SOLR-8674: solr.tests.mergePolicy[Factory] tests now randomly choose between <mergePolicy> and <mergePolicyFactory>

* This increases <mergePolicy> vs. <mergePolicyFactory> test coverage.
* This temporarily also adds a little test setup complexity but when SOLR-8668 removes support for <mergePolicy> then test setup will return to its original complexity.

solr/contrib/analytics/src/test-files/solr/collection1/conf/solrconfig.snippet.randomindexconfig.xml

@@ -26,7 +26,7 @@ A solrconfig.xml snippet containing indexConfig settings for randomized testing.
        the RandomMergePolicy in all tests - but some tests expect very specific
        Merge behavior, so those tests can set it as needed.
   -->
-  <mergePolicy class="${solr.tests.mergePolicy:org.apache.solr.util.RandomMergePolicy}" />
+  <mergePolicyFactory class="${solr.tests.mergePolicyFactory:org.apache.solr.util.RandomMergePolicyFactory}" />
   
   <useCompoundFile>${useCompoundFile:false}</useCompoundFile>
 

solr/core/src/test-files/solr/collection1/conf/solrconfig-delpolicy1.xml

@@ -30,7 +30,8 @@
          to configure an explicit deletion policy, but we still wnat to randomize as much 
          as possible. 
     -->
-    <mergePolicy class="${solr.tests.mergePolicy:org.apache.solr.util.RandomMergePolicy}" />
+    <mergePolicy enable="${solr.tests.useMergePolicy:true}" class="${solr.tests.mergePolicy:org.apache.solr.util.RandomMergePolicy}" />
+    <mergePolicyFactory enable="${solr.tests.useMergePolicyFactory:true}" class="${solr.tests.mergePolicyFactory:org.apache.solr.util.RandomMergePolicyFactory}" />
     <useCompoundFile>${useCompoundFile:false}</useCompoundFile>
 
     <maxBufferedDocs>${solr.tests.maxBufferedDocs}</maxBufferedDocs>

solr/core/src/test-files/solr/collection1/conf/solrconfig-delpolicy2.xml

@@ -27,7 +27,8 @@
          to configure an explicit deletion policy, but we still wnat to randomize as much 
          as possible. 
     -->
-    <mergePolicy class="${solr.tests.mergePolicy:org.apache.solr.util.RandomMergePolicy}" />
+    <mergePolicy enable="${solr.tests.useMergePolicy:true}" class="${solr.tests.mergePolicy:org.apache.solr.util.RandomMergePolicy}" />
+    <mergePolicyFactory enable="${solr.tests.useMergePolicyFactory:true}" class="${solr.tests.mergePolicyFactory:org.apache.solr.util.RandomMergePolicyFactory}" />
     <useCompoundFile>${useCompoundFile:false}</useCompoundFile>
 
     <maxBufferedDocs>${solr.tests.maxBufferedDocs}</maxBufferedDocs>

solr/core/src/test-files/solr/collection1/conf/solrconfig-spellcheckcomponent.xml

@@ -20,7 +20,8 @@
 <config>
   <luceneMatchVersion>${tests.luceneMatchVersion:LATEST}</luceneMatchVersion>
   <indexConfig>
-    <mergePolicy class="${solr.tests.mergePolicy:org.apache.solr.util.RandomMergePolicy}" />  
+    <mergePolicy enable="${solr.tests.useMergePolicy:true}" class="${solr.tests.mergePolicy:org.apache.solr.util.RandomMergePolicy}" />
+    <mergePolicyFactory enable="${solr.tests.useMergePolicyFactory:true}" class="${solr.tests.mergePolicyFactory:org.apache.solr.util.RandomMergePolicyFactory}" />
     <useCompoundFile>${useCompoundFile:false}</useCompoundFile>
     <maxBufferedDocs>${solr.tests.maxBufferedDocs}</maxBufferedDocs>
     <ramBufferSizeMB>${solr.tests.ramBufferSizeMB}</ramBufferSizeMB>

solr/core/src/test-files/solr/collection1/conf/solrconfig.snippet.randomindexconfig.xml

