// last element of inAndExpected is expected result
svoid mapLike testFunctionValue(O function, O... inAndExpected) {
  O expected = last(inAndExpected);
  O[] in = dropLast(inAndExpected);
  assertEqualsVerbose(renderFunctionCall(str(function), in), expected, mainFunctionToIF1Opt(function).get(in);
}