Add test cases verifying that SafeERB works

If an upgrade to Rails breaks SafeERB, we'd like to find out.

spec/models/safe_erb_spec.rb

@@ -0,0 +1,20 @@
+require File.dirname(__FILE__) + '/../spec_helper'
+
+# Verify that our safe_erb patches are working.
+describe "An ERB template" do
+  before :each do
+    @template = ERB.new('<%= var %>')
+  end
+
+  it "should not raise an error when untained values are interpolated" do
+    var = "foo"
+    assert_equal var, @template.result(binding)
+  end
+
+  it "should raise an error when tained values are interpolated" do
+    assert_raise RuntimeError do
+      var = "foo".taint
+      @template.result(binding)
+    end
+  end
+end