[OPIK-8181] [BE] refactor: centralise dataset item test assertions in DatasetItemAssertions

.agents/skills/opik-backend/testing.md

@@ -295,19 +295,38 @@ assertThat(stored).hasSize(2);
 assertThat(version.itemsTotal()).isEqualTo(stored.size());
 
 // ✅ GOOD - names the rows that must survive, so a wrong-winner bug fails
-assertThat(stored)
-    .usingRecursiveFieldByFieldElementComparatorIgnoringFields(IGNORED_FIELDS_DATA_ITEM)
-    .containsExactlyInAnyOrder(winningDuplicate, distinctItem);
+assertDatasetItemsInAnyOrder(stored, winningDuplicate, distinctItem);
 assertThat(version.itemsTotal()).isEqualTo(stored.size());
 ```
 
 Asserting a derived counter against `stored.size()` is good — it ties the counter to reality
 rather than to a literal — but it is only as strong as the assertion on `stored` itself. Pin the
 contents first, then tie the counter to them.
 
-Reuse the shared ignore-field constants (`IGNORED_FIELDS_DATA_ITEM` and friends) rather than
-declaring a local list: they already encode which server-generated fields are not part of the
-contract, and a local copy silently drifts from them.
+Reach for the assertion helper before the constant. Where a helper class or method already covers
+the entity, call it — reusing only its ignore-field constant still leaves the comparator chain
+re-derived at each call site, which is what drifts. The helpers live under
+`api/resources/utils/`: `TraceAssertions`, `SpanAssertions`, `DatasetItemAssertions`,
+`AlertAssertions`, `PromptTestAssertions` and `ExperimentTestAssertions`.
+
+```java
+// ❌ BAD - comparator chain re-derived; the next field to ignore has to be found here too
+assertThat(actualItems)
+    .usingRecursiveFieldByFieldElementComparatorIgnoringFields(IGNORED_FIELDS_DATA_ITEM)
+    .containsExactlyElementsOf(expectedItems);
+
+// ✅ GOOD - the helper owns both the ignore list and the comparison
+assertDatasetItemsInOrder(actualItems, expectedItems);
+```
+
+Each helper owns its ignore-field constant, so the constant has exactly one declaration. Never
+declare a local copy and never import one from another test class: a second copy drifts silently,
+and the resulting failure reads like a product bug rather than a stale ignore list. When a call
+site needs one extra field ignored, derive it from the shared constant (see
+`DatasetItemAssertions.ignoredFieldsPlus`) rather than rebuilding the list.
+
+If no helper exists for the entity yet and more than one test class needs the assertion, add one
+under `api/resources/utils/` rather than hoisting a constant into a test class.
 
 These `containsExactly*` variants compare elements with the element type's own `equals`, which is
 what you want for exact-valued models. When the elements carry `BigDecimal` or `double`, the same

apps/opik-backend/src/test/java/com/comet/opik/api/resources/utils/datasets/DatasetItemAssertions.java

@@ -0,0 +1,55 @@
+package com.comet.opik.api.resources.utils.datasets;
+
+import com.comet.opik.api.DatasetItem;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Stream;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class DatasetItemAssertions {
+
+    public static final String[] IGNORED_FIELDS_DATA_ITEM = {"createdAt", "lastUpdatedAt", "experimentItems",
+            "createdBy", "lastUpdatedBy", "datasetId", "tags", "datasetItemId", "runSummariesByExperiment"};
+
+    /**
+     * Extends {@link #IGNORED_FIELDS_DATA_ITEM} for call sites that ignore an extra field here and then assert it
+     * separately, because it needs different semantics than plain recursive equality.
