diff --git a/pom.xml b/pom.xml
index 43ea01f..f6a68b9 100644
--- a/pom.xml
+++ b/pom.xml
@@ -99,6 +99,7 @@
 		<!-- dependencies -->
 
 		<version.org.keycloak>21.0.1</version.org.keycloak>
+		<version.org.mockito>5.1.1</version.org.mockito>
 		<version.org.testcontainers>1.17.6</version.org.testcontainers>
 
 	</properties>
@@ -116,6 +117,11 @@
 			</dependency>
 
 			<!-- test -->
+			<dependency>
+				<groupId>org.mockito</groupId>
+				<artifactId>mockito-junit-jupiter</artifactId>
+				<version>${version.org.mockito}</version>
+			</dependency>
 			<dependency>
 				<groupId>org.testcontainers</groupId>
 				<artifactId>testcontainers-bom</artifactId>
@@ -162,6 +168,11 @@
 		</dependency>
 
 		<!-- test -->
+		<dependency>
+			<groupId>org.mockito</groupId>
+			<artifactId>mockito-junit-jupiter</artifactId>
+			<scope>test</scope>
+		</dependency>
 		<dependency>
 			<groupId>org.testcontainers</groupId>
 			<artifactId>junit-jupiter</artifactId>
diff --git a/src/test/java/io/kokuwa/keycloak/metrics/KeycloakIT.java b/src/test/java/io/kokuwa/keycloak/metrics/KeycloakIT.java
index c3115fe..67d545c 100644
--- a/src/test/java/io/kokuwa/keycloak/metrics/KeycloakIT.java
+++ b/src/test/java/io/kokuwa/keycloak/metrics/KeycloakIT.java
@@ -16,6 +16,11 @@ import io.kokuwa.keycloak.metrics.junit.KeycloakClient;
 import io.kokuwa.keycloak.metrics.junit.KeycloakExtension;
 import io.kokuwa.keycloak.metrics.prometheus.Prometheus;
 
+/**
+ * Integration tests with Keycloak.
+ *
+ * @author Stephan Schnabel
+ */
 @ExtendWith(KeycloakExtension.class)
 public class KeycloakIT {
 
diff --git a/src/test/java/io/kokuwa/keycloak/metrics/MicrometerEventListenerTest.java b/src/test/java/io/kokuwa/keycloak/metrics/MicrometerEventListenerTest.java
new file mode 100644
index 0000000..29151d2
--- /dev/null
+++ b/src/test/java/io/kokuwa/keycloak/metrics/MicrometerEventListenerTest.java
@@ -0,0 +1,173 @@
+package io.kokuwa.keycloak.metrics;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.anyString;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import java.util.Map;
+import java.util.UUID;
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Nested;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.keycloak.events.Event;
+import org.keycloak.events.EventType;
+import org.keycloak.events.admin.AdminEvent;
+import org.keycloak.events.admin.OperationType;
+import org.keycloak.events.admin.ResourceType;
+import org.mockito.ArgumentCaptor;
+import org.mockito.Captor;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+
+import io.micrometer.core.instrument.Counter;
+import io.micrometer.core.instrument.MeterRegistry;
+
+/**
+ * Test for {@link MicrometerEventListener} with Mockito.
+ *
+ * @author Stephan Schnabel
+ */
+@ExtendWith(MockitoExtension.class)
+public class MicrometerEventListenerTest {
+
+	@InjectMocks
+	MicrometerEventListener listener;
+	@Mock
+	MeterRegistry registry;
+	@Mock
+	Counter counter;
+	@Captor
+	ArgumentCaptor<String> metricCaptor;
+	@Captor
+	ArgumentCaptor<String[]> tagsCaptor;
+
+	@BeforeEach
+	void setup() {
+		when(registry.counter(metricCaptor.capture(), tagsCaptor.capture())).thenReturn(counter);
+	}
+
+	@DisplayName("onEvent(Event)")
+	@Nested
+	class onEvent {
+
+		@DisplayName("without error")
+		@Test
+		void withoutError() {
+
+			var realmId = UUID.randomUUID().toString();
+			var clientId = UUID.randomUUID().toString();
+			var type = EventType.LOGIN;
+
+			listener.onEvent(toEvent(realmId, clientId, type, null));
+			assertEvent(realmId, clientId, type.toString(), "");
+		}
+
+		@DisplayName("with error")
+		@Test
+		void withError() {
+
+			var realmId = UUID.randomUUID().toString();
+			var clientId = UUID.randomUUID().toString();
+			var type = EventType.LOGIN_ERROR;
+			var error = UUID.randomUUID().toString();
+
+			listener.onEvent(toEvent(realmId, clientId, type, error));
+			assertEvent(realmId, clientId, type.toString(), error);
+		}
+
+		@DisplayName("all fields empty")
+		@Test
+		void fieldsEmpty() {
+			listener.onEvent(toEvent(null, null, null, null));
+			assertEvent("", "", "", "");
+		}
+
+		private Event toEvent(String realmId, String clientId, EventType type, String error) {
+			var event = new Event();
+			event.setRealmId(realmId);
+			event.setClientId(clientId);
+			event.setType(type);
+			event.setError(error);
+			return event;
+		}
+
+		private void assertEvent(String realm, String client, String type, String error) {
+			assertCounter("keycloak_event_user", Map.of(
+					"realm", realm,
+					"client", client,
+					"type", type,
+					"error", error));
+		}
+	}
+
+	@DisplayName("onEvent(AdminEvent,boolean)")
+	@Nested
+	class onAdminEvent {
+
+		@DisplayName("without error")
+		@Test
+		void withoutError() {
+
+			var realmId = UUID.randomUUID().toString();
+			var resource = ResourceType.USER;
+			var operation = OperationType.CREATE;
+
+			listener.onEvent(toAdminEvent(realmId, resource, operation, null), false);
+			assertAdminEvent(realmId, resource.toString(), operation.toString(), "");
+		}
+
+		@DisplayName("with error")
+		@Test
+		void withError() {
+
+			var realmId = UUID.randomUUID().toString();
+			var resource = ResourceType.USER;
+			var operation = OperationType.CREATE;
+			var error = UUID.randomUUID().toString();
+
+			listener.onEvent(toAdminEvent(realmId, resource, operation, error), false);
+			assertAdminEvent(realmId, resource.toString(), operation.toString(), error);
+		}
+
+		@DisplayName("all fields empty")
+		@Test
+		void fieldsEmpty() {
+			listener.onEvent(toAdminEvent(null, null, null, null), false);
+			assertAdminEvent("", "", "", "");
+		}
+
+		private AdminEvent toAdminEvent(String realmId, ResourceType resource, OperationType operation, String error) {
+			var event = new AdminEvent();
+			event.setRealmId(realmId);
+			event.setResourceType(resource);
+			event.setOperationType(operation);
+			event.setError(error);
+			return event;
+		}
+
+		private void assertAdminEvent(String realm, String resource, String operation, String error) {
+			assertCounter("keycloak_event_admin", Map.of(
+					"realm", realm,
+					"resource", resource,
+					"operation", operation,
+					"error", error));
+		}
+	}
+
+	private void assertCounter(String metric, Map<String, String> tags) {
+		verify(registry).counter(anyString(), any(String[].class));
+		verify(counter).increment();
+		assertEquals(metric, metricCaptor.getValue(), "metric");
+		assertEquals(tags, IntStream
+				.range(0, tagsCaptor.getValue().length / 2).mapToObj(i -> i * 2)
+				.collect(Collectors.toMap(i -> tagsCaptor.getValue()[i], i -> tagsCaptor.getValue()[i + 1])), "tags");
+	}
+}