assertSame(request, result); // Fluent API
        assertNull(request.body()); // body() returns String body, not stream
    }

    @Test
    public void testBodyStringAfterStreamThrowsException() {
        CurlRequest request = new CurlRequest(Method.POST, "https://example.com");
        InputStream stream = new ByteArrayInputStream("test data".getBytes());
        request.body(stream);