+     */
+    public static String[] ignoredFieldsPlus(String... extraFields) {
+        return Stream.concat(Arrays.stream(IGNORED_FIELDS_DATA_ITEM), Arrays.stream(extraFields))
+                .toArray(String[]::new);
+    }
+
+    public static void assertDatasetItem(DatasetItem actual, DatasetItem expected) {
+        assertThat(actual)
+                .usingRecursiveComparison()
+                .ignoringFields(IGNORED_FIELDS_DATA_ITEM)
+                .isEqualTo(expected);
+    }
+
+    public static void assertDatasetItems(List<DatasetItem> actual, List<DatasetItem> expected) {
+        assertThat(actual)
+                .usingRecursiveFieldByFieldElementComparatorIgnoringFields(IGNORED_FIELDS_DATA_ITEM)
+                .isEqualTo(expected);
+    }
+
+    public static void assertDatasetItemsInOrder(List<DatasetItem> actual, List<DatasetItem> expected) {
+        assertThat(actual)
+                .usingRecursiveFieldByFieldElementComparatorIgnoringFields(IGNORED_FIELDS_DATA_ITEM)
+                .containsExactlyElementsOf(expected);
+    }
+
+    public static void assertDatasetItemsInAnyOrder(List<DatasetItem> actual, DatasetItem... expected) {
+        assertThat(actual)
+                .usingRecursiveFieldByFieldElementComparatorIgnoringFields(IGNORED_FIELDS_DATA_ITEM)
+                .containsExactlyInAnyOrder(expected);
+    }
+
+    public static void assertDatasetItemsContain(List<DatasetItem> actual, List<DatasetItem> expected) {
+        assertThat(actual)
+                .usingRecursiveFieldByFieldElementComparatorIgnoringFields(IGNORED_FIELDS_DATA_ITEM)
+                .containsAll(expected);
+    }
+}

apps/opik-backend/src/test/java/com/comet/opik/api/resources/v1/priv/DatasetVersionResourceTest.java

@@ -104,7 +104,11 @@
 
 import static com.comet.opik.api.resources.utils.ClickHouseContainerUtils.DATABASE_NAME;
 import static com.comet.opik.api.resources.utils.WireMockUtils.WireMockRuntime;
-import static com.comet.opik.api.resources.v1.priv.DatasetsResourceTest.IGNORED_FIELDS_DATA_ITEM;
+import static com.comet.opik.api.resources.utils.datasets.DatasetItemAssertions.assertDatasetItem;
+import static com.comet.opik.api.resources.utils.datasets.DatasetItemAssertions.assertDatasetItems;
+import static com.comet.opik.api.resources.utils.datasets.DatasetItemAssertions.assertDatasetItemsContain;
+import static com.comet.opik.api.resources.utils.datasets.DatasetItemAssertions.assertDatasetItemsInAnyOrder;
+import static com.comet.opik.api.resources.utils.datasets.DatasetItemAssertions.assertDatasetItemsInOrder;
 import static com.comet.opik.infrastructure.db.TransactionTemplateAsync.READ_ONLY;
 import static com.comet.opik.infrastructure.db.TransactionTemplateAsync.WRITE;
 import static org.assertj.core.api.Assertions.assertThat;
@@ -1078,9 +1082,7 @@ void applyChanges__whenCombinedAddEditDelete__thenCreateNewVersion() {
             var v1ItemsAfter = datasetResourceClient.getDatasetItems(
                     datasetId, 1, 10, "v1", API_KEY, TEST_WORKSPACE).content();
             assertThat(v1ItemsAfter).hasSize(3);
-            assertThat(v1ItemsAfter)
-                    .usingRecursiveFieldByFieldElementComparatorIgnoringFields(IGNORED_FIELDS_DATA_ITEM)
-                    .isEqualTo(v1Items);
+            assertDatasetItems(v1ItemsAfter, v1Items);
         }
 
         @Test
@@ -1353,10 +1355,8 @@ void applyChanges__whenBaseVersionItemsTotalIsStale__thenUnchangedItemsArePreser
             assertThat(v2Items).hasSize(6);
 
             // Every v1 item must appear in v2 with the same fields. id changes per version, so
-            // we ignore it via IGNORED_FIELDS_DATA_ITEM and compare the rest of the entity.
