Update resolving_with_sys_crates tests

Author: Nikita240

crates/resolver-tests/tests/resolve.rs

@@ -790,6 +790,34 @@ fn resolving_with_sys_crates() {
 
     let res = resolve(vec![dep_req("d", "1"), dep_req("r", "1")], &reg).unwrap();
 
+    assert_same(
+        &res,
+        &names(&[
+            ("root", "1.0.0"),
+            ("d", "1.0.0"),
+            ("r", "1.0.0"),
+            ("l-sys", "0.9.1"),
+            ("l", "0.9.1"),
+        ]),
+    );
+}
+
+#[test]
+fn resolving_with_sys_crates_duplicates() {
+    // This is based on issues/4902
+    // With `l` a normal library we get 2copies so everyone gets the newest compatible.
+    // But `l-sys` a library with a links attribute we make sure there is only one.
+    let reg = registry(vec![
+        pkg!(("l-sys", "0.9.1")),
+        pkg!(("l-sys", "0.10.0")),
+        pkg!(("l", "0.9.1") => [dep_req("l-sys", ">=0.8.0, <=0.10.0")]),
+        pkg!(("l", "0.10.0") => [dep_req("l-sys", "0.9")]),
+        pkg!(("d", "1.0.0") => [dep_req("l", "0.10")]),
+        pkg!(("r", "1.0.0") => [dep_req("l", "0.9")]),
+    ]);
+
+    let res = resolve(vec![dep_req("d", "1"), dep_req("r", "1")], &reg).unwrap();
+
     assert_same(
         &res,
         &names(&[