@@ -26,7 +26,8 @@ A solrconfig.xml snippet containing indexConfig settings for randomized testing.
        the RandomMergePolicy in all tests - but some tests expect very specific
        Merge behavior, so those tests can set it as needed.
   -->
-  <mergePolicyFactory class="org.apache.solr.util.RandomMergePolicyFactory" />
+  <mergePolicy enable="${solr.tests.useMergePolicy:true}" class="${solr.tests.mergePolicy:org.apache.solr.util.RandomMergePolicy}" />
+  <mergePolicyFactory enable="${solr.tests.useMergePolicyFactory:true}" class="${solr.tests.mergePolicyFactory:org.apache.solr.util.RandomMergePolicyFactory}" />
   
   <useCompoundFile>${useCompoundFile:false}</useCompoundFile>
 

solr/core/src/test/org/apache/solr/TestGroupingSearch.java

@@ -34,12 +34,14 @@ import org.apache.lucene.index.LogDocMergePolicy;
 import org.apache.solr.client.solrj.impl.BinaryResponseParser;
 import org.apache.solr.common.params.CommonParams;
 import org.apache.solr.common.params.GroupParams;
+import org.apache.solr.index.LogDocMergePolicyFactory;
 import org.apache.solr.request.SolrQueryRequest;
 import org.apache.solr.request.SolrRequestInfo;
 import org.apache.solr.response.BinaryResponseWriter;
 import org.apache.solr.response.ResultContext;
 import org.apache.solr.response.SolrQueryResponse;
 import org.apache.solr.schema.IndexSchema;
+import org.junit.AfterClass;
 import org.junit.Before;
 import org.junit.BeforeClass;
 import org.junit.Test;
@@ -61,13 +63,19 @@ public class TestGroupingSearch extends SolrTestCaseJ4 {
   public static void beforeTests() throws Exception {
     // force LogDocMergePolicy so that we get a predictable doc order
     // when doing unsorted group collection
-    System.setProperty("solr.tests.mergePolicy", 
-                       LogDocMergePolicy.class.getName());
+    systemSetPropertySolrTestsMergePolicy(LogDocMergePolicy.class.getName());
+    systemSetPropertySolrTestsMergePolicyFactory(LogDocMergePolicyFactory.class.getName());
 
     System.setProperty("enable.update.log", "false"); // schema12 doesn't support _version_
     initCore("solrconfig.xml", "schema12.xml");
   }
 
+  @AfterClass
+  public static void afterTests() {
+    systemClearPropertySolrTestsMergePolicy();
+    systemClearPropertySolrTestsMergePolicyFactory();
+  }
+
   @Before
   public void cleanIndex() {
     assertU(delQ("*:*"));

solr/core/src/test/org/apache/solr/cloud/TestMiniSolrCloudCluster.java

@@ -31,6 +31,7 @@ import java.util.concurrent.atomic.AtomicInteger;
 
 import com.carrotsearch.randomizedtesting.rules.SystemPropertiesRestoreRule;
 
+import org.apache.lucene.index.TieredMergePolicy;
 import org.apache.lucene.util.LuceneTestCase;
 import org.apache.lucene.util.LuceneTestCase.SuppressSysoutChecks;
 import org.apache.solr.SolrTestCaseJ4;
@@ -48,6 +49,7 @@ import org.apache.solr.common.cloud.Slice;
 import org.apache.solr.common.cloud.SolrZkClient;
 import org.apache.solr.common.cloud.ZkStateReader;
 import org.apache.solr.core.CoreDescriptor;
+import org.apache.solr.index.TieredMergePolicyFactory;
 import org.apache.solr.util.RevertDefaultThreadHandlerRule;
 import org.junit.ClassRule;
 import org.junit.Rule;
@@ -105,7 +107,15 @@ public class TestMiniSolrCloudCluster extends LuceneTestCase {
     collectionProperties.putIfAbsent("solr.tests.maxBufferedDocs", "100000");
     collectionProperties.putIfAbsent("solr.tests.ramBufferSizeMB", "100");
     // use non-test classes so RandomizedRunner isn't necessary
-    collectionProperties.putIfAbsent("solr.tests.mergePolicy", "org.apache.lucene.index.TieredMergePolicy");
+    if (random().nextBoolean()) {
+      collectionProperties.putIfAbsent(SolrTestCaseJ4.SYSTEM_PROPERTY_SOLR_TESTS_MERGEPOLICY, TieredMergePolicy.class.getName());
+      collectionProperties.putIfAbsent(SolrTestCaseJ4.SYSTEM_PROPERTY_SOLR_TESTS_USEMERGEPOLICY, "true");
+      collectionProperties.putIfAbsent(SolrTestCaseJ4.SYSTEM_PROPERTY_SOLR_TESTS_USEMERGEPOLICYFACTORY, "false");
+    } else {
+      collectionProperties.putIfAbsent(SolrTestCaseJ4.SYSTEM_PROPERTY_SOLR_TESTS_MERGEPOLICYFACTORY, TieredMergePolicyFactory.class.getName());
+      collectionProperties.putIfAbsent(SolrTestCaseJ4.SYSTEM_PROPERTY_SOLR_TESTS_USEMERGEPOLICYFACTORY, "true");
+      collectionProperties.putIfAbsent(SolrTestCaseJ4.SYSTEM_PROPERTY_SOLR_TESTS_USEMERGEPOLICY, "false");
+    }
     collectionProperties.putIfAbsent("solr.tests.mergeScheduler", "org.apache.lucene.index.ConcurrentMergeScheduler");
     collectionProperties.putIfAbsent("solr.directoryFactory", (persistIndex ? "solr.StandardDirectoryFactory" : "solr.RAMDirectoryFactory"));
     

