[ascii] Test graphics backend, first unit test

projects/asciilib2/test/src/cases/DrawOnlyWhenModifiedTestCase.hx

@@ -0,0 +1,36 @@
+package cases;
+
+import utest.Test;
+import utest.Assert;
+import asciilib.GameLogic;
+import asciilib.Game;
+import asciilib.Graphics;
+import asciilib.Colors;
+import asciilib.backends.test.TestGraphicsBackend;
+
+class DrawOnlyWhenModifiedGameLogic implements GameLogic {
+    var firstDraw = true;
+
+    public function new() {}
+
+    public function update(deltaSeconds:Float):Void {}
+
+    public function draw(graphics:Void->Graphics):Void {
+        if (firstDraw) {
+            graphics().setLetter(0, 0, {char: "@", color: Colors.Red});
+            firstDraw = false;
+        }
+    }
+}
+
+class DrawOnlyWhenModifiedTestCase extends Test {
+    function testDrawOnlyWhenModified() {
+        var game = Main.newGame(new DrawOnlyWhenModifiedGameLogic());
+        var graphicsBackend:TestGraphicsBackend = cast game.graphicsBackend;
+        game.draw();
+        Assert.equals("@", game.graphics.getLetter(0, 0).char);
+        Assert.equals(1, graphicsBackend.drawCalled);
+        game.draw();
+        Assert.equals(1, graphicsBackend.drawCalled);
+    }
+}