1 files changed, 20 insertions, 1 deletions
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.unique/unique_copy.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.unique/unique_copy.pass.cpp
index 761dad4ecd0..48ddcf921e4 100644
--- a/libcxx/test/std/algorithms/alg.modifying.operations/alg.unique/unique_copy.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.modifying.operations/alg.unique/unique_copy.pass.cpp
@@ -14,14 +14,29 @@
 //         && EqualityComparable<InIter::value_type>
 //         && HasAssign<InIter::value_type, InIter::reference>
 //         && Constructible<InIter::value_type, InIter::reference>
-//   OutIter
+//   constexpr OutIter        // constexpr after C++17
 //   unique_copy(InIter first, InIter last, OutIter result);
 
 #include <algorithm>
 #include <cassert>
 
+#include "test_macros.h"
 #include "test_iterators.h"
 
+#if TEST_STD_VER > 17
+TEST_CONSTEXPR bool test_constexpr() {
+          int ia[]       = {0, 1, 2, 2, 4};
+          int ib[]       = {0, 0, 0, 0, 0};
+    const int expected[] = {0, 1, 2, 4};
+
+    auto it = std::unique_copy(std::begin(ia), std::end(ia), std::begin(ib));
+    return it == (std::begin(ib) + std::size(expected))
+        && *it == 0 // don't overwrite final value in output
+        && std::equal(std::begin(ib), it, std::begin(expected), std::end(expected))
+        ;
+    }
+#endif
+
 template <class InIter, class OutIter>
 void
 test()
@@ -122,4 +137,8 @@ int main()
     test<const int*, bidirectional_iterator<int*> >();
     test<const int*, random_access_iterator<int*> >();
     test<const int*, int*>();
+
+#if TEST_STD_VER > 17
+    static_assert(test_constexpr());
+#endif
 }