-            assertThat(v2Items)
-                    .usingRecursiveFieldByFieldElementComparatorIgnoringFields(IGNORED_FIELDS_DATA_ITEM)
-                    .containsAll(v1Items);
+            // the helper ignores it and compares the rest of the entity.
+            assertDatasetItemsContain(v2Items, v1Items);
         }
     }
 
@@ -1561,9 +1561,7 @@ void deleteItems__whenBaseVersionItemsTotalIsStale__thenUnchangedItemsArePreserv
             assertThat(v2Items.stream().map(DatasetItem::datasetItemId))
                     .doesNotContain(itemToDelete.datasetItemId());
 
-            assertThat(v2Items)
-                    .usingRecursiveFieldByFieldElementComparatorIgnoringFields(IGNORED_FIELDS_DATA_ITEM)
-                    .containsAll(expectedSurvivors);
+            assertDatasetItemsContain(v2Items, expectedSurvivors);
         }
 
         @Test
@@ -3613,18 +3611,14 @@ void sortByJsonKeyThroughPushTopLimit(String namespace, String jsonKey, Directio
                     datasetId, List.of(experimentId), null, null, sorting, API_KEY, TEST_WORKSPACE);
 
             // Compare the whole DatasetItem objects, in order - not just their ids.
-            assertThat(sorted.content())
-                    .usingRecursiveFieldByFieldElementComparatorIgnoringFields(IGNORED_FIELDS_DATA_ITEM)
-                    .containsExactlyElementsOf(expected);
+            assertDatasetItemsInOrder(sorted.content(), expected);
 
             // Page boundary: with size=2, page 2 returns only the trailing item in sort order, exercising the
             // push-top-limit OFFSET :top_offset + outer LIMIT path; total stays at the full matching count.
             var pageTwo = datasetResourceClient.getDatasetItemsWithExperimentItems(
                     datasetId, List.of(experimentId), null, null, sorting, 2, 2, API_KEY, TEST_WORKSPACE);
             assertThat(pageTwo.total()).isEqualTo(count);
-            assertThat(pageTwo.content())
-                    .usingRecursiveFieldByFieldElementComparatorIgnoringFields(IGNORED_FIELDS_DATA_ITEM)
-                    .containsExactly(expected.get(count - 1));
+            assertDatasetItemsInOrder(pageTwo.content(), List.of(expected.get(count - 1)));
         }
 
         @Test
@@ -3842,12 +3836,9 @@ void putItems__whenCreatingBatchRepeatsStableId__thenCountedOnce() {
             // counter that agrees with it.
             assertThat(stored).extracting(DatasetItem::id)
                     .containsExactlyInAnyOrder(duplicatedId, distinctId);
-            assertThat(stored)
-                    .filteredOn(item -> distinctId.equals(item.id()))
-                    .singleElement()
-                    .usingRecursiveComparison()
-                    .ignoringFields(IGNORED_FIELDS_DATA_ITEM)
-                    .isEqualTo(distinctItem);
+            var storedDistinctItems = stored.stream().filter(item -> distinctId.equals(item.id())).toList();
+            assertThat(storedDistinctItems).hasSize(1);
+            assertDatasetItem(storedDistinctItems.getFirst(), distinctItem);
 
             // items_total must agree with what is actually stored.
