1 files changed, 50 insertions, 0 deletions
diff --git a/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.unique/thread.lock.unique.cons/mutex.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.unique/thread.lock.unique.cons/mutex.pass.cpp
new file mode 100644
index 00000000000..1f7217a8300
--- /dev/null
+++ b/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.unique/thread.lock.unique.cons/mutex.pass.cpp
@@ -0,0 +1,50 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// UNSUPPORTED: libcpp-has-no-threads
+
+// <mutex>
+
+// template <class Mutex> class unique_lock;
+
+// explicit unique_lock(mutex_type& m);
+
+#include <mutex>
+#include <thread>
+#include <cstdlib>
+#include <cassert>
+
+std::mutex m;
+
+typedef std::chrono::system_clock Clock;
+typedef Clock::time_point time_point;
+typedef Clock::duration duration;
+typedef std::chrono::milliseconds ms;
+typedef std::chrono::nanoseconds ns;
+
+void f()
+{
+    time_point t0 = Clock::now();
+    time_point t1;
+    {
+    std::unique_lock<std::mutex> ul(m);
+    t1 = Clock::now();
+    }
+    ns d = t1 - t0 - ms(250);
+    assert(d < ms(50));  // within 50ms
+}
+
+int main()
+{
+    m.lock();
+    std::thread t(f);
+    std::this_thread::sleep_for(ms(250));
+    m.unlock();
+    t.join();
+}