public void MoreThan20ResultShouldOnlyReturn20Records(
double[] expectedNpvResult, decimal lowerDiscount, decimal upperDiscount,
decimal increment, decimal outflow, double[] inflows)
{
var sut = new NpvCalculator();
//Validation has been tested on project NpvApi.Dtos.Test so will not test again here.
var npvOptions = new NpvOptions
{
RateOption = new RateOption
{
LowerDiscount = lowerDiscount,
UpperDiscount = upperDiscount,
DiscountIncrement = increment
},
Outflow = outflow
};
foreach (var inflow in inflows.ToList())
{
npvOptions.Inflows.Add(new Inflow()
{
Value = (decimal)inflow
});
}
var result = sut.Calculate(npvOptions);
Assert.Equal(20, result.Count);
}
public IActionResult Post([FromBody] NpvOptions npvOptions)
{
if (!ModelState.IsValid)
{
return(BadRequest(ModelState));
}
var result = _nvpCalculator.Calculate(npvOptions);
return(Ok(result));
}
public IList <NpvResult> Calculate(NpvOptions options)
{
decimal lowerDiscount = options.RateOption.LowerDiscount;
decimal upperDiscount = options.RateOption.UpperDiscount;
decimal increment = options.RateOption.DiscountIncrement;
decimal initialOutflow = -options.Outflow;
var inflows = options.Inflows.Select(i => i.Value).ToList();
var result = new List <NpvResult>();
int loopCount = 0;
do
{
var npv = (double)initialOutflow;
for (int i = 0; i < inflows.Count(); i++)
{
var denom = Math.Pow((1 + (double)lowerDiscount / 100), i + 1);
npv += (double)inflows[i] / denom;
}
result.Add(new NpvResult()
{
DiscountRate = lowerDiscount,
//Round result to 2 digits
NetPresentValue = (decimal)Math.Round(npv, 2)
});
lowerDiscount += increment;
//The max results we will return to user to prevent
//malicious user putting some edge case input to make calculation do very long loop
loopCount++;
if (loopCount >= MaxLoopCount)
{
break;
}
//If increment = 0 means user only want to calculate one result instead of serial of results
//In this case normally should set lowerDiscount = higherDiscount, but user specify
//different value for lower or higherDiscount we just assume we will use the lowerDiscount
//and make sure we break out of the loop. Negtive should already been checked by ValidationAttribute and should never happen.
if (increment <= 0)
{
break;
}
}while (lowerDiscount <= upperDiscount);
return(result);
}
public void InvalidInputShouldReturnBadRequestStatusWithModelErrors(double[] expectedNpvResult,
decimal lowerDiscount, decimal upperDiscount, decimal increment, decimal outflow,
double[] inflows)
{
//Arrange
var stubCalculator = Substitute.For <INpvCalculator>();
var controller = new NpvController(stubCalculator);
//Validation testing has been done on project NpvApi.Dtos.Test so will not test again here.
var npvOptions = new NpvOptions
{
RateOption = new RateOption
{
LowerDiscount = lowerDiscount,
UpperDiscount = upperDiscount
},
Outflow = outflow
};
foreach (var inflow in inflows.ToList())
{
npvOptions.Inflows.Add(new Inflow()
{
Value = (decimal)inflow
});
}
const string errorPropertyKey = "UpperDiscount";
const string errorPropertyValue = "Required";
//Add the error to model state to mock 400 BadRequest
controller.ModelState.AddModelError(errorPropertyKey, errorPropertyValue);
//Act
var actionResult = controller.Post(npvOptions);
var badRequestResult = actionResult as BadRequestObjectResult;
//Assert response should contain the model errors
Assert.NotNull(badRequestResult);
Assert.Equal(400, badRequestResult.StatusCode);
var responseContent = badRequestResult.Value as SerializableError;
Assert.NotNull(responseContent);
Assert.Equal(1, responseContent.Keys.Count);
Assert.Equal(errorPropertyKey, responseContent.Keys.First());
Assert.Equal(errorPropertyValue, (responseContent.Values.First() as string[]).First());
}
public void ValidInputShouldCallApplicationServiceWithCorrectDataAndReturnOk(double[] expectedNpvResult,
decimal lowerDiscount, decimal upperDiscount, decimal increment, decimal outflow,
double[] inflows)
{
//Autofixture does not support Asp.net Core so can not use AutoData for
//NSubstitute and just use InlineData instead
var mockCalculator = Substitute.For <INpvCalculator>();
var controller = new NpvController(mockCalculator);
//Validation testing has been done on project NpvApi.Dtos.Test so will not test again here.
var npvOptions = new NpvOptions
{
RateOption = new RateOption
{
LowerDiscount = lowerDiscount,
UpperDiscount = upperDiscount
},
Outflow = outflow
};
foreach (var inflow in inflows.ToList())
{
npvOptions.Inflows.Add(new Inflow()
{
Value = (decimal)inflow
});
}
var actionResult = controller.Post(npvOptions);
mockCalculator.Received().Calculate(npvOptions);
var badRequestResult = actionResult as OkObjectResult;
//Assert response should contain the model errors
Assert.NotNull(badRequestResult);
Assert.Equal(200, badRequestResult.StatusCode);
}
public void ValidInputShouldGetCorrectNpvResults(double[] expectedNpvResult,
decimal lowerDiscount, decimal upperDiscount, decimal increment, decimal outflow,
double[] inflows)
{
var sut = new NpvCalculator();
//Validation testing has been done on project NpvApi.Dtos.Test so will not test again here.
var npvOptions = new NpvOptions
{
RateOption = new RateOption
{
LowerDiscount = lowerDiscount,
UpperDiscount = upperDiscount,
DiscountIncrement = increment
},
Outflow = outflow
};
foreach (var inflow in inflows.ToList())
{
npvOptions.Inflows.Add(new Inflow()
{
Value = (decimal)inflow
});
}
var result = sut.Calculate(npvOptions);
Assert.Equal(expectedNpvResult.Length, result.Count);
for (int i = 0; i < expectedNpvResult.Length; i++)
{
var expected = expectedNpvResult[i];
var actual = (double)result[i].NetPresentValue;
Assert.Equal(expected, actual);
}
}
public void RateIncrement0ShouldOnlyReturn1ResultBack(
double[] expectedNpvResult, decimal lowerDiscount, decimal upperDiscount,
decimal increment, decimal outflow, double[] inflows)
{
//This case need to check the result set which is different than the previous one\
//so just keep it seperate.
var sut = new NpvCalculator();
var npvOptions = new NpvOptions
{
RateOption = new RateOption
{
LowerDiscount = lowerDiscount,
UpperDiscount = upperDiscount,
DiscountIncrement = increment
},
Outflow = outflow
};
foreach (var inflow in inflows.ToList())
{
npvOptions.Inflows.Add(new Inflow()
{
Value = (decimal)inflow
});
}
var result = sut.Calculate(npvOptions);
Assert.Equal(1, result.Count);
var expected = expectedNpvResult.First();
var actual = (double)result.First().NetPresentValue;
Assert.Equal(expected, actual);
}
