public async Task AddEntity()
        {
            // Arrange
            const long   longValue   = 555;
            const string stringValue = "555";
            var          entity      = new Poco
            {
                LongValue   = longValue,
                StringValue = stringValue
            };

            // Act
            Poco result = await _repository.AddAsync(entity);

            // Assert
            Assert.Equal(longValue, result.LongValue);
            Assert.Equal(stringValue, result.StringValue);
            Assert.NotEqual(null, result.Id);
        }
        public async Task First()
        {
            // Arrange
            List <Poco> entities = Enumerable.Range(0, 5).Select(p => new Poco
            {
                LongValue   = p,
                StringValue = p.ToString(CultureInfo.InvariantCulture)
            }).ToList();

            await _repository.AddAsync(entities);

            // Act
            Poco result = await _repository.FirstAsync();

            // Assert
            Assert.NotNull(result);
            Assert.Equal(entities[0].Id, result.Id);
            Assert.Equal(entities[0].LongValue, result.LongValue);
            Assert.Equal(entities[0].StringValue, result.StringValue);
        }