refactor: Make tests composable

Inherits the gtest test virtually to llow combining test base classes.
Allows specifying an extrermal path for LocalRunnerTestBase.

Author: Orri Erling

velox/exec/tests/utils/LocalRunnerTestBase.cpp

@@ -60,7 +60,7 @@ void LocalRunnerTestBase::setupConnector() {
   connector::unregisterConnector(kHiveConnectorId);
 
   std::unordered_map<std::string, std::string> configs;
-  configs[connector::hive::HiveConfig::kLocalDataPath] = files_->getPath();
+  configs[connector::hive::HiveConfig::kLocalDataPath] = testDataPath_;
   configs[connector::hive::HiveConfig::kLocalFileFormat] = "dwrf";
   auto hiveConnector =
       connector::getConnectorFactory(
@@ -75,9 +75,16 @@ void LocalRunnerTestBase::setupConnector() {
 void LocalRunnerTestBase::makeTables(
     std::vector<TableSpec> specs,
     std::shared_ptr<TempDirectoryPath>& directory) {
-  directory = exec::test::TempDirectoryPath::create();
+  if (initialized_) {
+    return;
+  }
+  initialized_ = true;
+  if (testDataPath_.empty()) {
+    directory = exec::test::TempDirectoryPath::create();
+    testDataPath_ = directory->getPath();
+  }
   for (auto& spec : specs) {
-    auto tablePath = fmt::format("{}/{}", directory->getPath(), spec.name);
+    auto tablePath = fmt::format("{}/{}", testDataPath_, spec.name);
     auto fs = filesystems::getFileSystem(tablePath, {});
     fs->mkdir(tablePath);
     for (auto i = 0; i < spec.numFiles; ++i) {

velox/exec/tests/utils/LocalRunnerTestBase.h

@@ -47,6 +47,7 @@ class LocalRunnerTestBase : public HiveConnectorTestBase {
   }
 
   static void TearDownTestCase() {
+    initialized_ = false;
     files_.reset();
     HiveConnectorTestBase::TearDownTestCase();
   }
@@ -84,6 +85,8 @@ class LocalRunnerTestBase : public HiveConnectorTestBase {
   inline static std::vector<TableSpec> testTables_;
 
   // The top level directory with the test data.
+  inline static bool initialized_;
+  inline static std::string testDataPath_;
   inline static std::shared_ptr<TempDirectoryPath> files_;
   /// Map from table name to list of file system paths.
   inline static std::unordered_map<std::string, std::vector<std::string>>

velox/exec/tests/utils/OperatorTestBase.h

@@ -28,7 +28,7 @@
 #include "velox/vector/tests/utils/VectorTestBase.h"
 
 namespace facebook::velox::exec::test {
-class OperatorTestBase : public testing::Test,
+class OperatorTestBase : public virtual testing::Test,
                          public velox::test::VectorTestBase {
  public:
   /// The following methods are used by google unit test framework to do