LUCENE-7252: add TestCoreParser.testTermQueryEmptyXML test

lucene/queryparser/src/test/org/apache/lucene/queryparser/xml/TermQueryEmpty.xml

@@ -0,0 +1,18 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+ 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.
+-->
+<TermQuery fieldName="contents"></TermQuery>

lucene/queryparser/src/test/org/apache/lucene/queryparser/xml/TestCoreParser.java

@@ -66,6 +66,11 @@ public class TestCoreParser extends LuceneTestCase {
     dumpResults("TermQuery", q, 5);
   }
 
+  public void testTermQueryEmptyXML() throws ParserException, IOException {
+    parseShouldFail("TermQueryEmpty.xml",
+        "TermQuery has no text");
+  }
+
   public void testTermsQueryXML() throws ParserException, IOException {
     Query q = parse("TermsQuery.xml");
     dumpResults("TermsQuery", q, 5);
@@ -207,6 +212,20 @@ public class TestCoreParser extends LuceneTestCase {
     return indexData().searcher;
   }
 
+  protected void parseShouldFail(String xmlFileName, String expectedParserExceptionMessage) throws IOException {
+    Query q = null;
+    ParserException pe = null;
+    try {
+      q = parse(xmlFileName);
+    } catch (ParserException e) {
+      pe = e;
+    }
+    assertNull("for "+xmlFileName+" unexpectedly got "+q, q);
+    assertNotNull("expected a ParserException for "+xmlFileName, pe);
+    assertEquals("expected different ParserException for "+xmlFileName,
+        expectedParserExceptionMessage, pe.getMessage());
+  }
+
   protected Query parse(String xmlFileName) throws ParserException, IOException {
     try (InputStream xmlStream = TestCoreParser.class.getResourceAsStream(xmlFileName)) {
       assertNotNull("Test XML file " + xmlFileName + " cannot be found", xmlStream);