Makes setting negative values to maxLength throw an IndexSize exception

tests/unit/style/attr.rs

@@ -0,0 +1,33 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use style::attr::AttrValue;
+use util::str::DOMString;
+
+#[test]
+fn test_from_limited_i32_should_be_default_when_less_than_0() {
+    let value = DOMString::from("-1");
+    match AttrValue::from_limited_i32(value, 0) {
+        AttrValue::Int(_, 0) => (),
+        _ => panic!("expected an IndexSize error")
+    }
+}
+
+#[test]
+fn test_from_limited_i32_should_parse_a_uint_when_value_is_0_or_greater() {
+    match AttrValue::from_limited_i32(DOMString::from("1"), 0) {
+        AttrValue::Int(_, 1) => (),
+        _ => panic!("expected an successful parsing")
+    }
+}
+
+#[test]
+fn test_from_limited_i32_should_keep_parsed_value_when_not_an_int() {
+    match AttrValue::from_limited_i32(DOMString::from("parsed-value"), 0) {
+        AttrValue::Int(p, 0) => {
+            assert_eq!(p, DOMString::from("parsed_value"))
+        },
+        _ => panic!("expected an successful parsing")
+    }
+}