             assertThat(version.itemsTotal()).isEqualTo(stored.size());
@@ -3903,9 +3894,7 @@ void putItems__whenDuplicateStableIdSpansBatchesInGroup__thenCountedOnce() {
             var stored = datasetResourceClient.getDatasetItems(
                     datasetId, 1, 100, version.versionHash(), API_KEY, TEST_WORKSPACE).content();
 
-            assertThat(stored)
-                    .usingRecursiveFieldByFieldElementComparatorIgnoringFields(IGNORED_FIELDS_DATA_ITEM)
-                    .containsExactlyInAnyOrder(updatedShared, otherItem);
+            assertDatasetItemsInAnyOrder(stored, updatedShared, otherItem);
             assertThat(version.itemsTotal()).isEqualTo(stored.size());
         }
 
@@ -4801,9 +4790,7 @@ void applyChanges__whenEvaluatorAndDescriptionContainJsonEscapeSequences__thenIt
                     .evaluators(newEvaluators)
                     .description(newDescription)
                     .build();
-            assertThat(v2Items)
-                    .usingRecursiveFieldByFieldElementComparatorIgnoringFields(IGNORED_FIELDS_DATA_ITEM)
-                    .containsExactly(expectedItem);
+            assertDatasetItemsInOrder(v2Items, List.of(expectedItem));
         }
 
         @Test
@@ -5372,10 +5359,7 @@ void createItems__whenDescription__thenFieldReturned() {
             var expectedItem = items.getFirst().toBuilder()
                     .id(returnedItem.id())
                     .build();
-            assertThat(returnedItem)
-                    .usingRecursiveComparison()
-                    .ignoringFields(IGNORED_FIELDS_DATA_ITEM)
-                    .isEqualTo(expectedItem);
+            assertDatasetItem(returnedItem, expectedItem);
         }
 
         @Test

apps/opik-backend/src/test/java/com/comet/opik/api/resources/v1/priv/DatasetsResourceTest.java

@@ -144,7 +144,6 @@
 import java.time.Instant;
 import java.time.temporal.ChronoUnit;
 import java.util.ArrayList;
-import java.util.Arrays;
 import java.util.Collection;
 import java.util.Comparator;
 import java.util.HashMap;
@@ -181,6 +180,9 @@
 import static com.comet.opik.api.resources.utils.TestUtils.getIdFromLocation;
 import static com.comet.opik.api.resources.utils.TestUtils.toURLEncodedQueryParam;
 import static com.comet.opik.api.resources.utils.WireMockUtils.WireMockRuntime;
+import static com.comet.opik.api.resources.utils.datasets.DatasetItemAssertions.assertDatasetItem;
+import static com.comet.opik.api.resources.utils.datasets.DatasetItemAssertions.assertDatasetItemsInOrder;
+import static com.comet.opik.api.resources.utils.datasets.DatasetItemAssertions.ignoredFieldsPlus;
 import static com.comet.opik.api.resources.v1.priv.OptimizationsResourceTest.OPTIMIZATION_IGNORED_FIELDS;
 import static com.comet.opik.infrastructure.auth.RequestContext.SESSION_COOKIE;
 import static com.comet.opik.infrastructure.auth.RequestContext.WORKSPACE_HEADER;
@@ -216,8 +218,6 @@ class DatasetsResourceTest {
 
     public static final String[] IGNORED_FIELDS_LIST = {"feedbackScores", "createdAt", "lastUpdatedAt", "createdBy",
             "lastUpdatedBy", "comments", "projectName", "traceMetadata"};
-    public static final String[] IGNORED_FIELDS_DATA_ITEM = {"createdAt", "lastUpdatedAt", "experimentItems",
-            "createdBy", "lastUpdatedBy", "datasetId", "tags", "datasetItemId", "runSummariesByExperiment"};
     public static final String[] DATASET_IGNORED_FIELDS = {"id", "createdAt", "lastUpdatedAt", "createdBy",
             "lastUpdatedBy", "projectName", "experimentCount", "mostRecentExperimentAt", "lastCreatedExperimentAt",
             "datasetItemsCount", "lastCreatedOptimizationAt", "mostRecentOptimizationAt", "optimizationCount",
