Testing with Assert (fails) vs Testing with Expect (passes)

[dimitar-dermendzhiev]

I have the following function in my test file

const tokens = (amount) => {
  return ethers.utils.parseUnits(amount, "ether");
};

and in my describe function I have the total supply set like this

const totalSupply = tokens("1000000");

in my it function I have the following assert statement which fails

assert.equal(await token.totalSupply(), totalSupply);

if I use expect instead of assert the test passes

 expect(await token.totalSupply()).to.equal(totalSupply);

I checked the type of both objects and it says they are both of type object BigNumber and they both have the same value which makes me confused why the assert fails and the expect passes.

The assert statement passes if do it like this

assert.equal(await token.totalSupply(), totalSupply.toString());

But then it comes my question. Why I have to use the toString() method when using assert and not using it when doing expect?