Added and rewrote tests

src/test/java/de/rwu/easydrop/exception/InvalidTransactionExceptionTest.java

@@ -0,0 +1,61 @@
+package de.rwu.easydrop.exception;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import org.junit.jupiter.api.Test;
+
+class InvalidTransactionExceptionTest {
+
+    @Test
+    void constructor_WithMessage_SetsMessage() {
+        // Arrange
+        String message = "Invalid Transaction data";
+
+        // Act
+        InvalidTransactionException exception = new InvalidTransactionException(message);
+
+        // Assert
+        assertEquals(message, exception.getMessage());
+    }
+
+    @Test
+    void constructor_WithMessageAndCause_SetsMessageAndCause() {
+        // Arrange
+        String message = "Invalid Transaction data";
+        Throwable cause = new IllegalArgumentException("Invalid argument");
+
+        // Act
+        InvalidTransactionException exception = new InvalidTransactionException(message, cause);
+
+        // Assert
+        assertEquals(message, exception.getMessage());
+        assertEquals(cause, exception.getCause());
+    }
+
+    @Test
+    void constructor_WithNullMessage_SetsNullMessage() {
+        // Act
+        InvalidTransactionException exception = new InvalidTransactionException(null);
+
+        // Assert
+        assertEquals(null, exception.getMessage());
+    }
+
+    @Test
+    void constructor_WithNullCause_SetsNullCause() {
+        // Act
+        InvalidTransactionException exception = new InvalidTransactionException("Invalid Transaction data", null);
+
+        // Assert
+        assertEquals(null, exception.getCause());
+    }
+
+    @Test
+    void throw_InvalidTransactionException() {
+        // Act and Assert
+        assertThrows(InvalidTransactionException.class, () -> {
+            throw new InvalidTransactionException("Invalid Transaction data");
+        });
+    }
+}