@@ -4862,9 +4862,7 @@ private DatasetItem getItemAndAssert(DatasetItem expectedDatasetItem, String wor
         assertThat(actualResponse.getStatusInfo().getStatusCode()).isEqualTo(200);
 
         assertThat(actualEntity.id()).isEqualTo(expectedDatasetItem.id());
-        assertThat(actualEntity).usingRecursiveComparison()
-                .ignoringFields(IGNORED_FIELDS_DATA_ITEM)
-                .isEqualTo(expectedDatasetItem);
+        assertDatasetItem(actualEntity, expectedDatasetItem);
 
         assertThat(actualEntity.createdAt()).isInThePast();
         assertThat(actualEntity.lastUpdatedAt()).isInThePast();
@@ -6594,11 +6592,8 @@ private void assertDatasetItemPage(DatasetItemPage actualPage, List<DatasetItem>
 
     private void assertPage(List<DatasetItem> expectedItems, List<DatasetItem> actualItems) {
 
-        List<String> ignoredFields = new ArrayList<>(Arrays.asList(IGNORED_FIELDS_DATA_ITEM));
-        ignoredFields.add("data");
-
         assertThat(actualItems)
-                .usingRecursiveFieldByFieldElementComparatorIgnoringFields(ignoredFields.toArray(String[]::new))
+                .usingRecursiveFieldByFieldElementComparatorIgnoringFields(ignoredFieldsPlus("data"))
                 .isEqualTo(expectedItems);
 
         assertThat(actualItems).hasSize(expectedItems.size());
@@ -9068,9 +9063,7 @@ private void assertSortedByKey(UUID datasetId, String experimentIdsParam, String
 
             // Compare the whole DatasetItem objects, in order - not just their ids - so the assertion proves
             // the bound key actually drives the ordering. Volatile/derived fields are ignored per suite convention.
-            assertThat(actualItems)
-                    .usingRecursiveFieldByFieldElementComparatorIgnoringFields(IGNORED_FIELDS_DATA_ITEM)
-                    .containsExactlyElementsOf(expectedItems);
+            assertDatasetItemsInOrder(actualItems, expectedItems);
         }
 
         private List<DatasetItem> fetchDatasetItems(UUID datasetId, String experimentIdsParam, String sortField,

apps/opik-backend/src/test/java/com/comet/opik/domain/ExperimentAggregatesIntegrationTest.java

@@ -95,6 +95,7 @@
 import java.util.stream.Stream;
 
 import static com.comet.opik.api.resources.utils.ClickHouseContainerUtils.DATABASE_NAME;
+import static com.comet.opik.api.resources.utils.datasets.DatasetItemAssertions.assertDatasetItems;
 import static org.assertj.core.api.Assertions.assertThat;
 
 @TestInstance(TestInstance.Lifecycle.PER_CLASS)
@@ -127,9 +128,6 @@ class ExperimentAggregatesIntegrationTest {
     private final MySQLContainer MYSQL = MySQLContainerUtils.newMySQLContainer();
     private final RandomGenerator random = new Random();
 
-    public static final String[] IGNORED_FIELDS_DATA_ITEM = {"createdAt", "lastUpdatedAt", "experimentItems",
-            "createdBy", "lastUpdatedBy", "datasetId", "tags", "datasetItemId"};
-
     public static final String[] IGNORED_FIELDS_EXPERIMENT_ITEM = {"createdAt", "lastUpdatedAt", "createdBy",
             "lastUpdatedBy", "comments", "projectName", "executionPolicy"};
 
@@ -1506,9 +1504,7 @@ void getDatasetItemsWithExperimentItemsFromAggregates(
     void assertDatasetItemsWithExperimentItems(List<DatasetItem> expectedDatasetItem,
             List<DatasetItem> actualDatasetItems) {
 
-        assertThat(actualDatasetItems)
-                .usingRecursiveFieldByFieldElementComparatorIgnoringFields(IGNORED_FIELDS_DATA_ITEM)
-                .isEqualTo(expectedDatasetItem);
+        assertDatasetItems(actualDatasetItems, expectedDatasetItem);
 
         for (var i = 0; i < actualDatasetItems.size(); i++) {
             var actualExperiments = actualDatasetItems.get(i).experimentItems();