test: add tests for states

tests/unit/states/theme.test.ts

@@ -0,0 +1,49 @@
+import { describe, expect, it } from "vitest";
+import { themeState } from "$states/theme.svelte";
+
+describe("theme.svelte", () => {
+  describe("initial state", () => {
+    it("should have initial theme", () => {
+      expect(themeState.theme).toBeDefined();
+      expect(["light", "dark"]).toContain(themeState.theme);
+    });
+
+    it("should start with dark theme by default", () => {
+      expect(themeState.theme).toBe("dark");
+    });
+  });
+
+  describe("toggle", () => {
+    it("should toggle between light and dark themes", () => {
+      const initialTheme = themeState.theme;
+
+      themeState.toggle();
+      expect(themeState.theme).not.toBe(initialTheme);
+
+      themeState.toggle();
+      expect(themeState.theme).toBe(initialTheme);
+    });
+
+    it("should switch from dark to light", () => {
+      themeState.theme = "dark";
+      themeState.toggle();
+      expect(themeState.theme).toBe("light");
+    });
+
+    it("should switch from light to dark", () => {
+      themeState.theme = "light";
+      themeState.toggle();
+      expect(themeState.theme).toBe("dark");
+    });
+  });
+
+  describe("theme getter", () => {
+    it("should return current theme", () => {
+      themeState.theme = "dark";
+      expect(themeState.theme).toBe("dark");
+
+      themeState.theme = "light";
+      expect(themeState.theme).toBe("light");
+    });
+  });
+});