test: cover bundle-size-summary.js and fail loudly on missing entrypoints

Addresses review feedback: validate every tracked entrypoint is present
in stats.json (fail instead of silently skipping) and add unit tests
for the summary script.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

superset-frontend/scripts/bundle-size-summary.js

@@ -59,7 +59,10 @@ function main() {
   const results = [];
   TRACKED_ENTRYPOINTS.forEach(name => {
     const entrypoint = entrypoints[name];
-    if (!entrypoint) return;
+    if (!entrypoint) {
+      console.error(`stats.json is missing the "${name}" entrypoint`);
+      process.exit(1);
+    }
     results.push({
       name: `${name} entrypoint (JS)`,
       unit: 'bytes',
@@ -75,4 +78,8 @@ function main() {
   console.log(JSON.stringify(results, null, 2));
 }
 
-main();
+if (require.main === module) {
+  main();
+}
+
+module.exports = { entrypointSizeByExt, main, TRACKED_ENTRYPOINTS };

superset-frontend/spec/scripts/bundle-size-summary.test.js

@@ -0,0 +1,107 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+const fs = require('fs');
+const {
+  entrypointSizeByExt,
+  main,
+} = require('../../scripts/bundle-size-summary');
+
+function mockStats(entrypoints) {
+  jest
+    .spyOn(fs, 'readFileSync')
+    .mockReturnValue(JSON.stringify({ entrypoints }));
+}
+
+function mockExit() {
+  return jest.spyOn(process, 'exit').mockImplementation(() => {
+    throw new Error('process.exit called');
+  });
+}
+
+afterEach(() => {
+  jest.restoreAllMocks();
+});
+
+test('entrypointSizeByExt sums only assets matching the given extension', () => {
+  const entrypoint = {
+    assets: [
+      { name: 'spa.entry.js', size: 100 },
+      { name: 'spa.entry.js.map', size: 500 },
+      { name: 'spa.entry.css', size: 20 },
+    ],
+  };
+  expect(entrypointSizeByExt(entrypoint, '.js')).toBe(100);
+  expect(entrypointSizeByExt(entrypoint, '.css')).toBe(20);
+});
+
+test('entrypointSizeByExt returns 0 when the entrypoint has no assets', () => {
+  expect(entrypointSizeByExt({}, '.js')).toBe(0);
+});
+
+test('main prints byte totals for every tracked entrypoint', () => {
+  mockStats({
+    spa: { assets: [{ name: 'spa.js', size: 100 }] },
+    embedded: { assets: [{ name: 'embedded.js', size: 50 }] },
+  });
+  const logSpy = jest.spyOn(console, 'log').mockImplementation(() => {});
+  process.argv = ['node', 'bundle-size-summary.js', 'stats.json'];
+
+  main();
+
+  const printed = JSON.parse(logSpy.mock.calls[0][0]);
+  expect(printed).toEqual([
+    { name: 'spa entrypoint (JS)', unit: 'bytes', value: 100 },
+    { name: 'spa entrypoint (CSS)', unit: 'bytes', value: 0 },
+    { name: 'embedded entrypoint (JS)', unit: 'bytes', value: 50 },
+    { name: 'embedded entrypoint (CSS)', unit: 'bytes', value: 0 },
+  ]);
+});
+
+test('main exits with an error when a tracked entrypoint is missing from stats.json', () => {
+  mockStats({ spa: { assets: [] } });
+  const errorSpy = jest.spyOn(console, 'error').mockImplementation(() => {});
+  mockExit();
+  process.argv = ['node', 'bundle-size-summary.js', 'stats.json'];
+
+  expect(main).toThrow('process.exit called');
+  expect(errorSpy).toHaveBeenCalledWith(
+    expect.stringContaining('missing the "embedded" entrypoint'),
+  );
+});
+
+test('main exits with an error when stats.json has no `entrypoints` key', () => {
+  jest.spyOn(fs, 'readFileSync').mockReturnValue(JSON.stringify({}));
+  const errorSpy = jest.spyOn(console, 'error').mockImplementation(() => {});
+  mockExit();
+  process.argv = ['node', 'bundle-size-summary.js', 'stats.json'];
+
+  expect(main).toThrow('process.exit called');
+  expect(errorSpy).toHaveBeenCalledWith(
+    expect.stringContaining('no `entrypoints` key'),
+  );
+});
+
+test('main prints a usage message and exits when no stats path is given', () => {
+  const errorSpy = jest.spyOn(console, 'error').mockImplementation(() => {});
+  mockExit();
+  process.argv = ['node', 'bundle-size-summary.js'];
+
+  expect(main).toThrow('process.exit called');
+  expect(errorSpy).toHaveBeenCalledWith(expect.stringContaining('Usage:'));
+});