add a transform test for app.js

lib/transforms/app.test.js

@@ -0,0 +1,64 @@
+import { parse, print } from 'recast';
+import babelParser from 'recast/parsers/babel.js';
+import { describe, it, expect, vi } from 'vitest';
+import transformApp from './app.js';
+
+vi.mock('../utils/get-app-name', async () => {
+  return {
+    getAppName: () => 'fancy-app',
+  };
+});
+
+async function parseAndApply(input) {
+  let ast = await parse(input, { parser: babelParser });
+  ast = await transformApp(ast);
+  return print(ast).code;
+}
+
+describe('transformApp() function', () => {
+  it('transforms a default app.js', async () => {
+    expect(
+      await parseAndApply(
+        `
+import Application from '@ember/application';
+import Resolver from 'ember-resolver';
+import loadInitializers from 'ember-load-initializers';
+import config from 'my-app/config/environment';
+import { importSync, isDevelopingApp, macroCondition } from '@embroider/macros';
+
+if (macroCondition(isDevelopingApp())) {
+  importSync('./deprecation-workflow');
+}
+
+export default class App extends Application {
+  modulePrefix = config.modulePrefix;
+  podModulePrefix = config.podModulePrefix;
+  Resolver = Resolver;
+}
+
+loadInitializers(App, config.modulePrefix);`,
+      ),
+    ).toMatchInlineSnapshot(`
+      "
+      import Application from '@ember/application';
+      import Resolver from 'ember-resolver';
+      import loadInitializers from 'ember-load-initializers';
+      import config from 'my-app/config/environment';
+      import { importSync, isDevelopingApp, macroCondition } from '@embroider/macros';
+
+      import compatModules from "@embroider/virtual/compat-modules";
+
+      if (macroCondition(isDevelopingApp())) {
+        importSync('./deprecation-workflow');
+      }
+
+      export default class App extends Application {
+        modulePrefix = config.modulePrefix;
+        podModulePrefix = config.podModulePrefix;
+        Resolver = Resolver.withModules(compatModules);
+      }
+
+      loadInitializers(App, config.modulePrefix, compatModules);"
+    `);
+  });
+});