implement junit tests

src/test/java/ModuloTest.java

@@ -0,0 +1,20 @@
+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;
+
+import de.hsrm.compiler.Klang.ContextAnalysis;
+
+public class ModuloTest {
+    @Test
+    void onlyForInt() {
+        ParseTree tree = Helper.prepareParser("function foo(): float { return 1.0 % 2.3; } foo();");
+        var funcs = Helper.getFuncs(tree);
+        var structs = Helper.getStructs(tree);
+        ContextAnalysis ctxAnal = new ContextAnalysis(funcs, structs);
+        
+        Exception e = assertThrows(RuntimeException.class, () -> ctxAnal.visit(tree));
+        assertEquals("Error in line 1:31 Only integers are allowed for modulo.", e.getMessage());
+    }
+}