Implemented submittable_executor and some other missed files

A file was named wrong. It was changed.

internal/platform/implementation/linux/thread_pool_test.cc

@@ -0,0 +1,71 @@
+// Copyright 2022 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "internal/platform/implementation/linux/thread_pool.h"
+
+#include <vector>
+
+#include "gtest/gtest.h"
+#include "absl/synchronization/blocking_counter.h"
+#include "absl/synchronization/notification.h"
+#include "absl/time/clock.h"
+#include "absl/time/time.h"
+
+namespace nearby {
+namespace linux {
+namespace {
+
+constexpr int kTaskCount = 10;
+
+TEST(ThreadPool, TasksInSingleThreadRunInSequence) {
+  absl::BlockingCounter blocking_counter(kTaskCount);
+  auto pool = ThreadPool::Create(1);
+  std::vector<int> completed_tasks;
+  std::vector<int> expected_tasks;
+
+  for (int i = 0; i < kTaskCount; ++i) {
+    expected_tasks.push_back(i);
+    pool->Run([&, i]() {
+      absl::SleepFor(absl::Milliseconds(200));
+      completed_tasks.push_back(i);
+      blocking_counter.DecrementCount();
+    });
+  }
+
+  blocking_counter.Wait();
+  EXPECT_EQ(completed_tasks, expected_tasks);
+  pool->ShutDown();
+}
+
+TEST(ThreadPool, TasksInMultipleThreadsRunInParallel) {
+  absl::BlockingCounter blocking_counter(kTaskCount);
+  absl::Time start_time = absl::Now();
+
+  auto pool = ThreadPool::Create(2);
+
+  for (int i = 0; i < kTaskCount; ++i) {
+    pool->Run([&]() {
+      absl::SleepFor(absl::Milliseconds(200));
+      blocking_counter.DecrementCount();
+    });
+  }
+
+  blocking_counter.Wait();
+  EXPECT_TRUE(absl::Now() - start_time < absl::Milliseconds(1500));
+  pool->ShutDown();
+}
+
+}  // namespace
+}  // namespace linux
+}  // namespace nearby