Formatting a data set - testcases/method for making sure it is correct

this is my dataset

dfg=[[{"key":"Product_Description","value":"$100.83 Business Select Plan excl GST"},{"key":">20MB/30","value":1480},{"key":">200MB/30","value":1234},{"key":">2048MB/30","value":697},{"key":">5120MB/30","value":379},{"key":">10240MB/30","value":174}],[{"key":"Product_Description","value":"$119.95 Business Share Everything Plan"},{"key":">20MB/30","value":66},{"key":">200MB/30","value":57},{"key":">2048MB/30","value":30},{"key":">5120MB/30","value":14},{"key":">10240MB/30","value":6}]]

THis is my function:

function format_data_to_percent(d){

    var data = d
    data.map(function(a){ 
        var sum = a.slice(1).map(function(a){ return a.value; }).reduce(function(a,b){return a*1+b*1},0); 
        //console.log("sum",sum); 

        a.slice(1).filter(function(a){
            //console.log(a)
            a.value=a.value/sum
            //console.log(a)
        }); 

        return a;
    })

    //START TEST 
    //END TEST 
        return data
}

What I am trying to do is get the percentage value for example I first get the values in each element

dfg[0].slice(1).map(function(a){ return a.value; })
[1480, 1234, 697, 379, 174]

Then I use the reduce function to sum this array:

dfg[0].slice(1).map(function(a){ return a.value; }).reduce(function(a,b){return a*1+b*1},0);
3964

I then do a slice and filter on the values and the divide them by the sum

dfg[0].slice(1).filter(function(a){            
  console.log(a)
  console.log(a.value)
  console.log(sum)
  a.value=a.value/sum 
  //console.log(a)
}); 

this then gives me dfg after manipulating the first element

[[{"key":"Product_Description","value":"$100.83 Business Select Plan excl GST"},
    {"key":">20MB/30","value":0.37336024217961655},
    {"key":">200MB/30","value":0.3113017154389506},
    {"key":">2048MB/30","value":0.17583249243188698},
    {"key":">5120MB/30","value":0.09561049445005046},
    {"key":">10240MB/30","value":0.04389505549949546}],
    [{"key":"Product_Description","value":"$119.95 Business Share Everything Plan"},
        {"key":">20MB/30","value":66},
        {"key":">200MB/30","value":57},
        {"key":">2048MB/30","value":30},
        {"key":">5120MB/30","value":14},
        {"key":">10240MB/30","value":6}]]

This gives me the result that I want

> 1480/3964
0.37336024217961655
> 1234/3964
0.3113017154389506
> 697/3964
0.17583249243188698
> 379/3964
0.09561049445005046
> 174/3964
0.04389505549949546
>

What I am looking for is a way to test this for a bigger dataset ot make sure the results are as expected always.Can anyone advise?

I have tried something like this

//START TEST 
// create a test case for it //amke this better
vals=data_p[0].slice(1).map(function(a){ return a.value; })
//["11", "33", "10", "55", "10"]
console.log("vals",vals)
sum = data_p[0].slice(1).map(function(a){ return a.value; }).reduce(function(a,b){return a*1+b*1},0);
//119
vals2=vals.map(function(a){ return a/sum})
//[0.09243697478991597, 0.2773109243697479, 0.08403361344537816, 0.46218487394957986, 0.08403361344537816]

console.log(data[0][1].value)
console.log(data[0][2].value)
console.log(data[0][3].value)
console.log(data[0][4].value)
console.log(data[0][5].value)
console.log(vals2[0])
console.log(vals2[1])
console.log(vals2[2])
console.log(vals2[3])
console.log(vals2[4])
console.log("test1\-\-> ",data[0][1].value == vals2[0])
console.log("test2\-\> ",data[0][2].value == vals2[1])
console.log("test3\-\> ",data[0][3].value == vals2[2])
console.log("test4\-\> ",data[0][4].value == vals2[3])
console.log("test5\-\> ",data[0][5].value == vals2[4])
//END TEST 

This is the log from my console for m reference:

    dfg
    [[Object { key="Product_Description",  value="$100.83 Business Select Plan excl GST"}, Object { key=">20MB/30",  value=0.37336024217961655}, Object { key=">200MB/30",  value=0.3113017154389506}, 3 more...], [Object { key="Product_Description",  value="$119.95 Business Share Everything Plan"}, Object { key=">20MB/30",  value=66}, Object { key=">200MB/30",  value=57}, 3 more...]]
    function pp(s) {return JSON.stringify(s);}
    undefined
    pp(dfg)
    "[[{"key":"Product_Description","value":"$100.83 Business Select Plan excl GST"},{"key":">20MB/30","value":0.37336024217961655},{"key":">200MB/30","value":0.3113017154389506},{"key":">2048MB/30","value":0.17583249243188698},{"key":">5120MB/30","value":0.09561049445005046},{"key":">10240MB/30","value":0.04389505549949546}],[{"key":"Product_Description","value":"$119.95 Business Share Everything Plan"},{"key":">20MB/30","value":66},{"key":">200MB/30","value":57},{"key":">2048MB/30","value":30},{"key":">5120MB/30","value":14},{"key":">10240MB/30","value":6}]]"