Resolve Electron binary directly at startup

tests/unit/electron-launcher.test.js

@@ -0,0 +1,59 @@
+'use strict';
+
+const test = require('node:test');
+const assert = require('node:assert/strict');
+const fs = require('node:fs');
+const path = require('node:path');
+
+const {
+  buildMissingElectronError,
+  resolveElectronBinary,
+} = require('../../scripts/electron-launcher');
+const { makeTmpDir, rmrf } = require('./helpers');
+
+test('resolves the Electron binary from path.txt when present', (t) => {
+  const root = makeTmpDir('electron-path-hint');
+  t.after(() => rmrf(root));
+
+  fs.mkdirSync(path.join(root, 'dist'), { recursive: true });
+  fs.writeFileSync(path.join(root, 'path.txt'), 'electron.exe\n');
+  fs.writeFileSync(path.join(root, 'dist', 'electron.exe'), 'binary');
+
+  assert.equal(
+    resolveElectronBinary({ packageRoot: root, platform: 'win32' }),
+    path.join(root, 'dist', 'electron.exe')
+  );
+});
+
+test('falls back to the platform binary when path.txt is absent', (t) => {
+  const root = makeTmpDir('electron-platform-fallback');
+  t.after(() => rmrf(root));
+
+  fs.mkdirSync(path.join(root, 'dist'), { recursive: true });
+  fs.writeFileSync(path.join(root, 'dist', 'electron.exe'), 'binary');
+
+  assert.equal(
+    resolveElectronBinary({ packageRoot: root, platform: 'win32' }),
+    path.join(root, 'dist', 'electron.exe')
+  );
+});
+
+test('reports a helpful error when the runtime is missing', (t) => {
+  const root = makeTmpDir('electron-missing');
+  t.after(() => rmrf(root));
+
+  fs.mkdirSync(path.join(root, 'dist'), { recursive: true });
+
+  assert.throws(
+    () => resolveElectronBinary({ packageRoot: root, platform: 'win32' }),
+    /npm install/
+  );
+
+  const message = buildMissingElectronError({
+    packageRoot: root,
+    distDir: path.join(root, 'dist'),
+    candidatePaths: [path.join(root, 'dist', 'electron.exe')],
+  });
+  assert.match(message, /Electron could not be started/);
+  assert.match(message, /Expected the binary in:/);
+});