diff -r 627e1c99bcf1 -r a95423d37588 src/test/java/de/uapcore/sudoku/SudokuTest.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/test/java/de/uapcore/sudoku/SudokuTest.java	Tue Jul 28 13:48:59 2020 +0200
@@ -0,0 +1,41 @@
+package de.uapcore.sudoku;
+
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import javax.swing.*;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class SudokuTest {
+
+    private Sudoku subject;
+
+    @BeforeEach
+    void init() {
+        subject = new Sudoku();
+    }
+
+    @AfterEach
+    void destroy() {
+        subject.setDefaultCloseOperation(WindowConstants.DO_NOTHING_ON_CLOSE);
+        subject.dispose();
+    }
+
+    @Test
+    void testDefaultCloseOperation() {
+        assertEquals(WindowConstants.EXIT_ON_CLOSE, subject.getDefaultCloseOperation());
+    }
+
+    @Test
+    void testMinimumSize() {
+        assertEquals(subject.getSize(), subject.getMinimumSize());
+    }
+
+    @Test
+    void testLocationByPlattform() {
+        assertTrue(subject.isLocationByPlatform());
+    }
+}