Fix module testing not working due to call to internal JUnit API (#2187)

Replaced the use of the internal JUnit class
`org.junit.platform.commons.util.ClassUtils` with a new custom
`org.spockframework.util.ClassUtil` class. 

fixes #1227

---------

Co-authored-by: Andreas Turban <[email protected]>
Co-authored-by: Leonard Brünings <[email protected]>

Author: 3 people

docs/release_notes.adoc

@@ -63,6 +63,8 @@ will now require that the spec is annotated with <<parallel_execution.adoc#isola
 * Fix handling of condition method calls and Groovy `with()` method spockPull:2162[]
 ** This could break tests using `with()` which relied on the bug in the past spockIssue:2269[]
 ** Use the Spock `with(yourObject)` instead of `yourObject.with()` or prefix it `!!` to fix your test
+* Fix module testing not working due to call to JUnit internal API spockPull:2187[]
+** This also fixes the usage of Spock with JUnit 6 in OSGi environments
 
 == 2.4-M7 (2025-11-23)
 

spock-core/src/main/java/org/spockframework/runtime/SpockNode.java

@@ -2,13 +2,13 @@
 
 import org.spockframework.runtime.model.*;
 import org.spockframework.runtime.model.parallel.ResourceAccessMode;
+import org.spockframework.util.ClassUtil;
 import org.spockframework.util.ExceptionUtil;
 import spock.config.RunnerConfiguration;
 
 import java.util.*;
 import java.util.stream.Collectors;
 
-import org.junit.platform.commons.util.ClassUtils;
 import org.junit.platform.engine.*;
 import org.junit.platform.engine.support.descriptor.*;
 import org.junit.platform.engine.support.hierarchical.*;
@@ -91,7 +91,7 @@ public Set<ExclusiveResource> getExclusiveResources() {
   protected static MethodSource featureToMethodSource(FeatureInfo info) {
     return MethodSource.from(info.getSpec().getBottomSpec().getReflection().getName(),
       info.getName(),
-      ClassUtils.nullSafeToString(info.getFeatureMethod().getReflection().getParameterTypes()) // TODO replace internal API
+      ClassUtil.nullSafeToString(info.getFeatureMethod().getReflection().getParameterTypes())
     );
   }
 

spock-core/src/main/java/org/spockframework/util/ClassUtil.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2025 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.spockframework.util;
+
+import java.util.Arrays;
+
+import static java.util.stream.Collectors.joining;
+
+/**
+ * Utility methods for working with {@link Class} objects.
+ *
+ * @since 2.4
+ */
+public class ClassUtil {
+  public static String nullSafeToString(@Nullable Class<?> clazz) {
+    return clazz == null ? "null" : clazz.getName();
+  }
+
+  public static String nullSafeToString(@Nullable Class<?>... clazzes) {
+    if (clazzes == null) return "";
+
+    return Arrays.stream(clazzes)
+      .map(ClassUtil::nullSafeToString)
+      .collect(joining(", "));
+  }
+}

spock-specs/src/test/groovy/org/spockframework/util/ClassUtilSpec.groovy

@@ -0,0 +1,47 @@
+/*
+ * Copyright 2025 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.spockframework.util
+
+import spock.lang.Specification
+
+class ClassUtilSpec extends Specification {
+  def "get string representation of class"() {
+    expect:
+    ClassUtil.nullSafeToString(clazz as Class<?>) == expectedString
+
+    where:
+    clazz     | expectedString
+    Set       | "java.util.Set"
+    Tuple     | "groovy.lang.Tuple"
+    ClassUtil | "org.spockframework.util.ClassUtil"
+    null      | "null"
+  }
+
+  def "get string representation of none, one, or multiple potentially null classes"(Class<?>[] clazzes, String expectedString) {
+    expect: "result is names from single class overload separated by a comma and space each"
+    ClassUtil.nullSafeToString(clazzes as Class<?>[]) == expectedString
+
+    where:
+    clazzes                 | expectedString
+    [List, Set, Queue, Map] | "java.util.List, java.util.Set, java.util.Queue, java.util.Map"
+    [File, null, URL]       | "java.io.File, null, java.net.URL"
+    [null, null]            | "null, null"
+    [File]                  | "java.io.File"
+    []                      | ""
+    null                    | ""
+  }
+}