`originalPositionFor` returns object with hidden properties

[Mingun]

I try to write a test for my source map generator and faced with a problem.
I use Jest as a testing library and a chai as a matcher:

it("my test", () => {
  const generated = { line: ..., column: ... };
  const original  = { line: ..., column: ..., source: ..., name: ... };
  const map = ...;
  
  return SourceMapConsumer.fromSourceMap(map).then(consumer => {
    chai.expect(consumer.originalPositionFor(generated)).to.be.equal(original);
  });
}

This test fails with a message:

● Peggy API › generate › generates source map › global initializer

  assert.deepStrictEqual(received, expected)

  Expected value to deeply and strictly equal to:
    {"column": 10, "line": 2, "name": "$top_level_initializer", "source": "-"}
  Received:
    {"column": 10, "line": 2, "name": "$top_level_initializer", "source": "-"}

  Message:
    expected { Object (source, line, ...) } to equal { Object (line, column, ...) }

  Difference:

  Compared values have no visual difference.

    240 |
    241 |         return SourceMapConsumer.fromSourceMap(map).then(consumer => {
  > 242 |           expect(consumer.originalPositionFor(generated)).to.be.equal(original);
        |                                                                 ^
    243 |         });
    244 |       }
    245 |

    at test/api/pegjs-api.spec.js:242:65

The jestjs/jest#5998 explains that this can happened because of additional properties in the one object. I'm absolutely sure that original is just a POD JSON object, so the problem in the originalPositionFor result. This creates difficults in testing

[Mingun]

Nevermind. It's my fault. Chai's equal performs strict assertions. The correct assertion in my case would be with deep:

    chai.expect(consumer.originalPositionFor(generated)).to.be.deep.equal(original);