implement junit tests

src/test/java/ParameterTest.java

@@ -0,0 +1,14 @@
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import org.antlr.v4.runtime.tree.ParseTree;
+import org.junit.jupiter.api.Test;
+
+public class ParameterTest {
+    @Test
+    void typeNotDefined() {
+        ParseTree tree = Helper.prepareParser("struct test { a: schwurbel; } function foo(): int { return 1; } foo();");
+        Exception e = assertThrows(RuntimeException.class, () -> Helper.getStructs(tree));
+        assertEquals("Error in line 1:14 Type schwurbel not defined.", e.getMessage());
+    }
+}