test coverage of #prefix_for on join.

- it delegates to the relation containing the attribute
  - if the relation containing the attribute is an alias, it returns the alias

README

@@ -1,6 +1,6 @@
 == Abstract ==
 
-ActiveRelation is a Relational Algebra for Ruby. It simplifies the generation of both the simplest and the most complex of SQL queries and it transparently adapts to various RDBMS systems. It is intended to be a framework framework; that is, you can build your own ORM with it, focusing on innovative object and collection modeling as opposed to database compatibility and query generation.
+ActiveRelation is a Relational Algebra for Ruby. It 1) simplifies the generation of both the simplest and the most complex of SQL queries and it 2) transparently adapts to various RDBMS systems. It is intended to be a framework framework; that is, you can build your own ORM with it, focusing on innovative object and collection modeling as opposed to database compatibility and query generation.
 
 == A Gentle Introduction ==
 
@@ -58,7 +58,7 @@ The best property of the Relational is compositionality, or closure under all op
       .select(users[:name].equals('amy')) \
       .project(users[:id])                \
     # => SELECT users.id FROM users WHERE users.name = 'amy'
-s
+
 
 == Contributions ==
 

spec/active_relation/unit/predicates/binary_spec.rb

@@ -34,7 +34,7 @@ module ActiveRelation
     end
     
     describe '#descend' do
-      it "distributes over the predicates and attributes" do
+      it "distributes a block over the predicates and attributes" do
         ConcreteBinary.new(@attribute1, @attribute2).descend(&:qualify). \
           should == ConcreteBinary.new(@attribute1.qualify, @attribute2.qualify)
       end

spec/active_relation/unit/relations/join_spec.rb

@@ -25,6 +25,13 @@ module ActiveRelation
       end
     end
 
+    describe '#qualify' do
+      it 'descends' do
+        Join.new("INNER JOIN", @relation1, @relation2, @predicate).qualify. \
+          should == Join.new("INNER JOIN", @relation1, @relation2, @predicate).descend(&:qualify)
+      end
+    end
+    
     describe '#descend' do
       it 'distributes over the relations and predicates' do
         Join.new("INNER JOIN", @relation1, @relation2, @predicate).qualify. \
@@ -33,8 +40,27 @@ module ActiveRelation
     end
 
     describe '#prefix_for' do
-      it 'needs a test' do
-        pending
+      describe 'when the joined relations are simple' do
+        it "returns the name of the relation containing the attribute" do
+          Join.new("INNER JOIN", @relation1, @relation2, @predicate).prefix_for(@relation1[:id]) \
+            .should == @relation1.prefix_for(@relation1[:id])
+          Join.new("INNER JOIN", @relation1, @relation2, @predicate).prefix_for(@relation2[:id]) \
+            .should == @relation2.prefix_for(@relation2[:id])
+          
+        end
+      end
+      
+      describe 'when one of the joined relations is an alias' do
+        before do
+          @aliased_relation = @relation1.as(:alias)
+        end
+        
+        it "returns the alias of the relation containing the attribute" do
+          Join.new("INNER JOIN", @aliased_relation, @relation2, @predicate).prefix_for(@aliased_relation[:id]) \
+            .should == @aliased_relation.alias
+          Join.new("INNER JOIN", @aliased_relation, @relation2, @predicate).prefix_for(@relation2[:id]) \
+            .should == @relation2.prefix_for(@relation2[:id])
+        end
       end
     end
     

spec/active_relation/unit/relations/order_spec.rb

@@ -15,7 +15,7 @@ module ActiveRelation
     end
     
     describe '#descend' do
-      it "distributes over the relation and attributes" do
+      it "distributes a block over the relation and attributes" do
         Order.new(@relation, @attribute).descend(&:qualify). \
           should == Order.new(@relation.descend(&:qualify), @attribute.qualify)
       end

spec/active_relation/unit/relations/projection_spec.rb

@@ -31,14 +31,14 @@ module ActiveRelation
     end
   
     describe '#qualify' do
-      it "distributes over the relation and attributes" do
+      it "descends" do
         Projection.new(@relation, @attribute).qualify. \
           should == Projection.new(@relation, @attribute).descend(&:qualify)
       end
     end
     
     describe '#descend' do
-      it "distributes over the relation and attributes" do
+      it "distributes a block over the relation and attributes" do
         Projection.new(@relation, @attribute).descend(&:qualify). \
           should == Projection.new(@relation.descend(&:qualify), @attribute.qualify)
       end

spec/active_relation/unit/relations/range_spec.rb

@@ -14,7 +14,7 @@ module ActiveRelation
     end
     
     describe '#descend' do
-      it "distributes over the relation" do
+      it "distributes a block over the relation" do
         Range.new(@relation, @range).descend(&:qualify).should == Range.new(@relation.descend(&:qualify), @range)
       end
     end

spec/active_relation/unit/relations/rename_spec.rb

@@ -46,7 +46,7 @@ module ActiveRelation
     end
   
     describe '#descend' do
-      it "distributes over the relation and renames" do
+      it "distributes a block over the relation and renames" do
         Rename.new(@relation, @relation[:id] => :schmid).descend(&:qualify). \
           should == Rename.new(@relation.descend(&:qualify), @relation[:id].qualify => :schmid)
       end

spec/active_relation/unit/relations/selection_spec.rb

@@ -23,7 +23,7 @@ module ActiveRelation
     end
 
     describe '#descend' do
-      it "distributes over the relation and predicates" do
+      it "distributes a block over the relation and predicates" do
         Selection.new(@relation, @predicate).descend(&:qualify). \
           should == Selection.new(@relation.descend(&:qualify), @predicate.descend(&:qualify))
       end