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libs/api/tracker/domain/src/lib/testing.ts

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+import {
+  SerializableEvent,
+  VersionedAggregateRoot,
+} from '@task-stream/api/shared/domain';
+
+/**
+ * Round-trips uncommitted events like the event store does (JSON + class
+ * prototype) and rebuilds a fresh aggregate from them.
+ */
+export function replay<T extends VersionedAggregateRoot>(
+  aggregate: T,
+  AggregateCls: new (id: string) => T,
+  previous: SerializableEvent[] = [],
+): { rebuilt: T; history: SerializableEvent[] } {
+  const history = [
+    ...previous,
+    ...aggregate.getUncommittedEvents().map((event, index) => ({
+      streamId: aggregate.id,
+      type: event.constructor.name,
+      position: previous.length + index + 1,
+      data: Object.assign(
+        Object.create(Object.getPrototypeOf(event)),
+        JSON.parse(JSON.stringify(event)),
+      ),
+    })),
+  ];
+  const rebuilt = new AggregateCls(aggregate.id);
+  rebuilt.loadFromHistory(history);
+  return { rebuilt, history };
+}