Added tests for UniformTileGenerator

src/test/java/model/UniformTileGeneratorTest.java

+package model;
+
+import javafx.scene.paint.Color;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class UniformTileGeneratorTest {
+  @Test
+  void testNextTile(){
+    TileGenerator tileGenerator = new UniformTileGenerator(Color.RED);
+    Tile redTile = new UniformTile(new ColoredSide(Color.RED));
+    for(int index = 0; index < 10; index++)
+      assertThat(tileGenerator.nextTile(EmptySquare.EMPTY_SQUARE)).isEqualTo(redTile);
+  }
+}