diff --git a/src/test/java/ru/ulstu/StreamApiUtilsTest.java b/src/test/java/ru/ulstu/StreamApiUtilsTest.java
index 5782cbb..417628e 100644
--- a/src/test/java/ru/ulstu/StreamApiUtilsTest.java
+++ b/src/test/java/ru/ulstu/StreamApiUtilsTest.java
@@ -16,4 +16,12 @@ public class StreamApiUtilsTest {
 
         assertEquals(integersInitial, integers);
     }
+
+    @Test
+    public void filedTestMappingByDay() {
+        List<Integer> integersInitial = List.of(1);
+        List<Integer> integers = StreamApiUtils.convert(List.of("1", "2"), Integer::valueOf);
+
+        assertEquals(integersInitial, integers);
+    }
 }