#39 Added some unit tests

src/test/java/de/rwu/easydrop/util/FormattingUtilTest.java

@@ -0,0 +1,58 @@
+package de.rwu.easydrop.util;
+
+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.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class FormattingUtilTest {
+
+    @Test
+    public void testConstructorIsPrivate()
+            throws NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {
+        // Check for private constructor
+        Constructor<FormattingUtil> constructor = FormattingUtil.class.getDeclaredConstructor();
+        assertTrue(Modifier.isPrivate(constructor.getModifiers()));
+
+        // Make sure exception is thrown when instantiating
+        constructor.setAccessible(true);
+        assertThrows(InvocationTargetException.class, () -> {
+            constructor.newInstance();
+        });
+    }
+
+    @Test
+    public void testFormatEuro_positiveAmount() {
+        double amount = 1234.56;
+        String expectedFormattedAmount = "1.234,56 €";
+
+        String formattedAmount = FormattingUtil.formatEuro(amount);
+
+        Assertions.assertEquals(expectedFormattedAmount, formattedAmount);
+    }
+
+    @Test
+    public void testFormatEuro_zeroAmount() {
+        double amount = 0.0;
+        String expectedFormattedAmount = "0,00 €";
+
+        String formattedAmount = FormattingUtil.formatEuro(amount);
+
+        Assertions.assertEquals(expectedFormattedAmount, formattedAmount);
+    }
+
+    @Test
+    public void testFormatEuro_negativeAmount() {
+        double amount = -789.12;
+        String expectedFormattedAmount = "-789,12 €";
+
+        String formattedAmount = FormattingUtil.formatEuro(amount);
+
+        Assertions.assertEquals(expectedFormattedAmount, formattedAmount);
+    }
+}