API Testing & Documenting Tools or Frameworks

I'm a Java Spring developer who (unfortunately) currently working on a Python Django project. As you may know, Spring REST Docs is a library that allows documenting API within integration (API) tests. Here is a sample API testing code using spring integration testing tools and spring rest docs:

this.mockMvc.perform(get("/user/5").accept(MediaType.APPLICATION_JSON))
        .andExpect(status().isOk())
        .andDo(document("index",
                responseFields( 
                        fieldWithPath("contact.email")
                                .description("The user's email address"), 
                fieldWithPath("contact.name").description("The user's name")))); 

As you may see, the big benefit of using Spring REST Docs is combining API tests with the API documentation. In this manner, developers will not forget to write/update an endpoint's documentation and, of course, it prevents duplicate code.

There are plenty of awesome API testing tools as well as hundreds of awesome API documentation tools. But I could not find any tool that combines API testing with API documenting, except a few commercial tools like Postman which has their own limitations. Is there any open-source (language-agnostic or language-specific) tool similar to Spring REST Docs?