public PricesMongoDbPersistenceTest()
        {
            var MONGO_ENABLED      = Environment.GetEnvironmentVariable("MONGO_ENABLED") ?? "true";
            var MONGO_DB           = Environment.GetEnvironmentVariable("MONGO_DB") ?? "test";
            var MONGO_COLLECTION   = Environment.GetEnvironmentVariable("MONGO_COLLECTION") ?? "price";
            var MONGO_SERVICE_HOST = Environment.GetEnvironmentVariable("MONGO_SERVICE_HOST") ?? "localhost";
            var MONGO_SERVICE_PORT = Environment.GetEnvironmentVariable("MONGO_SERVICE_PORT") ?? "27017";
            var MONGO_SERVICE_URI  = Environment.GetEnvironmentVariable("MONGO_SERVICE_URI");

            _enabled = BooleanConverter.ToBoolean(MONGO_ENABLED);

            if (_enabled)
            {
                var config = ConfigParams.FromTuples(
                    "collection", MONGO_COLLECTION,
                    "connection.database", MONGO_DB,
                    "connection.host", MONGO_SERVICE_HOST,
                    "connection.port", MONGO_SERVICE_PORT,
                    "connection.uri", MONGO_SERVICE_URI
                    );

                _persistence = new PricesMongoDbPersistence();
                _persistence.Configure(config);
                _persistence.OpenAsync(null).Wait();
                _persistence.ClearAsync(null).Wait();

                _fixture = new PricesPersistenceFixture(_persistence);
            }
        }
        public PricesMemoryPersistenceTest()
        {
            _persistence = new PricesMemoryPersistence();
            _persistence.Configure(new ConfigParams());

            _fixture = new PricesPersistenceFixture(_persistence);

            _persistence.OpenAsync(null).Wait();
        }
        public PricesFilePersistenceTest()
        {
            ConfigParams config = ConfigParams.FromTuples(
                "path", "prices.json"
                );

            _persistence = new PricesFilePersistence();
            _persistence.Configure(config);
            _persistence.OpenAsync(null).Wait();
            _persistence.ClearAsync(null).Wait();

            _fixture = new PricesPersistenceFixture(_persistence);
        }