eugenp · jzheaux · Oct 2, 2025 · Sep 21, 2025 · Sep 23, 2025 · Sep 23, 2025
diff --git a/spring-boot-modules/spring-boot-3-observation/pom.xml b/spring-boot-modules/spring-boot-3-observation/pom.xml
@@ -32,6 +32,11 @@
             <artifactId>micrometer-tracing-bridge-brave</artifactId>
             <!--artifactId>micrometer-tracing-bridge-otel</artifactId -->
         </dependency>
+        <dependency>
+            <groupId>io.micrometer</groupId>
+            <artifactId>micrometer-test</artifactId>
+            <scope>test</scope>
+        </dependency>
         <dependency>
             <groupId>io.micrometer</groupId>
             <artifactId>micrometer-observation-test</artifactId>

diff --git a/.../spring-boot-3-observation/src/main/java/com/baeldung/micrometer/test/FooApplication.java b/.../spring-boot-3-observation/src/main/java/com/baeldung/micrometer/test/FooApplication.java
@@ -0,0 +1,13 @@
+package com.baeldung.micrometer.test;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class FooApplication {
+
+    public static void main(String[] args) {
+        SpringApplication.run(FooApplication.class, args);
+    }
+
+}
diff --git a/...ules/spring-boot-3-observation/src/main/java/com/baeldung/micrometer/test/FooService.java b/...ules/spring-boot-3-observation/src/main/java/com/baeldung/micrometer/test/FooService.java
@@ -0,0 +1,38 @@
+package com.baeldung.micrometer.test;
+
+import java.util.concurrent.ThreadLocalRandom;
+
+import org.springframework.stereotype.Service;
+
+import io.micrometer.core.instrument.MeterRegistry;
+
+@Service
+public class FooService {
+
+    private final MeterRegistry registry;
+
+    public FooService(MeterRegistry registry) {
+        this.registry = registry;
+    }
+
+    public int foo() {
+        int delayedMs = registry.timer("foo.time")
+            .record(this::doSomething);
+
+        registry.counter("foo.count")
+            .increment();
+
+        return delayedMs;
+    }
+
+    private int doSomething() {
+        int delayMs = ThreadLocalRandom.current()
+            .nextInt(10, 100);
+        try {
+            Thread.sleep(delayMs);
+            return delayMs;
+        } catch (InterruptedException e) {
+            throw new RuntimeException(e);
+        }
+    }
+}
diff --git a/...t-3-observation/src/test/java/com/baeldung/micrometer/test/MicrometerIntegrationTest.java b/...t-3-observation/src/test/java/com/baeldung/micrometer/test/MicrometerIntegrationTest.java
@@ -0,0 +1,57 @@
+package com.baeldung.micrometer.test;
+
+import static java.time.Duration.ofMillis;
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.concurrent.TimeUnit;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+
+import io.micrometer.core.instrument.MeterRegistry;
+
+@SpringBootTest(classes = FooApplication.class )
+class MicrometerIntegrationTest {
+
+    @Autowired
+    private MeterRegistry meterRegistry;
+
+    @Autowired
+    private FooService fooService;
+
+    @BeforeEach
+    void reset() {
+        meterRegistry.clear();
+    }
+
+    @Test
+    void whenFooIsCalled_thenCounterIsIncremented() {
+        fooService.foo();
+        fooService.foo();
+        fooService.foo();
+
+        double invocations = meterRegistry.get("foo.count")
+            .counter()
+            .count();
+
+        assertThat(invocations)
+            .isEqualTo(3);
+    }
+
+    @Test
+    void whenFooIsCalled_thenTimerIsUpdated() {
+        fooService.foo();
+        fooService.foo();
+        fooService.foo();
+
+        int totalTimeMs = (int) meterRegistry.get("foo.time")
+            .timer()
+            .totalTime(TimeUnit.MILLISECONDS);
+
+        assertThat(ofMillis(totalTimeMs))
+            .isBetween(ofMillis(30), ofMillis(400));
+    }
+
+}
diff --git a/...ing-boot-3-observation/src/test/java/com/baeldung/micrometer/test/MicrometerUnitTest.java b/...ing-boot-3-observation/src/test/java/com/baeldung/micrometer/test/MicrometerUnitTest.java
@@ -0,0 +1,55 @@
+package com.baeldung.micrometer.test;
+
+import static java.time.Duration.ofMillis;
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.concurrent.TimeUnit;
+
+import org.junit.jupiter.api.Test;
+
+import io.micrometer.core.instrument.MeterRegistry;
+import io.micrometer.core.instrument.simple.SimpleMeterRegistry;
+import io.micrometer.core.tck.MeterRegistryAssert;
+
+class MicrometerUnitTest {
+
+    private MeterRegistry meterRegistry= new SimpleMeterRegistry();
+    private FooService fooService = new FooService(meterRegistry);
+
+    @Test
+    void whenFooIsCalled_thenCounterIsIncremented() {
+        fooService.foo();
+        fooService.foo();
+        fooService.foo();
+
+        double invocations = meterRegistry.get("foo.count")
+            .counter()
+            .count();
+
+        assertThat(invocations)
+            .isEqualTo(3);
+    }
+
+    @Test
+    void whenFooIsCalled_thenTimerIsUpdated() {
+        fooService.foo();
+        fooService.foo();
+        fooService.foo();
+
+        int totalTimeMs = (int) meterRegistry.get("foo.time")
+            .timer()
+            .totalTime(TimeUnit.MILLISECONDS);
+
+        assertThat(ofMillis(totalTimeMs))
+            .isBetween(ofMillis(30), ofMillis(400));
+    }
+
+    @Test
+    void whenFooIsCalled_thenTimerIsRegistered() {
+        fooService.foo();
+
+        MeterRegistryAssert.assertThat(meterRegistry)
+            .hasTimerWithName("foo.time");
+    }
+
+}