If there is an uncertainty in the order of the fields then I would suggest you to use Hamcrest Matchers

You have not posted the responses so I can only give you examples

body(containsString("Hello World"));

or you could also try something like the below

body("find { it.userId == '123' }.subject", containsInAnyOrder("MATHS", "SCIENCE"))

Use RestAssured's JsonPath to parse the json file into a Map and then compare it with Hamcrest Matchers. This way the order etc didn't matter.

import static org.hamcrest.Matchers.equalTo;
import io.restassured.path.json.JsonPath;

...

JsonPath expectedJson = new JsonPath(new File("/path/to/expected.json"));

given()
    ...
    .then()
    .body("", equalTo(expectedJson.getMap("")));

I have been using JsonUnit and it really helps

String json1 = "{\r\n" + "  \"a\": 1,\r\n" + "  \"b\": 2,\r\n" + "  \"c\": 3,\r\n"
            + " \"date\": \"30-07-2020\"\r\n" + "}";

String json2 = "{\r\n" + "  \"a\": 1,\r\n" + "  \"b\": 2,\r\n" + "  \"c\": 3,\r\n"
            + " \"date\": \"31-07-2020\"\r\n" + "}";

assertThatJson(json1).whenIgnoringPaths("date").isEqualTo(json2);

Static Import :

import static net.javacrumbs.jsonunit.assertj.JsonAssertions.assertThatJson;

Dependency :

    <dependency>
        <groupId>net.javacrumbs.json-unit</groupId>
        <artifactId>json-unit-assertj</artifactId>
        <version>2.18.1</version>
        <scope>test</scope>
    </dependency>

You will have to add json.org or Jackson 1.x or Jackson 2.x or Johnzon or Gson to the classpath as well

I use Jackson

You can use any of the following methods

JsonPath :

String fileContent = FileUtils.getFileContent("test.json");

    JsonPath expectedJson = new JsonPath(fileContent);
    given().when().get("/testurl").then().body("", equalTo(expectedJson.getList("")));

Jackson :

String fileContent = FileUtils.getFileContent("test.json");
String def = given().when().get("/testurl").then().extract().asString();

    ObjectMapper mapper = new ObjectMapper();
    JsonNode expected = mapper.readTree(fileContent);
    JsonNode actual = mapper.readTree(def);
    Assert.assertEquals(actual,expected);

GSON :

String fileContent = FileUtils.getFileContent("test.json");
String def = given().when().get("/testurl").then().extract().asString();

    JsonParser parser = new JsonParser();
    JsonElement expected = parser.parse(fileContent);
    JsonElement actual = parser.parse(def);
    Assert.assertEquals(actual,expected);