test: exercise real Python discovery failure controls

tests/lib/windows-test-env.test.js

@@ -10,11 +10,24 @@ const assert = require('assert');
 const fs = require('fs');
 const os = require('os');
 const path = require('path');
+const vm = require('vm');
 
 const { test, banner, summary } = require('./helpers/mini-test-runner');
 const { spawnSync } = require('child_process');
 const { withoutShadowingClaude, toRelativeTarPath, resolvePython } = require('./helpers/windows-test-env');
 
+/** Load the unchanged helper with controlled process results, keeping its real probe. */
+function loadWithSpawn(spawn) {
+  const filename = path.join(__dirname, 'helpers', 'windows-test-env.js');
+  const module = { exports: {} };
+  vm.runInNewContext(fs.readFileSync(filename, 'utf8'), {
+    module,
+    require: name => name === 'child_process' ? { spawnSync: spawn } : require(name),
+    process,
+  }, { filename });
+  return module.exports;
+}
+
 banner('windows-test-env helper');
 
 let passed = 0;
@@ -76,6 +89,51 @@ try {
     assert.strictEqual(resolvePython({ platform: 'linux', probe: () => false }), null);
   })) passed++; else failed++;
 
+  if (test('real probe accepts success and preserves Windows launcher arguments', () => {
+    const calls = [];
+    const helper = loadWithSpawn((command, args, options) => {
+      calls.push({ command, args: Array.from(args), options: { ...options } });
+      return { status: command === 'py' ? 0 : 9009 };
+    });
+    const python = helper.resolvePython({ platform: 'win32' });
+    assert.strictEqual(python.command, 'py');
+    assert.deepStrictEqual(Array.from(python.prefix), ['-3']);
+    assert.deepStrictEqual(calls.map(call => call.command), ['python', 'py']);
+    assert.deepStrictEqual(calls[1].args.slice(0, 2), ['-3', '-c']);
+    assert.deepStrictEqual(calls[1].options, { encoding: 'utf8', timeout: 15000 });
+  })) passed++; else failed++;
+
+  if (test('real probe rejects nonzero, missing commands and timed out processes', () => {
+    for (const result of [
+      { status: 1 },
+      { status: 9009 },
+      { status: null, error: Object.assign(new Error('not found'), { code: 'ENOENT' }) },
+      { status: null, error: Object.assign(new Error('timed out'), { code: 'ETIMEDOUT' }) },
+    ]) {
+      const calls = [];
+      const helper = loadWithSpawn(command => { calls.push(command); return result; });
+      assert.strictEqual(helper.resolvePython({ platform: 'win32' }), null);
+      assert.deepStrictEqual(calls, ['python', 'py', 'python3']);
+    }
+  })) passed++; else failed++;
+
+  if (test('real probe code succeeds under known Python 3 and rejects Python 2', () => {
+    // Select independently so broken discovery cannot silently skip this control.
+    const known = [['python3'], ['python'], ['py', '-3']].find(([command, ...prefix]) => {
+      const result = spawnSync(command, [...prefix, '-c', 'import sys; print(sys.version_info[0])'], { encoding: 'utf8', timeout: 15000 });
+      return result.status === 0 && result.stdout.trim() === '3';
+    });
+    assert.ok(known, 'Python 3 is required for the Hermes test workflow');
+    for (const [major, expected] of [[3, true], [2, false]]) {
+      const helper = loadWithSpawn((_command, args, options) => {
+        const code = args[args.indexOf('-c') + 1];
+        const wrapped = `import sys; sys.version_info = (${major}, 0);\n${code}`;
+        return spawnSync(known[0], [...known.slice(1), '-c', wrapped], options);
+      });
+      assert.strictEqual(helper.resolvePython({ platform: 'win32' }) !== null, expected);
+    }
+  })) passed++; else failed++;
+
   if (test('a resolved interpreter actually runs Python 3 here', () => {
     const python = resolvePython();
     if (!python) return;