fix: rewrite .js to .ts imports in test files

Test files import from source using .js extensions which don't
resolve on Node 24 with module:nodenext. Apply the same .js -> .ts
import rewrite to test files as was done for source files.

Assisted-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: bennypowers

packages/browser-logs/test/serialize-deserialize.test.ts

@@ -3,7 +3,7 @@ import puppeteer, { Browser, Page } from 'puppeteer';
 import fs from 'fs';
 import path from 'path';
 
-import { deserialize } from '../src/deserialize.js';
+import { deserialize } from '../src/deserialize.ts';
 
 const serializeScript = fs.readFileSync(require.resolve('../dist/serialize.js'), 'utf-8');
 const defaultOptions = { browserRootDir: __dirname, cwd: __dirname };

packages/dev-server-core/test/middleware/basePathMiddleware.test.ts

@@ -1,7 +1,7 @@
 import { expect } from 'chai';
 
-import { DevServer } from '../../src/server/DevServer.js';
-import { createTestServer } from '../helpers.js';
+import { DevServer } from '../../src/server/DevServer.ts';
+import { createTestServer } from '../helpers.ts';
 
 describe('base path middleware', () => {
   describe('without a trailing /', () => {

packages/dev-server-core/test/middleware/etagCacheMiddleware.test.ts

@@ -3,8 +3,8 @@ import path from 'path';
 import fs from 'fs';
 import { nanoid } from 'nanoid';
 
-import { createTestServer, timeout } from '../helpers.js';
-import { DevServer } from '../../src/server/DevServer.js';
+import { createTestServer, timeout } from '../helpers.ts';
+import { DevServer } from '../../src/server/DevServer.ts';
 
 const fixtureDir = path.resolve(__dirname, '..', 'fixtures', 'basic');
 const testFileAName = '/cached-file-a.js';

packages/dev-server-core/test/middleware/pluginFileParsedMiddleware.test.ts

@@ -1,7 +1,7 @@
 import { expect } from 'chai';
 import { Context } from 'koa';
 
-import { createTestServer } from '../helpers.js';
+import { createTestServer } from '../helpers.ts';
 
 describe('plugin-file-parsed middleware', () => {
   it('is called after other plugin hooks', async () => {

packages/dev-server-core/test/middleware/pluginMimeTypeMiddleware.test.ts

@@ -1,6 +1,6 @@
 import { expect } from 'chai';
 
-import { createTestServer } from '../helpers.js';
+import { createTestServer } from '../helpers.ts';
 
 describe('plugin-mime-type middleware', () => {
   it('can set the mime type of a file with a string', async () => {

packages/dev-server-core/test/middleware/pluginServeMiddleware.test.ts

@@ -1,6 +1,6 @@
 import { expect } from 'chai';
 
-import { createTestServer } from '../helpers.js';
+import { createTestServer } from '../helpers.ts';
 
 describe('plugin-serve middleware', () => {
   it('can serve non-existing files', async () => {

packages/dev-server-core/test/middleware/pluginTransformMiddleware.test.ts

@@ -1,8 +1,8 @@
 /* eslint-disable no-restricted-syntax, no-await-in-loop */
 import { expect } from 'chai';
 
-import { createTestServer } from '../helpers.js';
-import { fetchText, expectIncludes } from '../../src/test-helpers.js';
+import { createTestServer } from '../helpers.ts';
+import { fetchText, expectIncludes } from '../../src/test-helpers.ts';
 
 describe('plugin-transform middleware', () => {
   it('can transform a served file', async () => {

packages/dev-server-core/test/plugins/transformModuleImportsPlugin.test.ts

@@ -1,8 +1,8 @@
 import { expect } from 'chai';
 
-import { transformImports } from '../../src/plugins/transformModuleImportsPlugin.js';
-import type { PluginSyntaxError } from '../../src/logger/PluginSyntaxError.js';
-import { createTestServer } from '../helpers.js';
+import { transformImports } from '../../src/plugins/transformModuleImportsPlugin.ts';
+import type { PluginSyntaxError } from '../../src/logger/PluginSyntaxError.ts';
+import { createTestServer } from '../helpers.ts';
 
 const defaultFilePath = '/root/my-file.js';
 const defaultResolveImport = (src: string) => `RESOLVED__${src}`;

packages/dev-server-core/test/server/DevServer.test.ts

@@ -6,9 +6,9 @@ import { FSWatcher } from 'chokidar';
 import { expect } from 'chai';
 import portfinder from 'portfinder';
 import { Stub, stubMethod } from 'hanbi';
-import { ServerStartParams } from '../../src/plugins/Plugin.js';
-import { DevServer } from '../../src/server/DevServer.js';
-import { createTestServer } from '../helpers.js';
+import { ServerStartParams } from '../../src/plugins/Plugin.ts';
+import { DevServer } from '../../src/server/DevServer.ts';
+import { createTestServer } from '../helpers.ts';
 
 describe('basic', () => {
   let host: string;

packages/dev-server-core/test/web-sockets/WebSocketsManager.test.ts

@@ -1,8 +1,8 @@
 import { expect } from 'chai';
 import WebSocket from 'ws';
-import { NAME_WEB_SOCKET_API } from '../../src/web-sockets/WebSocketsManager.js';
+import { NAME_WEB_SOCKET_API } from '../../src/web-sockets/WebSocketsManager.ts';
 
-import { createTestServer } from '../helpers.js';
+import { createTestServer } from '../helpers.ts';
 
 function waitFor(fn: (resolve: () => void) => void, msg: string) {
   return new Promise<void>((resolve, reject) => {