diff --git a/mockito-tutorial/app/build.gradle.kts b/mockito-tutorial/app/build.gradle.kts
index 424b78f9..1bc83797 100644
--- a/mockito-tutorial/app/build.gradle.kts
+++ b/mockito-tutorial/app/build.gradle.kts
@@ -15,11 +15,17 @@ repositories {
     mavenCentral()
 }
 
+val mockitoAgent = configurations.create("mockitoAgent")
+
 dependencies {
     // Use JUnit Jupiter for testing.
     testImplementation(libs.junit.jupiter)
-
     testRuntimeOnly("org.junit.platform:junit-platform-launcher")
+
+    // Use Mockito for mocking.
+    // https://javadoc.io/doc/org.mockito/mockito-core/latest/org/mockito/Mockito.html#mockito-instrumentation
+    testImplementation(libs.mockito)
+    mockitoAgent(libs.mockito) { isTransitive = false }
 }
 
 // Apply a specific Java toolchain to ease working on different environments.
@@ -34,7 +40,13 @@ application {
     mainClass = "quality.software.Main"
 }
 
-tasks.named<Test>("test") {
-    // Use JUnit Platform for unit tests.
-    useJUnitPlatform()
-}
+tasks {
+    test {
+        // Use JUnit Platform for unit tests.
+        useJUnitPlatform()
+
+        // Mockito JDK21+ config
+        // https://javadoc.io/doc/org.mockito/mockito-core/latest/org/mockito/Mockito.html#mockito-instrumentation
+        jvmArgs("-javaagent:${mockitoAgent.asPath}")
+    }
+}
\ No newline at end of file
diff --git a/mockito-tutorial/gradle/libs.versions.toml b/mockito-tutorial/gradle/libs.versions.toml
index 239e149e..36adaf95 100644
--- a/mockito-tutorial/gradle/libs.versions.toml
+++ b/mockito-tutorial/gradle/libs.versions.toml
@@ -4,7 +4,9 @@
 [versions]
 guava = "33.2.1-jre"
 junit-jupiter = "5.10.3"
+mockito = "5.14.0"
 
 [libraries]
 guava = { module = "com.google.guava:guava", version.ref = "guava" }
 junit-jupiter = { module = "org.junit.jupiter:junit-jupiter", version.ref = "junit-jupiter" }
+mockito = { module = "org.mockito:mockito-core", version.ref = "mockito" }