Add tests for Cow::from for strings, vectors and slices

src/libcollectionstest/str.rs

@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+use std::borrow::Cow;
 use std::cmp::Ordering::{Equal, Greater, Less};
 use std::str::from_utf8;
 
@@ -1267,6 +1268,16 @@ fn test_box_slice_clone() {
     assert_eq!(data, data2);
 }
 
+#[test]
+fn test_cow_from() {
+    let borrowed = "borrowed";
+    let owned = String::from("owned");
+    match (Cow::from(owned.clone()), Cow::from(borrowed)) {
+        (Cow::Owned(o), Cow::Borrowed(b)) => assert!(o == owned && b == borrowed),
+        _ => panic!("invalid `Cow::from`"),
+    }
+}
+
 mod pattern {
     use std::str::pattern::Pattern;
     use std::str::pattern::{Searcher, ReverseSearcher};

src/libcollectionstest/vec.rs

@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+use std::borrow::Cow;
 use std::iter::{FromIterator, repeat};
 use std::mem::size_of;
 
@@ -466,6 +467,16 @@ fn test_into_iter_count() {
     assert_eq!(vec![1, 2, 3].into_iter().count(), 3);
 }
 
+#[test]
+fn test_cow_from() {
+    let borrowed: &[_] = &["borrowed", "(slice)"];
+    let owned = vec!["owned", "(vec)"];
+    match (Cow::from(owned.clone()), Cow::from(borrowed)) {
+        (Cow::Owned(o), Cow::Borrowed(b)) => assert!(o == owned && b == borrowed),
+        _ => panic!("invalid `Cow::from`"),
+    }
+}
+
 #[bench]
 fn bench_new(b: &mut Bencher) {
     b.iter(|| {