For expl.

mapping(uint => Test) tests;

struct Test {
    uint id;
    mapping(address => uint) votes;
function newTest() public {
    test[0] = Test(0, <EMPTY_MAPPING>)

You can rewrite your code like this:

tests[0] = Test({
  id: 0

Solidity will make votes an empty mapping by default. Btw, there's also a typo in your code: should be tests[0] instead of test[0].

  • Wrote that in Stackexchange instead of int he IDE. Thanks Paul that'll do it, I could not find the question you asked earlier.
    – jasper
    Nov 21 '18 at 13:19

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