When this test fails nobody can tell what changed

Problem Description

OrderSnapshotIT compares the whole response body of GET /v1/orders/42 against a checked-in file. It fails most mornings, and when it does the CI log contains two four-kilobyte JSON blobs and the word expected. Working out what actually differs means copying both blobs into a diff tool.

The daily failures are all the same three fields - the order carries a created_at, a trace_id, and an etag that change on every deploy of the service, and one of them changes on every read. Nobody disputes those fields should be there; they just can't be pinned to a value.

The team's habit is now to re-run the test, and if it fails again, regenerate expected/order-42.json from the live response and commit it. That has twice swallowed a real change: once when status silently started coming back as "SHIPPED" instead of "shipped", and once when the items[].sku format changed and we shipped a client that couldn't parse it.

Output Specification

1. Rework OrderSnapshotIT so a failure names the field that changed rather than printing the whole document.
2. The three volatile fields must not be able to fail the build on their value, but their absence or a malformed value must still fail.
3. Keep coverage of every field the current comparison covers - list them in your answer so a reviewer can check nothing was dropped.
4. Remove or demote expected/order-42.json if it is no longer authoritative, and say what should happen the next time somebody's instinct is to regenerate it.

Out of scope: pom.xml is frozen - no new dependencies, no new plugins. Do not change the endpoint or add HTTP calls.

Input Files

Extract the following files before beginning.

=============== FILE: src/test/java/com/example/orders/OrderSnapshotIT.java =============== package com.example.orders;

import io.restassured.RestAssured; import io.restassured.http.ContentType; import org.junit.jupiter.api.BeforeAll; import org.junit.jupiter.api.DisplayName; import org.junit.jupiter.api.Test;

import java.nio.charset.StandardCharsets; import java.nio.file.Files; import java.nio.file.Path;

import static io.restassured.RestAssured.given; import static org.hamcrest.Matchers.equalTo;

class OrderSnapshotIT {

private static String expected;

@BeforeAll static void setup() throws Exception { RestAssured.baseURI = System.getProperty("api.baseURI", "http://localhost:8080"); expected = Files.readString( Path.of("src/test/resources/expected/order-42.json"), StandardCharsets.UTF_8).trim(); }

@Test @DisplayName("GET /v1/orders/42 matches the recorded snapshot") void orderMatchesSnapshot() { given(). auth().oauth2(System.getenv("API_TOKEN")). accept(ContentType.JSON). when(). get("/v1/orders/42"). then(). statusCode(200). body(equalTo(expected)); } }

=============== FILE: src/test/resources/expected/order-42.json =============== { "order_id": 42, "customer_id": "CUST-9", "status": "shipped", "currency": "EUR", "total_cents": 5100, "created_at": "2026-08-11T09:14:02Z", "trace_id": "f0b1c2d3-4e5f-4a6b-8c9d-0e1f2a3b4c5d", "etag": "W/"7c1f-19812ab"", "shipping": { "carrier": "DPD", "tracking_number": "DPD-8891023", "country": "DE" }, "items": [ { "sku": "AB12CD34", "quantity": 2, "unit_price_cents": 1800 }, { "sku": "EF56GH78", "quantity": 1, "unit_price_cents": 1500 } ] }