Added and rewrote tests

src/test/java/de/rwu/easydrop/model/ProductPairTest.java

@@ -0,0 +1,25 @@
+package de.rwu.easydrop.model;
+
+import static org.junit.jupiter.api.Assertions.assertSame;
+
+import org.junit.jupiter.api.Test;
+
+class ProductPairTest {
+
+    @Test
+    void constructor_TwoProducts_ProductsInitializedCorrectly() {
+        // Arrange
+        Product product1 = new Product();
+        product1.setProductId("123");
+
+        Product product2 = new Product();
+        product2.setProductId("234");
+
+        // Act
+        ProductPair pair = new ProductPair(product1, product2);
+
+        // Assert
+        assertSame(product1, pair.getProduct1());
+        assertSame(product2, pair.getProduct2());
+    }
+}

src/test/java/de/rwu/easydrop/model/WebshopTest.java

@@ -0,0 +1,23 @@
+package de.rwu.easydrop.model;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import org.junit.jupiter.api.Test;
+
+class WebshopTest {
+
+    @Test
+    void testFromString_returnsIntendedConstant() {
+        Webshop testShop = Webshop.fromString("Amazon");
+
+        assertEquals(Webshop.AMAZON, testShop);
+    }
+
+    @Test
+    void testFromString_invalidShop() {
+        assertThrows(IllegalArgumentException.class, () -> {
+            Webshop.fromString("thisdoesnotexist");
+        });
+    }
+}