test ownership in unescape_unicode_test

fluent-syntax/tests/unicode.rs

@@ -1,23 +1,33 @@
+use std::borrow::Cow;
+
 use fluent_syntax::unicode::{unescape_unicode, unescape_unicode_to_string};
 
-fn test_unescape_unicode(input: &str, output: &str) {
+/// Asserts that decoding unicode escape sequences in `input` matches `output`.
+/// When `borrowed` = true, asserts that the escaped value is passed back by reference.
+fn test_unescape_unicode(input: &str, output: &str, borrowed: bool) {
     let mut s = String::new();
     unescape_unicode(&mut s, input).expect("Failed to write.");
-    assert_eq!(&s, output);
+    assert_eq!(s, output);
     let result = unescape_unicode_to_string(input);
-    assert_eq!(&result, output);
+    assert_eq!(result, output);
+
+    assert_eq!(matches!(result, Cow::Borrowed(_)), borrowed);
 }
 
 #[test]
 fn unescape_unicode_test() {
-    test_unescape_unicode("foo", "foo");
-    test_unescape_unicode("foo \\\\", "foo \\");
-    test_unescape_unicode("foo \\\"", "foo \"");
-    test_unescape_unicode("foo \\\\ faa", "foo \\ faa");
-    test_unescape_unicode("foo \\\\ faa \\\\ fii", "foo \\ faa \\ fii");
-    test_unescape_unicode("foo \\\\\\\" faa \\\"\\\\ fii", "foo \\\" faa \"\\ fii");
-    test_unescape_unicode("\\u0041\\u004F", "AO");
-    test_unescape_unicode("\\uA", "�");
-    test_unescape_unicode("\\uA0Pl", "�");
-    test_unescape_unicode("\\d Foo", "� Foo");
+    test_unescape_unicode("foo", "foo", true);
+    test_unescape_unicode("foo \\\\", "foo \\", false);
+    test_unescape_unicode("foo \\\"", "foo \"", false);
+    test_unescape_unicode("foo \\\\ faa", "foo \\ faa", false);
+    test_unescape_unicode("foo \\\\ faa \\\\ fii", "foo \\ faa \\ fii", false);
+    test_unescape_unicode(
+        "foo \\\\\\\" faa \\\"\\\\ fii",
+        "foo \\\" faa \"\\ fii",
+        false,
+    );
+    test_unescape_unicode("\\u0041\\u004F", "AO", false);
+    test_unescape_unicode("\\uA", "�", false);
+    test_unescape_unicode("\\uA0Pl", "�", false);
+    test_unescape_unicode("\\d Foo", "� Foo", false);
 }