import javascript

class Assertion extends DataFlow::CallNode {
  Assertion() {
    getCalleeName() = "checkJSON"
  }

  string getMessage() {
    if not any(JsonParserCall call).getOutput().flowsTo(getArgument(0)) then
      result = "Should be JSON parser"
    else
      result = "OK"
  }
}

from Assertion assertion
select assertion, assertion.getMessage()