1 files changed, 37 insertions, 0 deletions
diff --git a/library/cpp/iterator/ut/iterate_keys_ut.cpp b/library/cpp/iterator/ut/iterate_keys_ut.cpp
new file mode 100644
index 0000000000..49eb866b6e
--- /dev/null
+++ b/library/cpp/iterator/ut/iterate_keys_ut.cpp
@@ -0,0 +1,37 @@
+#include <library/cpp/iterator/iterate_keys.h>
+
+#include <library/cpp/testing/gtest/gtest.h>
+
+#include <map>
+
+using namespace testing;
+
+TEST(IterateKeys, ConstMappingIteration) {
+    const std::map<int, int> squares{
+        {1, 1},
+        {2, 4},
+        {3, 9},
+    };
+    EXPECT_THAT(
+        IterateKeys(squares),
+        ElementsAre(1, 2, 3)
+    );
+}
+
+TEST(IterateKeys, ConstMultiMappingIteration) {
+    const std::multimap<int, int> primesBelow{
+        {2, 2},
+        {5, 3},
+        {5, 5},
+        {11, 7},
+        {11, 11},
+        {23, 13},
+        {23, 17},
+        {23, 23},
+    };
+
+    EXPECT_THAT(
+        IterateKeys(primesBelow),
+        ElementsAre(2, 5, 5, 11, 11, 23, 23, 23)
+    );
+}