diff --git a/unittests/ADT/SmallPtrSetTest.cpp b/unittests/ADT/SmallPtrSetTest.cpp
index 1b564ac05ac..d885f69b211 100644
--- a/unittests/ADT/SmallPtrSetTest.cpp
+++ b/unittests/ADT/SmallPtrSetTest.cpp
@@ -16,7 +16,30 @@
 
 using namespace llvm;
 
-// SmallPtrSet swapping test.
+TEST(SmallPtrSetTest, Assignment) {
+  int buf[8];
+  for (int i = 0; i < 8; ++i)
+    buf[i] = 0;
+
+  SmallPtrSet<int *, 4> s1;
+  s1.insert(&buf[0]);
+  s1.insert(&buf[1]);
+
+  SmallPtrSet<int *, 4> s2;
+  (s2 = s1).insert(&buf[2]);
+
+  // Self assign as well.
+  (s2 = s2).insert(&buf[3]);
+
+  s1 = s2;
+  EXPECT_EQ(4U, s1.size());
+  for (int i = 0; i < 8; ++i)
+    if (i < 4)
+      EXPECT_TRUE(s1.count(&buf[i]));
+    else
+      EXPECT_FALSE(s1.count(&buf[i]));
+}
+
 TEST(SmallPtrSetTest, GrowthTest) {
   int i;
   int buf[8];
@@ -112,6 +135,7 @@ TEST(SmallPtrSetTest, CopyAndMoveTest) {
     else
       EXPECT_FALSE(s3.count(&buf[i]));
 
+  // Move assign to the moved-from object.
   s1 = llvm_move(s3);
   EXPECT_EQ(4U, s1.size());
   for (int i = 0; i < 8; ++i)