public void GetAll_ShouldThrowException_WhenSortOrderIsEmpty()
        {
            // Arrange
            var sortOrder = string.Empty;
            var symbols   = new string[] { "BTC", "ETH" };

            _mockCryptoLogic
            .Setup(repo => repo.GetSymbols(It.IsAny <string>(), It.IsAny <string>(), sortOrder))
            .Returns(symbols);

            // Act
            var result = _target.GetAll(sortOrder);

            // Assert
            Assert.IsType <BadRequestObjectResult>(result);
        }