avoid synchronous index rebuild in tests to avoid problems with read action at hand

platform/lang-impl/src/com/intellij/util/indexing/FileBasedIndexImpl.java

@@ -1210,6 +1210,10 @@ public class FileBasedIndexImpl extends FileBasedIndex {
 
   @Nullable
   public static Throwable getCauseToRebuildIndex(@NotNull RuntimeException e) {
+    if (ApplicationManager.getApplication().isUnitTestMode()) {
+      // avoid rebuilding index in tests since we do it synchronously in requestRebuild and we can have readAction at hand
+      return null;
+    }
     if (e instanceof IndexOutOfBoundsException) return e; // something wrong with direct byte buffer
     Throwable cause = e.getCause();
     if (cause instanceof StorageException || cause instanceof IOException ||