Added GameManager and check if GameState is correct after start function call

src/main/java/de/tims/fleetstorm/GameManager.java

@@ -0,0 +1,19 @@
+package de.tims.fleetstorm;
+
+public class GameManager {
+
+	private int gameState;
+
+	public static final int PREPARATION = 1;
+	public static final int RUNNING = 2;
+	public static final int OVER = 3;
+
+	public void start() {
+		this.gameState = GameManager.PREPARATION;
+	}
+
+	public int getGameState() {
+		return gameState;
+	}
+
+}

src/test/java/de/tims/fleetstorm/GameManagerTest.java

@@ -0,0 +1,21 @@
+package de.tims.fleetstorm;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+class GameManagerTest {
+
+	GameManager gameManager = new GameManager();
+
+	@Test
+	void testIfGameStateIsPreparationAfterStart() {
+		gameManager.start();
+		int expectedState = GameManager.PREPARATION;
+
+		int calculatedState = gameManager.getGameState();
+
+		assertEquals(expectedState, calculatedState);
+	}
+
+}