1 files changed, 19 insertions, 0 deletions
diff --git a/library/std/src/sys_common/net/tests.rs b/library/std/src/sys_common/net/tests.rs
new file mode 100644
index 00000000000..7d45621e09a
--- /dev/null
+++ b/library/std/src/sys_common/net/tests.rs
@@ -0,0 +1,19 @@
+use super::*;
+use crate::collections::HashMap;
+
+#[test]
+fn no_lookup_host_duplicates() {
+    let mut addrs = HashMap::new();
+    let lh = match LookupHost::try_from(("localhost", 0)) {
+        Ok(lh) => lh,
+        Err(e) => panic!("couldn't resolve `localhost': {}", e),
+    };
+    for sa in lh {
+        *addrs.entry(sa).or_insert(0) += 1;
+    }
+    assert_eq!(
+        addrs.iter().filter(|&(_, &v)| v > 1).collect::<Vec<_>>(),
+        vec![],
+        "There should be no duplicate localhost entries"
+    );
+}