• test/bake/bake-harness.ts - shared utilities: devTest, prodTest, devAndProductionTest, Dev class, Client class
• test/bake/client-fixture.mjs - subprocess for Client (page loading, IPC queries)
• test/bake/dev/*.test.ts - dev server and hot reload tests
• test/bake/dev-and-prod.ts - tests running on both dev and production mode

• bundle.test.ts - DevServer-specific bundling bugs
• css.test.ts - CSS bundling issues
• plugins.test.ts - development mode plugins
• ecosystem.test.ts - library compatibility (prefer concrete bugs over full package tests)
• esm.test.ts - ESM features in development
• html.test.ts - HTML file handling
• react-spa.test.ts - React, react-refresh transform, server components
• sourcemap.test.ts - source map correctness

```ts

import { devTest, emptyHtmlFile } from "../bake-harness";

devTest("html file is watched", {

files: {

"index.html": emptyHtmlFile({

scripts: ["/script.ts"],

body: "

Hello

}),

"script.ts": console.log("hello");,

},

async test(dev) {

await dev.fetch("/").expect.toInclude("

Hello

await dev.patch("index.html", { find: "Hello", replace: "World" });

await dev.fetch("/").expect.toInclude("

World

await using c = await dev.client("/");

await c.expectMessage("hello");

await c.expectReload(async () => {

await dev.patch("index.html", { find: "World", replace: "Bar" });

});

await c.expectMessage("hello");

},

});

```

• files: Initial filesystem state
• dev.fetch(): HTTP requests
• dev.client(): Opens browser instance
• dev.write/patch/delete: Filesystem mutations (wait for hot-reload automatically)
• c.expectMessage(): Assert console.log output
• c.expectReload(): Wrap code that causes hard reload

Important: Use dev.write/patch/delete instead of node:fs - they wait for hot-reload.

```ts

devTest("import then create", {

files: {

"index.html": ,

"script.ts": import data from "./data"; console.log(data);,

},

async test(dev) {

const c = await dev.client("/", {

errors: ['script.ts:1:18: error: Could not resolve: "./data"'],

});

await c.expectReload(async () => {

await dev.write("data.ts", "export default 'data';");

});

await c.expectMessage("data");

},

});

```

Specify expected errors with the errors option:

```ts

await dev.delete("other.ts", {

errors: ['index.ts:1:16: error: Could not resolve: "./other"'],

});

```