Why I cannot validate the response's value is {}?

@tester20183450 You can read this SO thread to understand it better

Using the recommended format of writing tests using pm.test, you can check if the object is empty.

pm.test('The args should be empty', function () {
  pm.expect(jsonData.args).to.eql({});
});

In addition to what @sivcan mentioned, you should also look into using the new Postman testing format (see the Snippets for a quick start).

The following assertion will work using eql :

pm.expect({a: 1}).to.eql({a: 1})

@tester20183450
If you want to confirm an object was returned, you could do this with the following:

pm.test("Expect 'args' to be an object", function() {
    pm.expect(jsonData.args).to.be.an("object");
});

I can see you’re using the “old” syntax to write tests, so I’m guessing this could be done with the following - I haven’t used this syntax in over a year so it could be wrong:

tests["Expect 'args' to be an object"] = typeof jsonData.args === "object";