Add test to ensure that the /assets theme reader doesn't clobber preexisting site files.

test/fixtures/test-theme/assets/application.coffee

@@ -0,0 +1,3 @@
+---
+---
+alert "From your theme."

test/source/assets/application.coffee

@@ -0,0 +1,3 @@
+---
+---
+alert "From your site."

test/test_filters.rb

@@ -475,7 +475,7 @@ class TestFilters < JekyllUnitTest
               g["items"].is_a?(Array),
               "The list of grouped items for '' is not an Array."
             )
-            assert_equal 14, g["items"].size
+            assert_equal 15, g["items"].size
           end
         end
       end

test/test_site.rb

@@ -180,6 +180,7 @@ class TestSite < JekyllUnitTest
         %#\ +.md
         .htaccess
         about.html
+        application.coffee
         bar.html
         coffeescript.coffee
         contacts.html

test/test_theme_assets_reader.rb

@@ -25,6 +25,7 @@ class TestThemeAssetsReader < JekyllUnitTest
 
   context "with a valid theme" do
     should "read all assets" do
+      @site.reset
       ThemeAssetsReader.new(@site).read
       assert_file_with_relative_path @site.static_files, "assets/img/logo.png"
       assert_file_with_relative_path @site.pages, "assets/style.scss"
@@ -38,15 +39,24 @@ class TestThemeAssetsReader < JekyllUnitTest
       assert_equal @site.in_dest_dir("assets/style.css"), file.destination(@site.dest)
       assert_includes file.output, ".sample {\n  color: black; }"
     end
+
+    should "not overwrite site content with the same relative path" do
+      @site.reset
+      @site.read
+
+      file = @site.pages.find { |f| f.relative_path == "assets/application.coffee" }
+      refute_nil file
+      assert_includes file.content, "alert \"From your site.\""
+    end
   end
 
   context "with a valid theme without an assets dir" do
     should "not read any assets" do
-      allow(Theme).to receive(:realpath_for).with(:sass).and_return(nil)
       site = fixture_site("theme" => "test-theme")
+      allow(site.theme).to receive(:assets_path).and_return(nil)
       ThemeAssetsReader.new(site).read
-      refute_file_with_relative_path @site.static_files, "assets/img/logo.png"
-      refute_file_with_relative_path @site.pages, "assets/style.scss"
+      refute_file_with_relative_path site.static_files, "assets/img/logo.png"
+      refute_file_with_relative_path site.pages, "assets/style.scss"
     end
   end
 
@@ -54,8 +64,8 @@ class TestThemeAssetsReader < JekyllUnitTest
     should "not read any assets" do
       site = fixture_site("theme" => nil)
       ThemeAssetsReader.new(site).read
-      refute_file_with_relative_path @site.static_files, "assets/img/logo.png"
-      refute_file_with_relative_path @site.pages, "assets/style.scss"
+      refute_file_with_relative_path site.static_files, "assets/img/logo.png"
+      refute_file_with_relative_path site.pages, "assets/style.scss"
     end
   end
 end