diff --git a/spec/javascript/channels/consumer_spec.ts b/spec/javascript/channels/consumer_spec.ts
new file mode 100644
index 000000000..ccfee3749
--- /dev/null
+++ b/spec/javascript/channels/consumer_spec.ts
@@ -0,0 +1,6 @@
+import {expect, it} from "vitest";
+import consumer from "channels/consumer";
+
+it("is defined", () => {
+  expect(consumer.url).toBe("ws://test.host/cable");
+});
diff --git a/spec/javascript/controllers/dialog_controller_spec.ts b/spec/javascript/controllers/dialog_controller_spec.ts
new file mode 100644
index 000000000..35954f6ad
--- /dev/null
+++ b/spec/javascript/controllers/dialog_controller_spec.ts
@@ -0,0 +1,10 @@
+import {expect, it} from "vitest";
+import {bootStimulus} from "spec/javascript/support/stimulus";
+import DialogController from "controllers/dialog_controller";
+
+it("updates the text content of its element", async () => {
+  document.body.innerHTML = "<div data-controller='dialog'></div>";
+  await bootStimulus("dialog", DialogController);
+
+  expect(document.body.textContent).toBe("Hello World!");
+});
diff --git a/spec/javascript/controllers/hotkeys_controller_spec.ts b/spec/javascript/controllers/hotkeys_controller_spec.ts
new file mode 100644
index 000000000..c4654def5
--- /dev/null
+++ b/spec/javascript/controllers/hotkeys_controller_spec.ts
@@ -0,0 +1,74 @@
+import {describe, expect, it, vi} from "vitest";
+import {bootStimulus, getController} from "spec/javascript/support/stimulus";
+import HotkeysController from "controllers/hotkeys_controller";
+import {assert} from "javascript/helpers";
+
+function setupDOM(): void {
+  document.body.innerHTML = `
+    <div data-controller="hotkeys">
+      <button data-hotkeys-target="click" data-hotkey="a">A</button>
+    </div>
+  `;
+}
+
+async function setupController(): Promise<void> {
+  setupDOM();
+
+  await bootStimulus("hotkeys", HotkeysController);
+}
+
+function element(): HTMLElement {
+  const selector = "[data-controller='hotkeys']";
+
+  return assert(document.querySelector<HTMLElement>(selector));
+}
+
+function controller(): HotkeysController {
+  return getController(element(), "hotkeys", HotkeysController);
+}
+
+function button(): HTMLButtonElement {
+  const selector = "button[data-hotkeys-target='click']";
+
+  return assert(document.querySelector<HTMLButtonElement>(selector));
+}
+
+describe("clickTargetConnected", () => {
+  it("indexes the connected click target by its hotkey", async () => {
+    await setupController();
+
+    expect(controller().indexedClickTargets.get("a")).toBe(button());
+  });
+});
+
+describe("clickTargetDisconnected", () => {
+  it("removes the disconnected click target from the index", async () => {
+    await setupController();
+
+    button().remove();
+
+    await Promise.resolve();
+
+    expect(controller().indexedClickTargets.get("a")).toBeUndefined();
+  });
+});
+
+describe("handleKeydown", () => {
+  it("clicks the target for the pressed key", async () => {
+    await setupController();
+    const clickSpy = vi.spyOn(button(), "click");
+
+    controller().handleKeydown(new KeyboardEvent("keydown", {key: "a"}));
+
+    expect(clickSpy).toHaveBeenCalledWith();
+  });
+
+  it("does nothing if there is no target for the pressed key", async () => {
+    await setupController();
+    const clickSpy = vi.spyOn(button(), "click");
+
+    controller().handleKeydown(new KeyboardEvent("keydown", {key: "b"}));
+
+    expect(clickSpy).not.toHaveBeenCalled();
+  });
+});
diff --git a/spec/javascript/helpers/assert_spec.ts b/spec/javascript/helpers/assert_spec.ts
new file mode 100644
index 000000000..233d83557
--- /dev/null
+++ b/spec/javascript/helpers/assert_spec.ts
@@ -0,0 +1,33 @@
+import {describe, expect, it} from "vitest";
+import {assert} from "javascript/helpers";
+
+describe("assert", () => {
+  it("throws an error when the passed value is null", () => {
+    expect(() => { assert(null); }).toThrow("value is null or undefined");
+  });
+
+  it("throws an error when the passed value is undefined", () => {
+    expect(() => { assert(undefined); }).toThrow("value is null or undefined");
+  });
+
+  it("does not throw an error when the passed value is 0", () => {
+    expect(() => { assert(0); }).not.toThrow();
+  });
+
+  it("does not throw an error when the passed value is false", () => {
+    expect(() => { assert(false); }).not.toThrow();
+  });
+
+  it("does not throw an error when the passed value is empty string", () => {
+    expect(() => { assert(""); }).not.toThrow();
+  });
+
+  it("returns the passed value", () => {
+    expect(assert("blah")).toBe("blah");
+    expect(assert(0)).toBe(0);
+
+    const obj = {bloo: "blah"};
+
+    expect(assert(obj)).toBe(obj);
+  });
+});
diff --git a/spec/javascript/support/stimulus.ts b/spec/javascript/support/stimulus.ts
new file mode 100644
index 000000000..be29ca49b
--- /dev/null
+++ b/spec/javascript/support/stimulus.ts
@@ -0,0 +1,46 @@
+import {afterEach} from "vitest";
+import type {Context, Controller} from "@hotwired/stimulus";
+import {Application} from "@hotwired/stimulus";
+
+import {assert} from "javascript/helpers";
+
+let application: Application | null = null;
+
+type ControllerClass<T> = new (context: Context) => T;
+
+async function bootStimulus<T extends Controller>(
+  name: string,
+  controller: ControllerClass<T>,
+): Promise<void> {
+  application ??= Application.start();
+
+  application.register(name, controller);
+  application.handleError = (error: Error): void => { throw error; };
+
+  await Promise.resolve();
+}
+
+function getController<T extends Controller>(
+  element: HTMLElement,
+  name: string,
+  controllerClass: ControllerClass<T>,
+): T {
+  const controller =
+    assert(application).getControllerForElementAndIdentifier(element, name);
+
+  if (controller instanceof controllerClass) {
+    return controller;
+  } else if (controller) {
+    throw new Error("Controller class does not match");
+  }
+
+  throw new Error("Controller not found");
+}
+
+afterEach(() => {
+  if (application) { application.stop(); }
+
+  application = null;
+});
+
+export {bootStimulus, getController};
diff --git a/spec/javascript/vitest-globals.d.ts b/spec/javascript/vitest-globals.d.ts
new file mode 100644
index 000000000..9896c472f
--- /dev/null
+++ b/spec/javascript/vitest-globals.d.ts
@@ -0,0 +1 @@
+/// <reference types="vitest/globals" />
diff --git a/tsconfig.json b/tsconfig.json
index 0446d3a36..81a6a4a58 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -23,6 +23,7 @@
       "_test_helpers/*": ["spec/javascript/_test_helpers/*"],
       "controllers/*": ["app/javascript/controllers/*"]
     },
+    "skipLibCheck": true,
     "sourceMap": true,
     "strict": true,
     "target": "es6",