src/net/instaweb/util/write_through_cache_test.cc

/**
 * Copyright 2010 Google Inc.
 *
 * 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
 *
 *      http://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.
 */

// Author: jmarantz@google.com (Joshua Marantz)

// Unit-test the write-through cache

#include "net/instaweb/util/public/write_through_cache.h"

#include "base/basictypes.h"
#include "base/logging.h"
#include "net/instaweb/util/public/gtest.h"
#include "net/instaweb/util/public/lru_cache.h"
#include "net/instaweb/util/public/shared_string.h"
#include <string>

namespace net_instaweb {

class WriteThroughCacheTest : public testing::Test {
 protected:
  WriteThroughCacheTest()
      : small_cache_(new LRUCache(15)),
        big_cache_(new LRUCache(1000)),
        write_through_cache_(small_cache_, big_cache_) {
  }

  void CheckGet(CacheInterface* cache, const char* key,
                const std::string& expected_value) {
    SharedString value_buffer;
    EXPECT_TRUE(cache->Get(key, &value_buffer));
    EXPECT_EQ(expected_value, *value_buffer);
    EXPECT_EQ(CacheInterface::kAvailable, cache->Query(key));
  }

  void Put(const char* key, const char* value) {
    SharedString put_buffer(value);
    write_through_cache_.Put(key, &put_buffer);
  }

  void CheckNotFound(CacheInterface* cache, const char* key) {
    SharedString value_buffer;
    EXPECT_FALSE(cache->Get(key, &value_buffer));
    EXPECT_EQ(CacheInterface::kNotFound, cache->Query(key));
  }

  LRUCache* small_cache_;
  LRUCache* big_cache_;
  WriteThroughCache write_through_cache_;

 private:
  DISALLOW_COPY_AND_ASSIGN(WriteThroughCacheTest);
};

// Simple flow of putting in an item, getting it, deleting it.
TEST_F(WriteThroughCacheTest, PutGetDelete) {
  // First, put some small data into the write-through.  It should
  // be available in both caches.
  Put("Name", "Value");
  CheckGet(&write_through_cache_, "Name", "Value");
  CheckGet(small_cache_, "Name", "Value");
  CheckGet(big_cache_, "Name", "Value");

  CheckNotFound(&write_through_cache_, "Another Name");

  // next, put another value in.  This will evict the first item
  // out of the small cache,
  Put("Name2", "NewValue");
  CheckGet(&write_through_cache_, "Name2", "NewValue");
  CheckGet(small_cache_, "Name2", "NewValue");
  CheckGet(big_cache_, "Name2", "NewValue");

  // The first item will still be available in the write-through,
  // and in the big-cache, but will have been evicted from the
  // small cache.
  CheckNotFound(small_cache_, "Name");
  CheckGet(big_cache_, "Name", "Value");
  CheckNotFound(small_cache_, "Name");

  CheckGet(&write_through_cache_, "Name", "Value");

  // But now, once we've gotten in out of the write-through cache,
  // the small cache will have the value "freshened."
  CheckGet(small_cache_, "Name", "Value");

  write_through_cache_.Delete("Name2");
  CheckNotFound(&write_through_cache_, "Name2");
  CheckNotFound(small_cache_, "Name2");
  CheckNotFound(big_cache_, "Name2");
}

// Check size-limits for the small cache
TEST_F(WriteThroughCacheTest, SizeLimit) {
  write_through_cache_.set_cache1_limit(10);

  // This one will fit.
  Put("Name", "Value");
  CheckGet(&write_through_cache_, "Name", "Value");
  CheckGet(small_cache_, "Name", "Value");
  CheckGet(big_cache_, "Name", "Value");

  // This one will not.
  Put("Name2", "TooBig");
  CheckGet(&write_through_cache_, "Name2", "TooBig");
  CheckNotFound(small_cache_, "Name2");
  CheckGet(big_cache_, "Name2", "TooBig");

  // However "Name" is still in both caches.
  CheckGet(small_cache_, "Name", "Value");
  CheckGet(&write_through_cache_, "Name", "Value");
  CheckGet(big_cache_, "Name", "Value");
}

}  // namespace net_instaweb