LUCENE-9608: add a hand-triggered test error class.

lucene/test-framework/src/test/org/apache/lucene/util/TestPleaseFail.java

@@ -0,0 +1,36 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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
+ *
+ *     http://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.apache.lucene.util;
+
+import org.junit.Assert;
+
+/**
+ * This test is for manually causing assertion failures or errors (to
+ * trigger the event for occasional needs of testing the test framework
+ * itself from command line).
+ */
+public class TestPleaseFail extends LuceneTestCase {
+  public void testFail() {
+    Assert.assertNull("(intentional failure)", System.getProperty("please.fail"));
+  }
+
+  public void testError() {
+    if (System.getProperty("please.fail") != null) {
+      throw new RuntimeException("(intentional error)");
+    }
+  }
+}