The urine test

Two children, Johnny and Alex were sitting outside a clinic.  Alex was crying very loudly.  Johnny: Why are you crying?  Alex: I came here for a blood test.  Johnny: So? Are you afraid?  Alex: No. For the blood test, they cut my finger. After hearing this Johnny started weeping making Alex feel surprised as well as curious and Alex asked: Why are you crying now? Johnny: I came for a urine test!