solr/core/src/test/org/apache/solr/cloud/TestMiniSolrCloudClusterBase.java

@@ -24,6 +24,7 @@ import java.util.List;
 import java.util.Map;
 
 import com.carrotsearch.randomizedtesting.rules.SystemPropertiesRestoreRule;
+import org.apache.lucene.index.TieredMergePolicy;
 import org.apache.lucene.util.LuceneTestCase;
 import org.apache.solr.SolrTestCaseJ4;
 import org.apache.solr.client.solrj.SolrQuery;
@@ -39,6 +40,7 @@ import org.apache.solr.common.cloud.Slice;
 import org.apache.solr.common.cloud.SolrZkClient;
 import org.apache.solr.common.cloud.ZkStateReader;
 import org.apache.solr.core.CoreDescriptor;
+import org.apache.solr.index.TieredMergePolicyFactory;
 import org.apache.solr.util.RevertDefaultThreadHandlerRule;
 import org.junit.ClassRule;
 import org.junit.Rule;
@@ -93,7 +95,15 @@ public class TestMiniSolrCloudClusterBase extends LuceneTestCase {
     collectionProperties.put("solr.tests.maxBufferedDocs", "100000");
     collectionProperties.put("solr.tests.ramBufferSizeMB", "100");
     // use non-test classes so RandomizedRunner isn't necessary
-    collectionProperties.put("solr.tests.mergePolicy", "org.apache.lucene.index.TieredMergePolicy");
+    if (random().nextBoolean()) {
+      collectionProperties.put(SolrTestCaseJ4.SYSTEM_PROPERTY_SOLR_TESTS_MERGEPOLICY, TieredMergePolicy.class.getName());
+      collectionProperties.put(SolrTestCaseJ4.SYSTEM_PROPERTY_SOLR_TESTS_USEMERGEPOLICY, "true");
+      collectionProperties.put(SolrTestCaseJ4.SYSTEM_PROPERTY_SOLR_TESTS_USEMERGEPOLICYFACTORY, "false");
+    } else {
+      collectionProperties.put(SolrTestCaseJ4.SYSTEM_PROPERTY_SOLR_TESTS_MERGEPOLICYFACTORY, TieredMergePolicyFactory.class.getName());
+      collectionProperties.put(SolrTestCaseJ4.SYSTEM_PROPERTY_SOLR_TESTS_USEMERGEPOLICYFACTORY, "true");
+      collectionProperties.put(SolrTestCaseJ4.SYSTEM_PROPERTY_SOLR_TESTS_USEMERGEPOLICY, "false");
+    }
     collectionProperties.put("solr.tests.mergeScheduler", "org.apache.lucene.index.ConcurrentMergeScheduler");
     collectionProperties.put("solr.directoryFactory", "solr.RAMDirectoryFactory");
 

solr/core/src/test/org/apache/solr/cloud/TestSolrCloudWithKerberosAlt.java

@@ -28,6 +28,7 @@ import com.carrotsearch.randomizedtesting.rules.SystemPropertiesRestoreRule;
 
