Question

Is there a way of testing functions inside a class in an easy way for correct results? I mean, I have been looking at google test unit testing, but seems more to find fails in the work classes and functions, more than in the expected result.

For example, from math theory one could know which is the square root of all numbers, now you want to check a sqrt function, seeking for floating point precision errors, and then you also want to check lot of functions that use floats and look for any precision error, is there a way to make this easy and fast ?

Answer 1

I can think of 2 direct solutions

1)

one of the easiest ways to test for accuracy of mathematical functions is similar to what is used as definition work for limits in calculus. taking the value to be tested, and then also using a value that is “close” on both sides. I have heard of analogies drawn between limit analysis and unit testing, but keep in mind that if your looking for speed this will not be your best options. and that this will only work on continues operations, and that this analogy is for definition work only

so what you would do is have a “limitDomain” variable defined per function (this is because some operations are more accurate then others for reasoning look up taylor approximation of [function]), and then use that as you limiter. then test: low, high, and then the value itself, and then take the avg of all three within a given margin of error,

float testMathOpX(float _input){
    float low = 0.0f;
    float high = 0.0f;

    low = _input - limitDomainOpX;
    high = _input + limitDomainOpX;

    low = OpX(low);
    _input = OpX(_input);
    high = OpX(high);

    // doing 3 separate averages with division by 2 mains the worst decimal you will have is a trailing 5, or in some cases a trailing 25
    low = (low + _input)/2
    high = (_input + high)/2;
    _input = (low + high)/2
    return _input;
}

2)

the other method that I can think of is more of a table of values approach being that you take the input, and then check to see where on the domain of the operation it lies, and if it lies within certain values then you use value replacement. The thing to realize is that you need to have a lot of work ahead of time to get these table of values, and then it becomes just domain testing of the value your taking in in the form of:

if( (_input > valLow) && (_input < valHigh)){
     ... replace the value with an empirically found value
}

the problem with this is that you need o find those empirically found values.