diff --git a/build.gradle b/build.gradle
index 1e7e723..9657951 100644
--- a/build.gradle
+++ b/build.gradle
@@ -112,4 +112,5 @@ dependencies {
     implementation group: 'xalan', name: 'xalan', version: '2.7.2'
 
     testImplementation group: 'org.springframework.boot', name: 'spring-boot-starter-test'
+    testImplementation group: 'org.junit.jupiter', name: 'junit-jupiter-api', version: '5.10.2'
 }
diff --git a/src/test/java/ru/ulstu/StreamApiUtilsTest.java b/src/test/java/ru/ulstu/StreamApiUtilsTest.java
new file mode 100644
index 0000000..5782cbb
--- /dev/null
+++ b/src/test/java/ru/ulstu/StreamApiUtilsTest.java
@@ -0,0 +1,19 @@
+package ru.ulstu;
+
+
+import org.junit.jupiter.api.Test;
+import ru.ulstu.core.util.StreamApiUtils;
+
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class StreamApiUtilsTest {
+    @Test
+    public void testMappingByDay() {
+        List<Integer> integersInitial = List.of(1, 2);
+        List<Integer> integers = StreamApiUtils.convert(List.of("1", "2"), Integer::valueOf);
+
+        assertEquals(integersInitial, integers);
+    }
+}