Add specs for simple in memory joins.

spec/relations/join_spec.rb

@@ -0,0 +1,40 @@
+require 'spec_helper'
+
+describe "Arel" do
+  before :all do
+    @owner = Arel::Model.build do |r|
+      r.engine Arel::Testing::Engine.new
+
+      r.attribute :id, Arel::Attributes::Integer
+    end
+
+    @thing = Arel::Model.build do |r|
+      r.engine Arel::Testing::Engine.new
+
+      r.attribute :id,       Arel::Attributes::Integer
+      r.attribute :owner_id, Arel::Attributes::Integer
+      r.attribute :age,      Arel::Attributes::Integer
+    end
+  end
+
+  describe "Join" do
+    before :all do
+      @relation = @thing.join(@owner).on(@thing[:owner_id].eq(@owner[:id]))
+      @expected = []
+
+      3.times do |owner_id|
+        @owner.insert([owner_id])
+
+        8.times do |i|
+          thing_id = owner_id * 8 + i
+          age      = 2 * thing_id
+
+          @thing.insert([thing_id, owner_id, age])
+          @expected << Arel::Row.new(@relation, [thing_id, owner_id, age, owner_id])
+        end
+      end
+    end
+
+    it_should_behave_like 'A Relation'
+  end
+end