truffle testing enum

Question

I am trying to test an enum value from a test. This is simplified version of the contract:

pragma solidity >=0.5.0 <0.7.0;

contract Foo {

  enum State {
    StateA,
    StateB
  }

  State internal state;

  function getState()
    public view
    returns (State)
  {
    return state;
  }
}

Now running the test just like this:

contract("Foo", async accounts => {
  it("requires a project to create", async () => {
    let instance = await Foo.new()
    console.log(await instance.getState())
  })
})

I am getting output like this

BN { negative: 0, words: [ 1, <1 empty item> ], length: 1, red: null }

I've read that enums are still not supported from the ABI but shouldn't this then just return the index? What is BN? negative? red?

Answer 1

Enums are returned as uint256.

BN means big number, it is a javascript object that wraps an arbitrary precision integer, it is used to wrap uint256.

When it prints some values like words, red, negative, etc. it is javascript that is trying to show some internal data that is not useful unless you develop BN package.

You get more info if you convert to string before printing to console

console.log((await instance.getState()).toString())