diff --git a/azure-pipelines.yml b/azure-pipelines.yml
index e3fb0018ea..98bd186382 100644
--- a/azure-pipelines.yml
+++ b/azure-pipelines.yml
@@ -46,23 +46,22 @@ jobs:
 
 - template: build-templates/gradle-common.yml@templates
   parameters:
-    vmImage: 'windows-latest'
     jdkVersion: '1.8'
-    jobName: 'WindowsJava8'
+    options: '-PtestVM=java21Home'
+    jobName: 'LinuxJava21'
     gradleTasks: 'check -x dependencyCheckAggregate'
 
 - template: build-templates/gradle-common.yml@templates
   parameters:
     vmImage: 'windows-latest'
     jdkVersion: '1.8'
-    options: '-PtestVM=java11Home'
-    jobName: 'WindowsJava11'
+    jobName: 'WindowsJava8'
     gradleTasks: 'check -x dependencyCheckAggregate'
 
 - template: build-templates/gradle-common.yml@templates
   parameters:
     vmImage: 'windows-latest'
     jdkVersion: '1.8'
-    options: '-PtestVM=java17Home'
-    jobName: 'WindowsJava17'
+    options: '-PtestVM=java21Home'
+    jobName: 'WindowsJava21'
     gradleTasks: 'check -x dependencyCheckAggregate'
diff --git a/build-logic/src/main/java/org/ehcache/build/conventions/JacocoConvention.java b/build-logic/src/main/java/org/ehcache/build/conventions/JacocoConvention.java
index 08e6487783..1be256d031 100644
--- a/build-logic/src/main/java/org/ehcache/build/conventions/JacocoConvention.java
+++ b/build-logic/src/main/java/org/ehcache/build/conventions/JacocoConvention.java
@@ -15,7 +15,7 @@ public void apply(Project project) {
     project.getPlugins().apply(JacocoPlugin.class);
 
     project.getExtensions().configure(JacocoPluginExtension.class, jacoco -> {
-      jacoco.setToolVersion("0.8.8");
+      jacoco.setToolVersion("0.8.11");
     });
 
     project.getTasks().withType(JacocoReport.class).configureEach(jacocoReport -> {
diff --git a/clustered/ehcache-client/src/test/java/org/ehcache/clustered/common/internal/store/operations/LazyValueHolderTest.java b/clustered/ehcache-client/src/test/java/org/ehcache/clustered/common/internal/store/operations/LazyValueHolderTest.java
index 2058d9c56a..b631d7dba6 100644
--- a/clustered/ehcache-client/src/test/java/org/ehcache/clustered/common/internal/store/operations/LazyValueHolderTest.java
+++ b/clustered/ehcache-client/src/test/java/org/ehcache/clustered/common/internal/store/operations/LazyValueHolderTest.java
@@ -42,7 +42,7 @@ public class LazyValueHolderTest {
   @Test
   public void testGetValueDecodeOnlyOnce() throws Exception {
     Date date = mock(Date.class);
-    ByteBuffer buffer = mock(ByteBuffer.class);
+    ByteBuffer buffer = ByteBuffer.allocate(0);
     doReturn(date).when(serializer).read(buffer);
 
     LazyValueHolder<Date> valueHolder = new LazyValueHolder<>(buffer, serializer);
@@ -56,7 +56,7 @@ public void testGetValueDecodeOnlyOnce() throws Exception {
   @Test
   public void testEncodeEncodesOnlyOnce() throws Exception {
     Date date = mock(Date.class);
-    ByteBuffer buffer = mock(ByteBuffer.class);
+    ByteBuffer buffer = ByteBuffer.allocate(0);
     doReturn(buffer).when(serializer).serialize(date);
 
     LazyValueHolder<Date> valueHolder = new LazyValueHolder<>(date);
diff --git a/ehcache-impl/src/test/java/org/ehcache/impl/internal/copy/SerializingCopierTest.java b/ehcache-impl/src/test/java/org/ehcache/impl/internal/copy/SerializingCopierTest.java
index f6616a55cc..92aa1212af 100644
--- a/ehcache-impl/src/test/java/org/ehcache/impl/internal/copy/SerializingCopierTest.java
+++ b/ehcache-impl/src/test/java/org/ehcache/impl/internal/copy/SerializingCopierTest.java
@@ -36,7 +36,7 @@ public class SerializingCopierTest {
   public void testCopy() throws Exception {
     Serializer<String> serializer = uncheckedGenericMock(Serializer.class);
     String in = new String("foo");
-    ByteBuffer buff = mock(ByteBuffer.class);
+    ByteBuffer buff = ByteBuffer.allocate(0);
     when(serializer.serialize(in)).thenReturn(buff);
     when(serializer.read(buff)).thenReturn(new String("foo"));
 
diff --git a/ehcache-xml/build.gradle b/ehcache-xml/build.gradle
index 4766e78001..6093eb2b0f 100644
--- a/ehcache-xml/build.gradle
+++ b/ehcache-xml/build.gradle
@@ -153,6 +153,11 @@ tasks.register('lowerBoundTest', Test) {
   classpath -= configurations.testRuntimeClasspath
   //add the classpath we want
   classpath += configurations.lowerBoundTestRuntimeClasspath
+
+  if (testJava.javaVersion.isJava9Compatible()) {
+    // Older JAXB versions do reflection on java.lang.ClassLoader
+    jvmArgs += '--add-opens=java.base/java.lang=ALL-UNNAMED'
+  }
 }
 
 tasks.register('jakartaTest', Test) {