test(idempotency): add keyPrefix test for decorator

packages/idempotency/tests/unit/idempotencyDecorator.test.ts

@@ -1,9 +1,10 @@
 import type { LambdaInterface } from '@aws-lambda-powertools/commons/types';
 import context from '@aws-lambda-powertools/testing-utils/context';
 import type { Context } from 'aws-lambda';
-import { describe, expect, it } from 'vitest';
-import { idempotent } from '../../src/index.js';
+import { describe, expect, it, vi } from 'vitest';
+import { idempotent, IdempotencyConfig } from '../../src/index.js';
 import { PersistenceLayerTestClass } from '../helpers/idempotencyUtils.js';
+import { BasePersistenceLayer } from '../../src/persistence/BasePersistenceLayer.js';
 
 describe('Given a class with a function to decorate', () => {
   it('maintains the scope of the decorated function', async () => {
@@ -35,4 +36,42 @@ describe('Given a class with a function to decorate', () => {
     // Assess
     expect(result).toBe('private foo');
   });
+
+  it('configure persistenceStore idempotency key with custom keyPrefix', async () => {
+    // Prepare
+    const configureSpy = vi.spyOn(BasePersistenceLayer.prototype, 'configure');
+    const idempotencyConfig = new IdempotencyConfig({});
+
+    class TestClass implements LambdaInterface {
+      @idempotent({
+        persistenceStore: new PersistenceLayerTestClass(),
+        config: idempotencyConfig,
+        keyPrefix: 'my-custom-prefix',
+      })
+      public async handler(
+        _event: unknown,
+        _context: Context
+      ): Promise<boolean> {
+        return true;
+      }
+    }
+
+    const handlerClass = new TestClass();
+    const handler = handlerClass.handler.bind(handlerClass);
+
+    // Act
+    const result = await handler({}, context);
+
+
+    // Assert
+    expect(result).toBeTruthy();
+
+    expect(configureSpy).toHaveBeenCalled();
+    const configureCallArgs = configureSpy.mock.calls[0][0]; // Extract first call's arguments
+    expect(configureCallArgs.config).toBe(idempotencyConfig);
+    expect(configureCallArgs.keyPrefix).toBe('my-custom-prefix');
+
+    // Restore the spy
+    configureSpy.mockRestore();
+  });
 });