Restore App entry point and basic tests from main

Author: viktorlindell12

src/main/java/org/example/App.java

@@ -0,0 +1,7 @@
+package org.example;
+
+public class App {
+    public static void main(String[] args) {
+        new TcpServer(8080).start();
+    }
+}

src/test/java/org/example/AppIT.java

@@ -0,0 +1,12 @@
+package org.example;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class AppIT {
+    @Test
+    void itTest() {
+        assertThat(false).isFalse();
+    }
+}

src/test/java/org/example/AppTest.java

@@ -0,0 +1,12 @@
+package org.example;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class AppTest {
+    @Test
+    void test() {
+        assertThat(true).isTrue();
+    }
+}