Add basic RelatedContent model spec to check multiple models can be related

spec/models/relation_spec.rb

@@ -0,0 +1,26 @@
+require 'rails_helper'
+
+describe RelatedContent do
+
+  let(:parent_relationable) { create([:proposal, :debate, :budget_investment].sample) }
+  let(:child_relationable) { create([:proposal, :debate, :budget_investment].sample) }
+
+  it "should allow relationables from various classes" do
+    expect(build(:related_content, parent_relationable: parent_relationable, child_relationable: child_relationable)).to be_valid
+    expect(build(:related_content, parent_relationable: parent_relationable, child_relationable: child_relationable)).to be_valid
+    expect(build(:related_content, parent_relationable: parent_relationable, child_relationable: child_relationable)).to be_valid
+  end
+
+  it "should not allow empty relationables" do
+    expect(build(:related_content)).not_to be_valid
+    expect(build(:related_content, parent_relationable: parent_relationable)).not_to be_valid
+    expect(build(:related_content, child_relationable: child_relationable)).not_to be_valid
+  end
+
+  it "should not allow repeated related contents" do
+    related_content = create(:related_content, parent_relationable: parent_relationable, child_relationable: child_relationable)
+    new_related_content = build(:related_content, parent_relationable: related_content.parent_relationable, child_relationable: related_content.child_relationable)
+    expect(new_related_content).not_to be_valid
+  end
+
+end