Add test case capturing slow regex.

Related to #90.

test/html5/test_sanitizer.rb

@@ -31,6 +31,12 @@ def check_sanitization(input, htmloutput, xhtmloutput, rexmloutput)
       %Q{given:    "#{input}"\nexpected: "#{htmloutput}"\ngot:      "#{sane}"})
   end
 
+  def assert_completes_in_reasonable_time &block
+    t0 = Time.now
+    block.call
+    assert_in_delta t0, Time.now, 0.01 # arbitrary seconds
+  end
+
   (HTML5::WhiteList::ALLOWED_ELEMENTS).each do |tag_name|
     define_method "test_should_allow_#{tag_name}_tag" do
       input       = "<#{tag_name} title='1'>foo <bad>bar</bad> baz</#{tag_name}>"
@@ -233,6 +239,14 @@ def test_css_negative_value_sanitization_shorthand_css_properties
     sane = Nokogiri::HTML(Loofah.scrub_fragment(html, :escape).to_xml)
     assert_match %r/-0.05em/, sane.inner_html
   end
+
+  def test_issue_90_slow_regex
+    html = %q{<span style="background: url('data:image/svg&#43;xml;charset=utf-8,%3Csvg%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%22%20width%3D%2232%22%20height%3D%2232%22%20viewBox%3D%220%200%2032%2032%22%3E%3Cpath%20fill%3D%22%23D4C8AE%22%20d%3D%22M0%200h32v32h-32z%22%2F%3E%3Cpath%20fill%3D%22%2383604B%22%20d%3D%22M0%200h31.99v11.75h-31.99z%22%2F%3E%3Cpath%20fill%3D%22%233D2319%22%20d%3D%22M0%2011.5h32v.5h-32z%22%2F%3E%3Cpath%20fill%3D%22%23F83651%22%20d%3D%22M5%200h1v10.5h-1z%22%2F%3E%3Cpath%20fill%3D%22%23FCD050%22%20d%3D%22M6%200h1v10.5h-1z%22%2F%3E%3Cpath%20fill%3D%22%2371C797%22%20d%3D%22M7%200h1v10.5h-1z%22%2F%3E%3Cpath%20fill%3D%22%23509CF9%22%20d%3D%22M8%200h1v10.5h-1z%22%2F%3E%3ClinearGradient%20id%3D%22a%22%20gradientUnits%3D%22userSpaceOnUse%22%20x1%3D%2224.996%22%20y1%3D%2210.5%22%20x2%3D%2224.996%22%20y2%3D%224.5%22%3E%3Cstop%20offset%3D%220%22%20stop-color%3D%22%23796055%22%2F%3E%3Cstop%20offset%3D%22.434%22%20stop-color%3D%22%23614C43%22%2F%3E%3Cstop%20offset%3D%221%22%20stop-color%3D%22%233D2D28%22%2F%3E%3C%2FlinearGradient%3E%3Cpath%20fill%3D%22url(%23a)%22%20d%3D%22M28%208.5c0%201.1-.9%202-2%202h-2c-1.1%200-2-.9-2-2v-2c0-1.1.9-2%202-2h2c1.1%200%202%20.9%202%202v2z%22%2F%3E%3Cpath%20fill%3D%22%235F402E%22%20d%3D%22M28%208c0%201.1-.9%202-2%202h-2c-1.1%200-2-.9-2-2v-2c0-1.1.9-2%202-2h2c1.1%200%202%20.9%202%202v2z%22%2F%3E%3C');"></span>}
+
+    assert_completes_in_reasonable_time {
+      sane = Nokogiri::HTML(Loofah.scrub_fragment(html, :strip).to_html)
+    }
+  end
 end
 
 # <html5_license>