Update rspec matcher to work with custom version association names

`have_a_version_with` and `have_a_version_with_changes` had the
`versions` association call hardcoded.
If `has_paper_trail` had the `versions` option set to something else
(e.g: `has_paper_trail versions: :paper_trail_versions`) the matcher
couldn't be used.

This fixes that issue by dynamically fetching the association name from
the `:versions_association_name` class attribute.

CHANGELOG.md

@@ -16,7 +16,8 @@ recommendations of [keepachangelog.com](http://keepachangelog.com/).
 
 ### Fixed
 
-- None
+- [#925](https://github.com/airblade/paper_trail/pull/925) - Update RSpec
+  matchers to work with custom version association names
 
 ## 6.0.2 (2016-12-13)
 

lib/paper_trail/frameworks/rspec.rb

@@ -25,10 +25,16 @@ end
 
 RSpec::Matchers.define :have_a_version_with do |attributes|
   # check if the model has a version with the specified attributes
-  match { |actual| actual.versions.where_object(attributes).any? }
+  match do |actual|
+    versions_association = actual.class.versions_association_name
+    actual.send(versions_association).where_object(attributes).any?
+  end
 end
 
 RSpec::Matchers.define :have_a_version_with_changes do |attributes|
   # check if the model has a version changes with the specified attributes
-  match { |actual| actual.versions.where_object_changes(attributes).any? }
+  match do |actual|
+    versions_association = actual.class.versions_association_name
+    actual.send(versions_association).where_object_changes(attributes).any?
+  end
 end

spec/models/document_spec.rb

@@ -0,0 +1,21 @@
+require "rails_helper"
+
+describe Document, type: :model do
+  describe "`have_a_version_with` matcher", versioning: true do
+    it "works with custom versions association" do
+      document = Document.create!(name: "Foo")
+      document.update_attributes!(name: "Bar")
+
+      expect(document).to have_a_version_with(name: "Foo")
+    end
+  end
+
+  describe "`have_a_version_with_changes` matcher", versioning: true do
+    it "works with custom versions association" do
+      document = Document.create!(name: "Foo")
+      document.update_attributes!(name: "Bar")
+
+      expect(document).to have_a_version_with_changes(name: "Bar")
+    end
+  end
+end