async def test_no_builtin_headers(self,
                                      pytestconfig,
                                      nghttpd,
                                      curl_binary,
                                      env_vars,
                                      ld_preload):
        """
        Ensure the built-in headers of libcurl-impersonate are not added when
        the CURL_IMPERSONATE_HEADERS environment variable is set to "no".
        """
        curl_binary = os.path.join(
            pytestconfig.getoption("install_dir"), "bin", curl_binary
        )

        if not sys.platform.startswith("linux"):
            pytest.skip()

        self._set_ld_preload(env_vars, os.path.join(
            pytestconfig.getoption("install_dir"), "lib", ld_preload
        ))

        # Use some custom headers with a specific order.
        # We will test that the headers are sent in the exact given order, as
        # it is important for users to be able to control the exact headers
        # content and order.
        headers = [
            "X-Hello: World",
            "Accept: application/json",
            "X-Goodbye: World",
            "Accept-Encoding: deflate, gzip, br"
            "X-Foo: Bar",
            "User-Agent: curl-impersonate"
        ]
        header_args = list(itertools.chain(*[
            ["-H", header]
            for header in  headers
        ]))

        ret = self._run_curl(curl_binary,
                             env_vars=env_vars,
                             extra_args=["-k"] + header_args,
                             urls=["https://localhost:8443"])
        assert ret == 0

        output = await self._read_proc_output(nghttpd, timeout=2)

        assert len(output) > 0
        _, output_headers = self._parse_nghttpd2_output(output)
        for i, header in enumerate(output_headers):
            assert header.lower() == headers[i].lower()

        Ensure the built-in headers of libcurl-impersonate are not added when
        the CURL_IMPERSONATE_HEADERS environment variable is set to "no".
        
tests/test_impersonate.py