 import org.apache.commons.io.FileUtils;
 import org.apache.hadoop.minikdc.MiniKdc;
+import org.apache.lucene.index.TieredMergePolicy;
 import org.apache.lucene.util.Constants;
 import org.apache.lucene.util.LuceneTestCase;
 import org.apache.solr.SolrTestCaseJ4;
@@ -43,6 +44,7 @@ import org.apache.solr.common.SolrInputDocument;
 import org.apache.solr.common.cloud.SolrZkClient;
 import org.apache.solr.common.cloud.ZkStateReader;
 import org.apache.solr.core.CoreDescriptor;
+import org.apache.solr.index.TieredMergePolicyFactory;
 import org.apache.solr.util.BadZookeeperThreadsFilter;
 import org.apache.solr.util.RevertDefaultThreadHandlerRule;
 import org.junit.BeforeClass;
@@ -185,7 +187,15 @@ public class TestSolrCloudWithKerberosAlt extends LuceneTestCase {
       properties.put("solr.tests.maxBufferedDocs", "100000");
       properties.put("solr.tests.ramBufferSizeMB", "100");
       // use non-test classes so RandomizedRunner isn't necessary
-      properties.put("solr.tests.mergePolicy", "org.apache.lucene.index.TieredMergePolicy");
+      if (random().nextBoolean()) {
+        properties.put(SolrTestCaseJ4.SYSTEM_PROPERTY_SOLR_TESTS_MERGEPOLICY, TieredMergePolicy.class.getName());
+        properties.put(SolrTestCaseJ4.SYSTEM_PROPERTY_SOLR_TESTS_USEMERGEPOLICY, "true");
+        properties.put(SolrTestCaseJ4.SYSTEM_PROPERTY_SOLR_TESTS_USEMERGEPOLICYFACTORY, "false");
+      } else {
+        properties.put(SolrTestCaseJ4.SYSTEM_PROPERTY_SOLR_TESTS_MERGEPOLICYFACTORY, TieredMergePolicyFactory.class.getName());
+        properties.put(SolrTestCaseJ4.SYSTEM_PROPERTY_SOLR_TESTS_USEMERGEPOLICYFACTORY, "true");
+        properties.put(SolrTestCaseJ4.SYSTEM_PROPERTY_SOLR_TESTS_USEMERGEPOLICY, "false");
+      }
       properties.put("solr.tests.mergeScheduler", "org.apache.lucene.index.ConcurrentMergeScheduler");
       properties.put("solr.directoryFactory", "solr.RAMDirectoryFactory");
       createRequest.setProperties(properties);

solr/core/src/test/org/apache/solr/core/TestNRTOpen.java

@@ -23,7 +23,9 @@ import java.util.Set;
 
 import org.apache.lucene.index.LeafReaderContext;
 import org.apache.lucene.index.DirectoryReader;
+import org.apache.lucene.index.LogDocMergePolicy;
 import org.apache.solr.SolrTestCaseJ4;
+import org.apache.solr.index.LogDocMergePolicyFactory;
 import org.apache.solr.search.SolrIndexSearcher;
 import org.apache.solr.util.RefCounted;
 import org.junit.AfterClass;
@@ -39,7 +41,8 @@ public class TestNRTOpen extends SolrTestCaseJ4 {
     System.setProperty("solr.test.leavedatadir", "true");
     // set these so that merges won't break the test
     System.setProperty("solr.tests.maxBufferedDocs", "100000");
-    System.setProperty("solr.tests.mergePolicy", "org.apache.lucene.index.LogDocMergePolicy");
+    systemSetPropertySolrTestsMergePolicy(LogDocMergePolicy.class.getName());
+    systemSetPropertySolrTestsMergePolicyFactory(LogDocMergePolicyFactory.class.getName());
     initCore("solrconfig-basic.xml", "schema-minimal.xml");
     // add a doc
     assertU(adoc("foo", "bar"));
@@ -59,7 +62,8 @@ public class TestNRTOpen extends SolrTestCaseJ4 {
     System.clearProperty("solr.test.leavedatadir");
     System.clearProperty("solr.directoryFactory");
     System.clearProperty("solr.tests.maxBufferedDocs");
-    System.clearProperty("solr.tests.mergePolicy");
+    systemClearPropertySolrTestsMergePolicy();
+    systemClearPropertySolrTestsMergePolicyFactory();
   }
   
