diff --git a/src/test/java/org/folio/dcb/integration/kafka/KafkaServiceTest.java b/src/test/java/org/folio/dcb/integration/kafka/KafkaServiceTest.java
new file mode 100644
index 00000000..c8181861
--- /dev/null
+++ b/src/test/java/org/folio/dcb/integration/kafka/KafkaServiceTest.java
@@ -0,0 +1,65 @@
+package org.folio.dcb.integration.kafka;
+
+import static org.folio.dcb.integration.kafka.CirculationEventListener.CHECK_IN_LISTENER_ID;
+import static org.folio.dcb.integration.kafka.CirculationEventListener.CHECK_OUT_LOAN_LISTENER_ID;
+import static org.folio.dcb.integration.kafka.CirculationEventListener.REQUEST_LISTENER_ID;
+import static org.mockito.Mockito.inOrder;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+import org.springframework.kafka.config.KafkaListenerEndpointRegistry;
+import org.springframework.kafka.listener.MessageListenerContainer;
+
+@ExtendWith(MockitoExtension.class)
+class KafkaServiceTest {
+
+  @InjectMocks
+  private KafkaService kafkaService;
+
+  @Mock
+  private KafkaListenerEndpointRegistry kafkaListenerEndpointRegistry;
+
+  @Test
+  void restartEventListenersShouldRestartAllDefinedListeners() {
+    // TestMate-45dd7ecc27dbf76d9b9b89c85033baae
+    var loanContainer = mock(MessageListenerContainer.class);
+    var checkInContainer = mock(MessageListenerContainer.class);
+    var requestContainer = mock(MessageListenerContainer.class);
+    when(kafkaListenerEndpointRegistry.getListenerContainer(CHECK_OUT_LOAN_LISTENER_ID)).thenReturn(loanContainer);
+    when(kafkaListenerEndpointRegistry.getListenerContainer(CHECK_IN_LISTENER_ID)).thenReturn(checkInContainer);
+    when(kafkaListenerEndpointRegistry.getListenerContainer(REQUEST_LISTENER_ID)).thenReturn(requestContainer);
+    var inOrder = inOrder(loanContainer, checkInContainer, requestContainer);
+
+    kafkaService.restartEventListeners();
+
+    inOrder.verify(loanContainer).stop();
+    inOrder.verify(loanContainer).start();
+    inOrder.verify(checkInContainer).stop();
+    inOrder.verify(checkInContainer).start();
+    inOrder.verify(requestContainer).stop();
+    inOrder.verify(requestContainer).start();
+  }
+
+  @Test
+  void restartEventListenersShouldHandleMissingContainersGracefully() {
+    // TestMate-8b6eec42e68f12f44653dac2c23cba01
+    var loanContainer = mock(MessageListenerContainer.class);
+    var requestContainer = mock(MessageListenerContainer.class);
+    when(kafkaListenerEndpointRegistry.getListenerContainer(CHECK_OUT_LOAN_LISTENER_ID)).thenReturn(loanContainer);
+    when(kafkaListenerEndpointRegistry.getListenerContainer(CHECK_IN_LISTENER_ID)).thenReturn(null);
+    when(kafkaListenerEndpointRegistry.getListenerContainer(REQUEST_LISTENER_ID)).thenReturn(requestContainer);
+    var inOrder = inOrder(loanContainer, requestContainer);
+
+    kafkaService.restartEventListeners();
+
+    inOrder.verify(loanContainer).stop();
+    inOrder.verify(loanContainer).start();
+    inOrder.verify(requestContainer).stop();
+    inOrder.verify(requestContainer).start();
+  }
+}
diff --git a/src/test/java/org/folio/dcb/integration/kafka/TransactionHelperTest.java b/src/test/java/org/folio/dcb/integration/kafka/TransactionHelperTest.java
new file mode 100644
index 00000000..09ecd4af
--- /dev/null
+++ b/src/test/java/org/folio/dcb/integration/kafka/TransactionHelperTest.java
@@ -0,0 +1,75 @@
+package org.folio.dcb.integration.kafka;
+
+import static java.util.Collections.emptyMap;
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.nio.charset.StandardCharsets;
+import java.util.Map;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.junit.jupiter.MockitoExtension;
+import org.springframework.messaging.MessageHeaders;
+
+@ExtendWith(MockitoExtension.class)
+class TransactionHelperTest {
+
+  @Test
+  void getHeaderValue_positive_shouldReturnHeaderValueWhenExists() {
+    // TestMate-2d5040ffc335eec4a8a7920946d099b8
+    var headerName = "x-okapi-tenant";
+    var headerValue = "diku";
+    var defaultValue = "default-tenant";
+    var headers = new MessageHeaders(Map.of(headerName, headerValue.getBytes(StandardCharsets.UTF_8)));
+
+    var result = TransactionHelper.getHeaderValue(headers, headerName, defaultValue);
+
+    assertThat(result).hasSize(1).containsExactly(headerValue);
+  }
+
+  @Test
+  void getHeaderValue_positive_shouldReturnDefaultValueWhenHeaderMissing() {
+    // TestMate-0d2c51271449a74c5b6391cb2241f2a8
+    var headerName = "missing-header";
+    var defaultValue = "fallback";
+    var headers = new MessageHeaders(emptyMap());
+
+    var result = TransactionHelper.getHeaderValue(headers, headerName, defaultValue);
+
+    assertThat(result).hasSize(1).containsExactly(defaultValue);
+  }
+
+  @Test
+  void getHeaderValue_positive_shouldReturnEmptyListWhenBothValueAndDefaultAreNull() {
+    // TestMate-4423ae29a46220bb8c5e8ca0ce09bb97
+    var headerName = "non-existent-header";
+    var headers = new MessageHeaders(emptyMap());
+    var result = TransactionHelper.getHeaderValue(headers, headerName, null);
+    assertThat(result).isEmpty();
+  }
+
+  @Test
+  void getHeaderValue_positive_shouldHandleEmptyByteArrayHeader() {
+    // TestMate-bfbbbd329f6a2dc1d12c169998db4db5
+    var headerName = "test-header";
+    var defaultValue = "default";
+    var emptyHeaderValue = new byte[0];
+    var headers = new MessageHeaders(Map.of(headerName, emptyHeaderValue));
+
+    var result = TransactionHelper.getHeaderValue(headers, headerName, defaultValue);
+
+    assertThat(result).hasSize(1).containsExactly("");
+  }
+
+  @Test
+  void getHeaderValue_positive_shouldHandleSpecialCharactersInUtf8() {
+    // TestMate-75141cc3fdff80ada4b6ce4d76e31673
+    var headerName = "special-header";
+    var headerValue = "tést-vålue";
+    var defaultValue = "default";
+    var headers = new MessageHeaders(Map.of(headerName, headerValue.getBytes(StandardCharsets.UTF_8)));
+
+    var result = TransactionHelper.getHeaderValue(headers, headerName, defaultValue);
+
+    assertThat(result).hasSize(1).containsExactly(headerValue);
+  }
+}