1 files changed, 32 insertions, 0 deletions
diff --git a/compiler/rustc_data_structures/src/union_find/tests.rs b/compiler/rustc_data_structures/src/union_find/tests.rs
new file mode 100644
index 00000000000..34a4e4f8e6e
--- /dev/null
+++ b/compiler/rustc_data_structures/src/union_find/tests.rs
@@ -0,0 +1,32 @@
+use super::UnionFind;
+
+#[test]
+fn empty() {
+    let mut sets = UnionFind::<u32>::new(10);
+
+    for i in 1..10 {
+        assert_eq!(sets.find(i), i);
+    }
+}
+
+#[test]
+fn transitive() {
+    let mut sets = UnionFind::<u32>::new(10);
+
+    sets.unify(3, 7);
+    sets.unify(4, 2);
+
+    assert_eq!(sets.find(7), sets.find(3));
+    assert_eq!(sets.find(2), sets.find(4));
+    assert_ne!(sets.find(3), sets.find(4));
+
+    sets.unify(7, 4);
+
+    assert_eq!(sets.find(7), sets.find(3));
+    assert_eq!(sets.find(2), sets.find(4));
+    assert_eq!(sets.find(3), sets.find(4));
+
+    for i in [0, 1, 5, 6, 8, 9] {
+        assert_eq!(sets.find(i), i);
+    }
+}