MockMvc: verify JSON response structure with jsonPath

Tests that assert the full serialized JSON string are brittle — whitespace differences, field ordering, and unrelated additions break the test. A better approach asserts specific fields and structures.

Use MockMvc with jsonPath assertions:

mockMvc.perform(post("/orders")
    .contentType(MediaType.APPLICATION_JSON)
    .content(objectMapper.writeValueAsString(request)))
    .andExpect(status().isCreated())
    .andExpect(header().string("Location", matchesPattern("/orders/\\d+")))
    .andExpect(jsonPath("$.id").isNumber())
    .andExpect(jsonPath("$.status").value("PENDING"))
    .andExpect(jsonPath("$.items").isArray())
    .andExpect(jsonPath("$.items", hasSize(2)))
    .andExpect(jsonPath("$.items[0].productId").value("SKU-001"))
    .andDo(print()); // print request/response for debugging

For complex assertions, deserialize the response:

String body = result.andReturn().getResponse().getContentAsString();
OrderResponse order = objectMapper.readValue(body, OrderResponse.class);
assertThat(order.total()).isEqualByComparingTo("49.99");

JSONPath expressions navigate the JSON tree without caring about unrelated fields. Tests remain valid when new fields are added to the response, and the assertion intent is clear.