@Nullable
  public static PsiClass[] getAllTestClasses(final TestClassFilter filter, boolean sync) {
    final PsiClass[][] holder = new PsiClass[1][];
    final Runnable process =
        () -> {
          final ProgressIndicator indicator = ProgressManager.getInstance().getProgressIndicator();

          final Collection<PsiClass> set = new LinkedHashSet<>();
          final PsiManager manager = PsiManager.getInstance(filter.getProject());
          final GlobalSearchScope projectScope =
              GlobalSearchScope.projectScope(manager.getProject());
          final GlobalSearchScope scope = projectScope.intersectWith(filter.getScope());
          for (final PsiClass psiClass : AllClassesSearch.search(scope, manager.getProject())) {
            if (filter.isAccepted(psiClass)) {
              if (indicator != null) {
                indicator.setText2(
                    "Found test class " + ReadAction.compute(psiClass::getQualifiedName));
              }
              set.add(psiClass);
            }
          }
          holder[0] = set.toArray(new PsiClass[set.size()]);
        };
    if (sync) {
      ProgressManager.getInstance()
          .runProcessWithProgressSynchronously(
              process, "Searching For Tests...", true, filter.getProject());
    } else {
      process.run();
    }
    return holder[0];
  }
  @NotNull
  @Override
  public GlobalSearchScope restrictByBackwardIds(
      @NotNull final VirtualFile virtualFile, @NotNull GlobalSearchScope scope) {
    final int[] backIds =
        RefResolveService.getInstance(myProject).getBackwardIds((VirtualFileWithId) virtualFile);
    if (backIds == null) {
      return scope;
    }
    String files = toVfString(backIds);
    String log = "Restricting scope of " + virtualFile.getName() + " to " + files;
    if (!log.equals(prevLog)) {
      log(log);
      flushLog();
      prevLog = log;
    }
    GlobalSearchScope restrictedByBackwardIds =
        new GlobalSearchScope() {
          @Override
          public boolean contains(@NotNull VirtualFile file) {
            if (!(file instanceof VirtualFileWithId)
                || file.equals(virtualFile)
                || ArrayUtil.indexOf(backIds, getAbsId(file)) != -1) return true;
            return false
                & !myProjectFileIndex.isUnderSourceRootOfType(
                    file,
                    SOURCE_ROOTS); // filter out source file which we know for sure does not
                                   // reference the element
          }

          @Override
          public int compare(@NotNull VirtualFile file1, @NotNull VirtualFile file2) {
            return 0;
          }

          @Override
          public boolean isSearchInModuleContent(@NotNull Module aModule) {
            return true;
          }

          @Override
          public boolean isSearchInLibraries() {
            return false;
          }
        };
    return scope.intersectWith(restrictedByBackwardIds);
  }
  @NotNull
  private Object[] getSubclassVariants(
      @NotNull PsiPackage context, @NotNull String[] extendClasses) {
    HashSet<Object> lookups = new HashSet<Object>();
    GlobalSearchScope packageScope = PackageScope.packageScope(context, true);
    GlobalSearchScope scope = myJavaClassReferenceSet.getProvider().getScope();
    if (scope != null) {
      packageScope = packageScope.intersectWith(scope);
    }
    final GlobalSearchScope allScope = ProjectScope.getAllScope(context.getProject());
    final boolean instantiatable =
        JavaClassReferenceProvider.INSTANTIATABLE.getBooleanValue(getOptions());
    final boolean notInterface =
        JavaClassReferenceProvider.NOT_INTERFACE.getBooleanValue(getOptions());
    final boolean notEnum = JavaClassReferenceProvider.NOT_ENUM.getBooleanValue(getOptions());
    final boolean concrete = JavaClassReferenceProvider.CONCRETE.getBooleanValue(getOptions());

    final ClassKind classKind = getClassKind();

    for (String extendClassName : extendClasses) {
      final PsiClass extendClass =
          JavaPsiFacade.getInstance(context.getProject()).findClass(extendClassName, allScope);
      if (extendClass != null) {
        // add itself
        if (packageScope.contains(extendClass.getContainingFile().getVirtualFile())) {
          if (isClassAccepted(
              extendClass, classKind, instantiatable, concrete, notInterface, notEnum)) {
            ContainerUtil.addIfNotNull(createSubclassLookupValue(context, extendClass), lookups);
          }
        }
        for (final PsiClass clazz : ClassInheritorsSearch.search(extendClass, packageScope, true)) {
          if (isClassAccepted(clazz, classKind, instantiatable, concrete, notInterface, notEnum)) {
            ContainerUtil.addIfNotNull(createSubclassLookupValue(context, clazz), lookups);
          }
        }
      }
    }
    return lookups.toArray();
  }