Add unit testing support with vitest (#18)

* update loose files and add vitest

* update test scripts

* more support for vitest

* more test support

* update vscode settings

src/test/phaser.setup.ts

@@ -0,0 +1,5 @@
+import Phaser from "phaser";
+
+export default new Phaser.Game({
+  type: Phaser.HEADLESS,
+});

src/test/vitest.setup.ts

@@ -0,0 +1,2 @@
+import "vitest-canvas-mock";
+import "#app/test/phaser.setup";

src/utils.test.ts

@@ -0,0 +1,22 @@
+import { expect, describe, it } from "vitest";
+import { randomString } from "./utils";
+
+import Phaser from "phaser";
+
+describe("utils", () => {
+  describe("randomString", () => {
+    it("should return a string of the specified length", () => {
+      const str = randomString(10);
+      expect(str.length).toBe(10);
+    });
+
+    it("should work with seed", () => {
+      const state = Phaser.Math.RND.state();
+      const str1 = randomString(10, true);
+      Phaser.Math.RND.state(state);
+      const str2 = randomString(10, true);
+
+      expect(str1).toBe(str2);
+    });
+  });
+});