Add missing Command tests

test/test_command.rb

@@ -36,4 +36,21 @@ class TestCommand < Test::Unit::TestCase
       end
     end
   end
+  context "when calling .add_build_options" do
+    should "add common options" do
+      cmd = Object.new
+      mock(cmd).option.with_any_args.at_least(1)
+      Command.add_build_options(cmd)
+    end
+  end
+  context "when calling .process_site" do
+    context "when fatal error occurs" do
+      should "exit with non-zero error code" do
+        site = Object.new
+        stub(site).process { raise Jekyll::FatalException }
+        error = assert_raise(SystemExit) { Command.process_site(site) }
+        assert_not_equal 0, error.status
+      end
+    end
+  end
 end