Only remove a direct PowerMockTestCase or PowerMockConfiguration superclass in RemovePowerMockClassExtensions (#1224)

The recipe checked the `extends` clause with `TypeUtils.isAssignableTo`, so a test such as `class FooTest extends MyBaseTest`, where the user's own `MyBaseTest` extends `PowerMockTestCase`, also lost its superclass and with it every inherited helper, leaving code that no longer compiles. Matching the exact type with `TypeUtils.isOfClassType` unwraps only the base class that extends PowerMock directly and keeps subclasses of it intact.

Author: timtebeek

src/main/java/org/openrewrite/java/testing/mockito/RemovePowerMockClassExtensions.java

@@ -55,7 +55,7 @@ public J.ClassDeclaration visitClassDeclaration(J.ClassDeclaration classDecl, Ex
 
                     private J.ClassDeclaration maybeRemoveExtension(J.ClassDeclaration classDecl, String extensionFQN) {
                         TypeTree extension = classDecl.getExtends();
-                        if (extension != null && TypeUtils.isAssignableTo(extensionFQN, extension.getType())) {
+                        if (extension != null && TypeUtils.isOfClassType(extension.getType(), extensionFQN)) {
                             classDecl = classDecl.withExtends(null);
                             maybeRemoveImport(extensionFQN);
                         }

src/test/java/org/openrewrite/java/testing/mockito/RemovePowerMockClassExtensionsTest.java

@@ -81,4 +81,45 @@ public class MyPowerMockConfiguration {}
               """
           ));
     }
+
+    @Test
+    void subclassOfOwnBaseClassKeepsExtension() {
+        //language=java
+        rewriteRun(
+          java(
+            """
+              package org.powermock.modules.testng;
+
+              public class PowerMockTestCase {}
+              """
+          ),
+          java(
+            """
+              import org.powermock.modules.testng.PowerMockTestCase;
+
+              abstract class MyBaseTest extends PowerMockTestCase {
+                  protected int helper() {
+                      return 1;
+                  }
+              }
+              """,
+            """
+              abstract class MyBaseTest {
+                  protected int helper() {
+                      return 1;
+                  }
+              }
+              """
+          ),
+          java(
+            """
+              class FooTest extends MyBaseTest {
+                  void test() {
+                      helper();
+                  }
+              }
+              """
+          )
+        );
+    }
 }