created mapOffer test

src/test/java/de/rwu/easydrop/service/mapping/OfferMapperTest.java

@@ -1,5 +1,63 @@
 package de.rwu.easydrop.service.mapping;
 
-public class OfferMapperTest {
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.lang.reflect.Constructor;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Modifier;
+
+import org.junit.jupiter.api.Test;
+
+import de.rwu.easydrop.api.dto.OfferDTO;
+import de.rwu.easydrop.model.Offer;
+import de.rwu.easydrop.model.Product;
+import de.rwu.easydrop.model.Webshop;
+
+class OfferMapperTest {
+
+    @Test
+    void testConstructorIsPrivate()
+            throws NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {
+        // Check for private constructor
+        Constructor<OfferMapper> constructor = OfferMapper.class.getDeclaredConstructor();
+        assertTrue(Modifier.isPrivate(constructor.getModifiers()));
+
+        // Make sure exception is thrown when instantiating
+        constructor.setAccessible(true);
+        assertThrows(InvocationTargetException.class, () -> {
+            constructor.newInstance();
+        });
+    
+    }
+
+
+    @Test
+    void mapOfferToDTO() {
+        // Arrange
+        Product product = new Product();
+        product.setProductId("12345");
+        product.setDataOrigin(Webshop.AMAZON);
+        product.setAvailable(true);
+        product.setCurrentPrice(9.99);
+        product.setDeliveryPrice(2.50);
+        product.setMerchant("Seller1");
+
+        Offer offer = new Offer();
+        offer.setOfferId("68735");
+        offer.setLastUpdate("2020-07-07");
+        offer.setSourceProduct(product);
+        offer.setTargetProduct(product);
+
+        // Act
+        OfferDTO dto = OfferMapper.mapOfferToDTO(offer);
+
+        // Assert
+        assertEquals("68735", dto.getOfferId());
+        assertEquals("2020-07-07", dto.getLastUpdate());
+
+    }
+
 
 }

src/test/java/de/rwu/easydrop/service/validation/OfferValidatorTest.java

@@ -13,7 +13,7 @@ import de.rwu.easydrop.exception.InvalidOfferException;
 import de.rwu.easydrop.model.Offer;
 
 
-public class OfferValidatorTest {
+class OfferValidatorTest {
 
     @Test
     void validate_Offer_ValidProduct_NoExceptionThrown() {

src/test/java/de/rwu/easydrop/service/writer/OfferWriterTest.java

@@ -16,7 +16,7 @@ import de.rwu.easydrop.model.Offer;
 import de.rwu.easydrop.model.Product;
 import de.rwu.easydrop.model.Webshop;
 
-public class OfferWriterTest {
+class OfferWriterTest {
     
     @Mock
     private OfferDTO offerDTO;