   public void setUp() throws Exception {

solr/core/src/test/org/apache/solr/search/TestIndexSearcher.java

@@ -42,11 +42,13 @@ import org.apache.solr.core.SolrCore;
 import org.apache.solr.core.SolrEventListener;
 import org.apache.solr.handler.component.ResponseBuilder;
 import org.apache.solr.handler.component.SearchComponent;
+import org.apache.solr.index.LogDocMergePolicyFactory;
 import org.apache.solr.request.SolrQueryRequest;
 import org.apache.solr.request.SolrRequestHandler;
 import org.apache.solr.schema.SchemaField;
 import org.apache.solr.servlet.DirectSolrConnection;
 import org.apache.solr.util.plugin.SolrCoreAware;
+import org.junit.AfterClass;
 import org.junit.BeforeClass;
 
 public class TestIndexSearcher extends SolrTestCaseJ4 {
@@ -56,11 +58,18 @@ public class TestIndexSearcher extends SolrTestCaseJ4 {
 
     // we need a consistent segmentation because reopen test validation
     // dependso n merges not happening when it doesn't expect
-    System.setProperty("solr.tests.mergePolicy", LogDocMergePolicy.class.getName());
+    systemSetPropertySolrTestsMergePolicy(LogDocMergePolicy.class.getName());
+    systemSetPropertySolrTestsMergePolicyFactory(LogDocMergePolicyFactory.class.getName());
 
     initCore("solrconfig.xml","schema.xml");
   }
   
+  @AfterClass
+  public static void afterClass() {
+    systemClearPropertySolrTestsMergePolicy();
+    systemClearPropertySolrTestsMergePolicyFactory();
+  }
+
   @Override
   public void setUp() throws Exception {
     System.getProperties().remove("tests.solr.useColdSearcher");

solr/core/src/test/org/apache/solr/update/DirectUpdateHandlerTest.java

@@ -32,6 +32,7 @@ import org.apache.solr.common.params.MapSolrParams;
 import org.apache.solr.common.util.NamedList;
 import org.apache.solr.core.SolrCore;
 import org.apache.solr.core.SolrEventListener;
+import org.apache.solr.index.TieredMergePolicyFactory;
 import org.apache.solr.request.LocalSolrQueryRequest;
 import org.apache.solr.request.SolrQueryRequest;
 import org.apache.solr.search.SolrIndexSearcher;
@@ -56,12 +57,15 @@ public class DirectUpdateHandlerTest extends SolrTestCaseJ4 {
     savedFactory = System.getProperty("solr.DirectoryFactory");
     System.setProperty("solr.directoryFactory", "org.apache.solr.core.MockFSDirectoryFactory");
     System.setProperty("enable.update.log", "false"); // schema12 doesn't support _version_
-    System.setProperty("solr.tests.mergePolicy", TieredMergePolicy.class.getName());
+    systemSetPropertySolrTestsMergePolicy(TieredMergePolicy.class.getName());
+    systemSetPropertySolrTestsMergePolicyFactory(TieredMergePolicyFactory.class.getName());
     initCore("solrconfig.xml", "schema12.xml");
   }
   
   @AfterClass
   public static void afterClass() {
+    systemClearPropertySolrTestsMergePolicy();
+    systemClearPropertySolrTestsMergePolicyFactory();
     if (savedFactory == null) {
       System.clearProperty("solr.directoryFactory");
     } else {

solr/core/src/test/org/apache/solr/update/SolrCmdDistributorTest.java

@@ -44,6 +44,7 @@ import org.apache.solr.common.util.NamedList;
 import org.apache.solr.core.CoreContainer;
 import org.apache.solr.core.SolrCore;
 import org.apache.solr.core.SolrEventListener;
+import org.apache.solr.index.LogDocMergePolicyFactory;
 import org.apache.solr.search.SolrIndexSearcher;
 import org.apache.solr.update.MockStreamingSolrClients.Exp;
 import org.apache.solr.update.SolrCmdDistributor.Error;
@@ -51,6 +52,7 @@ import org.apache.solr.update.SolrCmdDistributor.Node;
 import org.apache.solr.update.SolrCmdDistributor.RetryNode;
 import org.apache.solr.update.SolrCmdDistributor.StdNode;
 import org.apache.solr.update.processor.DistributedUpdateProcessor;
+import org.junit.AfterClass;
 import org.junit.BeforeClass;
 import org.junit.Test;
 import org.xml.sax.SAXException;
@@ -63,8 +65,16 @@ public class SolrCmdDistributorTest extends BaseDistributedSearchTestCase {
   public static void beforeClass() throws Exception {
     // we can't use the Randomized merge policy because the test depends on
     // being able to call optimize to have all deletes expunged.
-    System.setProperty("solr.tests.mergePolicy", LogDocMergePolicy.class.getName());
+    systemSetPropertySolrTestsMergePolicy(LogDocMergePolicy.class.getName());
+    systemSetPropertySolrTestsMergePolicyFactory(LogDocMergePolicyFactory.class.getName());
   }
+
+  @AfterClass
+  public static void afterClass() {
+    systemClearPropertySolrTestsMergePolicy();
+    systemClearPropertySolrTestsMergePolicyFactory();
+  }
+
   private UpdateShardHandler updateShardHandler;
   
