Add tests for DnsNameRef traits.

tests/name_tests.rs

@@ -0,0 +1,28 @@
+use ring::test::{compile_time_assert_send, compile_time_assert_sync};
+use webpki::DnsNameRef;
+
+#[test]
+fn test_dns_name_ref_traits() {
+    compile_time_assert_send::<DnsNameRef>();
+    compile_time_assert_sync::<DnsNameRef>();
+
+    let a = DnsNameRef::try_from_ascii(b"example.com").unwrap();
+
+    // `Copy`
+    {
+        let _b = a;
+        let _c = a;
+    }
+
+    // `Clone`
+    #[allow(clippy::clone_on_copy)]
+    let _ = a.clone();
+    // TODO: verify the clone is the same as `a`.
+
+    // TODO: Don't require `alloc` for these.
+    #[cfg(feature = "alloc")]
+    {
+        // `Debug`.
+        assert_eq!(format!("{:?}", &a), "DnsNameRef(\"example.com\")");
+    }
+}