{
  "cases":[
    {
        "case_no":1,
        "case_input":"Test 1",
        "case_output":"Test 1"
    },
    {
        "case_no":2,
        "case_input":"Test 2",
        "case_output":"Test 2"
    }
        ]
}

$testcases = "["Test 1", "Test 2"]";

var testcases = [];
                  for(var j in data.cases ){
                    testcases[j]= data.cases[j].case_input;
                  }
                  testcase = JSON.stringify(testcases);