * <tt>allow_destroy</tt> - Whether or not to allow destroy
+      # * <tt>limit</tt> - Max number of nested attributes
+      # * <tt>update_only</tt> - Only allow updates
+      #
+      # Example:
+      #   it { should accept_nested_attributes_for(:friends) }
+      #   it { should accept_nested_attributes_for(:friends).
+      #                 allow_destroy(true).
+      #                 limit(4) }
+      #   it { should accept_nested_attributes_for(:friends).
+      #                 update_only(true) }
+      #
+      def accept_nested_attributes_for(name)
+        AcceptNestedAttributesForMatcher.new(name)
+      end
+
+      class AcceptNestedAttributesForMatcher
+        def initialize(name)
+          @name = name
+          self
+        end
+
+        def allow_destroy(allow_destroy)
+          @allow_destroy = allow_destroy
+          self
+        end
+
+        def limit(limit)
+          @limit = limit
+          self
+        end
+
+        def update_only(update_only)
+          @update_only = update_only
+          self
+        end
+
+        def matches?(subject)
+          @subject = subject
+          exists? &&
+            allow_destroy_correct? &&
+            limit_correct? &&
+            update_only_correct?
+        end
+
+        def failure_message
+          "Expected #{expectation} (#{@problem})"
+        end
+
+        def negative_failure_message
+          "Did not expect #{expectation}"
+        end
+
+        def description
+          description = "accepts_nested_attributes_for :#{@name}"
+          description += " allow_destroy => #{@allow_destroy}" if @allow_destroy
+          description += " limit => #{@limit}" if @limit
+          description += " update_only => #{@update_only}" if @update_only
+          description
+        end
+
+        protected
+
+        def exists?
+          if config
+            true
+          else
+            @problem = "is not declared"
+            false
+          end
+        end
+
+        def allow_destroy_correct?
+          if @allow_destroy.nil? || @allow_destroy == config[:allow_destroy]
+            true
+          else
+            @problem = (@allow_destroy ? "should" : "should not") +
+              " allow destroy"
+            false
+          end
+        end
+
+        def limit_correct?
+          if @limit.nil? || @limit == config[:limit]
+            true
+          else
+            @problem = "limit should be #@limit, got #{config[:limit]}"
+            false
+          end
+        end
+
+        def update_only_correct?
+          if @update_only.nil? || @update_only == config[:update_only]
+            true
+          else
+            @problem = (@update_only ? "should" : "should not") +
+              " be update only"
+            false
+          end
+        end
+
+        def config
+          model_config[@name]
+        end
+
+        def model_config
+          model_class.nested_attributes_options
+        end
+
+        def model_class
+          @subject.class
+        end
+
+        def expectation
+          "#{model_class.name} to accept nested attributes for #{@name}"
+        end
+      end
+    end
+  end
+end

spec/shoulda/active_record/accept_nested_attributes_for_matcher_spec.rb

@@ -0,0 +1,84 @@
+require 'spec_helper'
+
+describe Shoulda::Matchers::ActiveRecord::AcceptNestedAttributesForMatcher do
+  before do
+    define_model :child, :parent_id => :integer
+    define_model :parent do
+      has_many :children
+    end
+  end
+
+  let(:parent) { Parent.new }
+  let(:matcher) { accept_nested_attributes_for(:children) }
+
+  it "should accept an existing declaration" do
+    Parent.accepts_nested_attributes_for :children
+    matcher.matches?(parent).should be_true
+  end
+
+  it "should reject a missing declaration" do
+    matcher.matches?(parent).should be_false
+    matcher.failure_message.should == "Expected Parent to accept nested attributes for children (is not declared)"
+  end
+
+  context "allow_destroy" do
+    it "should accept a valid truthy value" do
+      Parent.accepts_nested_attributes_for :children, :allow_destroy => true
+      matcher.allow_destroy(true).matches?(parent).should be_true
+    end
+
+    it "should accept a valid falsey value" do
+      Parent.accepts_nested_attributes_for :children, :allow_destroy => false
+      matcher.allow_destroy(false).matches?(parent).should be_true
+    end
+
+    it "should reject an invalid truthy value" do
+      Parent.accepts_nested_attributes_for :children, :allow_destroy => true
+      matcher.allow_destroy(false).matches?(parent).should be_false
+      matcher.failure_message.should =~ /should not allow destroy/
+    end
+
+    it "should reject an invalid falsey value" do
+      Parent.accepts_nested_attributes_for :children, :allow_destroy => false
+      matcher.allow_destroy(true).matches?(parent).should be_false
+      matcher.failure_message.should =~ /should allow destroy/
+    end
+  end
+
+  context "limit" do
+    it "should accept a correct value" do
+      Parent.accepts_nested_attributes_for :children, :limit => 3
+      matcher.limit(3).matches?(parent).should be_true
+    end
+
+    it "should reject a false value" do
+      Parent.accepts_nested_attributes_for :children, :limit => 3
+      matcher.limit(2).matches?(parent).should be_false
+      matcher.failure_message.should =~ /limit should be 2, got 3/
+    end
+  end
+
+  context "update_only" do
+    it "should accept a valid truthy value" do
+      Parent.accepts_nested_attributes_for :children, :update_only => true
+      matcher.update_only(true).matches?(parent).should be_true
+    end
+
+    it "should accept a valid falsey value" do
+      Parent.accepts_nested_attributes_for :children, :update_only => false
+      matcher.update_only(false).matches?(parent).should be_true
+    end
+
+    it "should reject an invalid truthy value" do
+      Parent.accepts_nested_attributes_for :children, :update_only => true
+      matcher.update_only(false).matches?(parent).should be_false
+      matcher.failure_message.should =~ /should not be update only/
+    end
+
+    it "should reject an invalid falsey value" do
+      Parent.accepts_nested_attributes_for :children, :update_only => false
+      matcher.update_only(true).matches?(parent).should be_false
+      matcher.failure_message.should =~ /should be update only/
+    end
+  end
+end