Improve sequential paginator

fixes #2044, fixes #1298

test/unit/post_sets/favorite_test.rb

@@ -34,10 +34,15 @@ module PostSets
             assert_equal(1, @set.posts.size)
             assert_equal(@post_1.id, @set.posts.first.id)
           end
+
+          should "know what page it's on" do
+            refute(@set.favorites.is_first_page?)
+            refute(@set.favorites.is_last_page?)
+          end
         end
       end
 
-      context "a favorite set for after the second most recent post" do
+      context "a favorite set for after the third most recent post" do
         setup do
           id = ::Favorite.where(:user_id => @user.id, :post_id => @post_2.id).first.id
           ::Favorite.stubs(:records_per_page).returns(1)
@@ -45,10 +50,55 @@ module PostSets
         end
 
         context "a sequential paginator" do
-          should "return the most recent element" do
+          should "return the second most recent element" do
             assert_equal(1, @set.posts.size)
             assert_equal(@post_1.id, @set.posts.first.id)
           end
+
+          should "know what page it's on" do
+            refute(@set.favorites.is_first_page?)
+            refute(@set.favorites.is_last_page?)
+          end
+        end
+      end
+
+      context "a favorite set for before the second most recent post" do
+        setup do
+          id = ::Favorite.where(:user_id => @user.id, :post_id => @post_1.id).first.id
+          ::Favorite.stubs(:records_per_page).returns(1)
+          @set = PostSets::Favorite.new(@user.id, "b#{id}")
+        end
+
+        context "a sequential paginator" do
+          should "return the third most recent element" do
+            assert_equal(1, @set.posts.size)
+            assert_equal(@post_2.id, @set.posts.first.id)
+          end
+
+          should "know what page it's on" do
+            refute(@set.favorites.is_first_page?)
+            assert(@set.favorites.is_last_page?)
+          end
+        end
+      end
+
+      context "a favorite set for after the second most recent post" do
+        setup do
+          id = ::Favorite.where(:user_id => @user.id, :post_id => @post_1.id).first.id
+          ::Favorite.stubs(:records_per_page).returns(1)
+          @set = PostSets::Favorite.new(@user.id, "a#{id}")
+        end
+
+        context "a sequential paginator" do
+          should "return the most recent element" do
+            assert_equal(1, @set.posts.size)
+            assert_equal(@post_3.id, @set.posts.first.id)
+          end
+
+          should "know what page it's on" do
+            assert(@set.favorites.is_first_page?)
+            refute(@set.favorites.is_last_page?)
+          end
         end
       end
 
@@ -63,6 +113,11 @@ module PostSets
             assert_equal(1, @set.posts.size)
             assert_equal(@post_1.id, @set.posts.first.id)
           end
+
+          should "know what page it's on" do
+            refute(@set.favorites.is_first_page?)
+            refute(@set.favorites.is_last_page?)
+          end
         end
       end
 
@@ -76,6 +131,11 @@ module PostSets
           assert_equal(1, @set.posts.size)
           assert_equal(@post_3.id, @set.posts.first.id)
         end
+
+        should "know what page it's on" do
+          assert(@set.favorites.is_first_page?)
+          refute(@set.favorites.is_last_page?)
+        end
       end
     end
   end