Add integration test for InventoryInitializer

src/test/java/catering/inventory/InventoryInitializerIntegrationTests.java

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+// SPDX-License-Identifier: AGPL-3.0-or-later
+// SPDX-FileCopyrightText: 2024 swt23w23
+package catering.inventory;
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.Set;
+import java.util.stream.Collectors;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.salespointframework.inventory.UniqueInventory;
+import org.salespointframework.inventory.UniqueInventoryItem;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+
+import catering.catalog.CateringCatalog;
+
+@SpringBootTest
+class InventoryInitializerIntegrationTests {
+	@Autowired
+	UniqueInventory<UniqueInventoryItem> inventory;
+	@Autowired
+	CateringCatalog cateringCatalog;
+
+	InventoryInitializer inventoryInitializer;
+
+	@BeforeEach
+	void init() {
+		inventoryInitializer = new InventoryInitializer(inventory, cateringCatalog);
+	}
+
+	/**
+	 * Test if the inventory items are only created once.
+	 *
+	 * After the first startup,
+	 * the catalog entries will only be changed through the inventory interfaces,
+	 * which automatically keep the catalog in sync.
+	 */
+	@Test
+	void onlyRunOnce() {
+		// the first run is already done
+		Set<UniqueInventoryItem> before = inventory.findAll().stream().collect(Collectors.toSet());
+		inventoryInitializer.initialize();
+		Set<UniqueInventoryItem> after = inventory.findAll().stream().collect(Collectors.toSet());
+
+		assertThat(before).hasSameElementsAs(after);
+	}
+}