Initial contribution
diff --git a/src/html/entity_test.go b/src/html/entity_test.go
new file mode 100644
index 0000000..b53f866
--- /dev/null
+++ b/src/html/entity_test.go
@@ -0,0 +1,29 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package html
+
+import (
+	"testing"
+	"unicode/utf8"
+)
+
+func TestEntityLength(t *testing.T) {
+	// We verify that the length of UTF-8 encoding of each value is <= 1 + len(key).
+	// The +1 comes from the leading "&". This property implies that the length of
+	// unescaped text is <= the length of escaped text.
+	for k, v := range entity {
+		if 1+len(k) < utf8.RuneLen(v) {
+			t.Error("escaped entity &" + k + " is shorter than its UTF-8 encoding " + string(v))
+		}
+		if len(k) > longestEntityWithoutSemicolon && k[len(k)-1] != ';' {
+			t.Errorf("entity name %s is %d characters, but longestEntityWithoutSemicolon=%d", k, len(k), longestEntityWithoutSemicolon)
+		}
+	}
+	for k, v := range entity2 {
+		if 1+len(k) < utf8.RuneLen(v[0])+utf8.RuneLen(v[1]) {
+			t.Error("escaped entity &" + k + " is shorter than its UTF-8 encoding " + string(v[0]) + string(v[1]))
+		}
+	}
+}