   public SolrCmdDistributorTest() throws ParserConfigurationException, IOException, SAXException {

solr/test-framework/src/java/org/apache/solr/SolrTestCaseJ4.java

@@ -128,6 +128,16 @@ public abstract class SolrTestCaseJ4 extends LuceneTestCase {
   public static final String DEFAULT_TEST_CORENAME = DEFAULT_TEST_COLLECTION_NAME;
   protected static final String CORE_PROPERTIES_FILENAME = "core.properties";
 
+  // keep solr.tests.mergePolicyFactory use i.e. do not remove with SOLR-8668
+  public static final String SYSTEM_PROPERTY_SOLR_TESTS_MERGEPOLICYFACTORY = "solr.tests.mergePolicyFactory";
+  @Deprecated // remove solr.tests.mergePolicy use with SOLR-8668
+  public static final String SYSTEM_PROPERTY_SOLR_TESTS_MERGEPOLICY = "solr.tests.mergePolicy";
+
+  @Deprecated // remove solr.tests.useMergePolicyFactory with SOLR-8668
+  public static final String SYSTEM_PROPERTY_SOLR_TESTS_USEMERGEPOLICYFACTORY = "solr.tests.useMergePolicyFactory";
+  @Deprecated // remove solr.tests.useMergePolicy use with SOLR-8668
+  public static final String SYSTEM_PROPERTY_SOLR_TESTS_USEMERGEPOLICY = "solr.tests.useMergePolicy";
+
   private static String coreName = DEFAULT_TEST_CORENAME;
 
   public static int DEFAULT_CONNECTION_TIMEOUT = 60000;  // default socket connection timeout in ms
@@ -2077,4 +2087,39 @@ public abstract class SolrTestCaseJ4 extends LuceneTestCase {
     registeredSearcher.decref();
     newestSearcher.decref();
   }
+
+  @BeforeClass
+  public static void chooseMPForMP() throws Exception {
+    if (random().nextBoolean()) {
+      System.setProperty(SYSTEM_PROPERTY_SOLR_TESTS_USEMERGEPOLICYFACTORY, "true");
+      System.setProperty(SYSTEM_PROPERTY_SOLR_TESTS_USEMERGEPOLICY, "false");
+    } else {
+      System.setProperty(SYSTEM_PROPERTY_SOLR_TESTS_USEMERGEPOLICYFACTORY, "false");
+      System.setProperty(SYSTEM_PROPERTY_SOLR_TESTS_USEMERGEPOLICY, "true");
+    }
+  }
+
+  @AfterClass
+  public static void unchooseMPForMP() {
+    System.clearProperty(SYSTEM_PROPERTY_SOLR_TESTS_USEMERGEPOLICYFACTORY);
+    System.clearProperty(SYSTEM_PROPERTY_SOLR_TESTS_USEMERGEPOLICY);
+  }
+
+  @Deprecated // remove with SOLR-8668
+  protected static void systemSetPropertySolrTestsMergePolicy(String value) {
+    System.setProperty(SYSTEM_PROPERTY_SOLR_TESTS_MERGEPOLICY, value);
+  }
+
+  @Deprecated // remove with SOLR-8668
+  protected static void systemClearPropertySolrTestsMergePolicy() {
+    System.clearProperty(SYSTEM_PROPERTY_SOLR_TESTS_MERGEPOLICY);
+  }
+
+  protected static void systemSetPropertySolrTestsMergePolicyFactory(String value) {
+    System.setProperty(SYSTEM_PROPERTY_SOLR_TESTS_MERGEPOLICYFACTORY, value);
+  }
+
+  protected static void systemClearPropertySolrTestsMergePolicyFactory() {
+    System.clearProperty(SYSTEM_PROPERTY_SOLR_TESTS_MERGEPOLICYFACTORY);
+  }
 }