Fix search test NPE

src/main/java/org/jabref/logic/search/DatabaseSearcher.java

@@ -37,14 +37,15 @@ public List<BibEntry> getMatches() {
 
         if (!query.isValid()) {
             LOGGER.warn("Search failed: invalid search expression");
+            luceneManager.closeAndWait();
             return Collections.emptyList();
         }
         List<BibEntry> matchEntries = luceneManager.search(query)
                                                    .getMatchedEntries()
                                                    .stream()
                                                    .map(entryId -> databaseContext.getDatabase().getEntryById(entryId))
                                                    .toList();
-        luceneManager.close();
+        luceneManager.closeAndWait();
         return BibDatabases.purgeEmptyEntries(matchEntries);
     }
 }

src/main/java/org/jabref/logic/search/LuceneManager.java

@@ -210,6 +210,13 @@ public void close() {
         databaseContext.getDatabase().postEvent(new IndexClosedEvent());
     }
 
+    public void closeAndWait() {
+        bibFieldsIndexer.closeAndWait();
+        shouldIndexLinkedFiles.removeListener(preferencesListener);
+        linkedFilesIndexer.closeAndWait();
+        databaseContext.getDatabase().postEvent(new IndexClosedEvent());
+    }
+
     public AutoCloseable blockLinkedFileIndexer() {
         LOGGER.debug("Blocking linked files indexer");
         isLinkedFilesIndexerBlocked.set(true);

src/main/java/org/jabref/logic/search/indexing/BibFieldsIndexer.java

@@ -156,6 +156,11 @@ public void close() {
         HeadlessExecutorService.INSTANCE.execute(this::closeIndex);
     }
 
+    @Override
+    public void closeAndWait() {
+        HeadlessExecutorService.INSTANCE.executeAndWait(this::closeIndex);
+    }
+
     private void closeIndex() {
         try {
             LOGGER.debug("Closing bib fields index");

src/main/java/org/jabref/logic/search/indexing/DefaultLinkedFilesIndexer.java

@@ -315,6 +315,11 @@ public void close() {
         HeadlessExecutorService.INSTANCE.execute(this::closeIndex);
     }
 
+    @Override
+    public void closeAndWait() {
+        HeadlessExecutorService.INSTANCE.executeAndWait(this::closeIndex);
+    }
+
     private void closeIndex() {
         try {
             LOGGER.debug("Closing linked files index");

src/main/java/org/jabref/logic/search/indexing/ReadOnlyLinkedFilesIndexer.java

@@ -63,6 +63,11 @@ public void close() {
         HeadlessExecutorService.INSTANCE.execute(this::closeIndex);
     }
 
+    @Override
+    public void closeAndWait() {
+        HeadlessExecutorService.INSTANCE.executeAndWait(this::closeIndex);
+    }
+
     private void closeIndex() {
         try {
             searcherManager.close();

src/main/java/org/jabref/model/search/LuceneIndexer.java

@@ -23,4 +23,6 @@ public interface LuceneIndexer {
     SearcherManager getSearcherManager();
 
     void close();
+
+    void closeAndWait();
 }

src/test/java/org/jabref/logic/search/DatabaseSearcherTest.java

@@ -1,6 +1,7 @@
 package org.jabref.logic.search;
 
 import java.io.IOException;
+import java.nio.file.Path;
 import java.util.EnumSet;
 import java.util.List;
 import java.util.stream.Stream;
@@ -18,24 +19,29 @@
 import org.jabref.preferences.FilePreferences;
 
 import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.io.TempDir;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.Arguments;
 import org.junit.jupiter.params.provider.MethodSource;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.spy;
 import static org.mockito.Mockito.when;
 
 public class DatabaseSearcherTest {
     private static final TaskExecutor TASK_EXECUTOR = new CurrentThreadTaskExecutor();
     private BibDatabaseContext databaseContext;
     private final FilePreferences filePreferences = mock(FilePreferences.class);
+    @TempDir
+    private Path indexDir;
 
     @BeforeEach
     void setUp() {
         when(filePreferences.shouldFulltextIndexLinkedFiles()).thenReturn(false);
         when(filePreferences.fulltextIndexLinkedFilesProperty()).thenReturn(mock(BooleanProperty.class));
-        databaseContext = new BibDatabaseContext();
+        databaseContext = spy(new BibDatabaseContext());
+        when(databaseContext.getFulltextIndexPath()).thenReturn(indexDir);
     }
 
     @ParameterizedTest

src/test/java/org/jabref/logic/search/DatabaseSearcherWithBibFilesTest.java

@@ -33,6 +33,7 @@
 
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.spy;
 import static org.mockito.Mockito.when;
 
 class DatabaseSearcherWithBibFilesTest {
@@ -77,7 +78,8 @@ private BibDatabaseContext initializeDatabaseFromPath(String testFile) throws Ex
 
     private BibDatabaseContext initializeDatabaseFromPath(Path testFile) throws Exception {
         ParserResult result = new BibtexImporter(mock(ImportFormatPreferences.class, Answers.RETURNS_DEEP_STUBS), new DummyFileUpdateMonitor()).importDatabase(testFile);
-        BibDatabaseContext databaseContext = result.getDatabaseContext();
+        BibDatabaseContext databaseContext = spy(result.getDatabaseContext());
+        when(databaseContext.getFulltextIndexPath()).thenReturn(indexDir);
 
         when(filePreferences.shouldFulltextIndexLinkedFiles()).thenReturn(true);
         when(filePreferences.fulltextIndexLinkedFilesProperty()).thenReturn(new SimpleBooleanProperty(true));