test: add test for ERR_AMBIGUOUS_MODULE_SYNTAX

Author: Divya9877

test/es-module/test-ambiguous-module-syntax.js

@@ -0,0 +1,31 @@
+'use strict';
+
+const common = require('../common');
+const assert = require('assert');
+const { spawnSync } = require('child_process');
+const fixtures = require('../common/fixtures');
+
+// Skip if ESM is not supported in this environment
+common.skipIfESMUnsupported(__filename);
+
+// Fixture that mixes CJS + ESM
+const entry = fixtures.path('es-modules', 'ambiguous-mixed-syntax.js');
+
+const result = spawnSync(process.execPath, [entry], {
+  encoding: 'utf8'
+});
+
+// Node should exit with an error
+assert.notStrictEqual(result.status, 0);
+
+// Error code must be present
+assert.ok(
+  /ERR_AMBIGUOUS_MODULE_SYNTAX/.test(result.stderr),
+  `stderr did not contain ERR_AMBIGUOUS_MODULE_SYNTAX:\n${result.stderr}`
+);
+
+// Your new explanatory message should appear
+assert.ok(
+  /mixes CommonJS/.test(result.stderr),
+  `stderr did not contain expected message:\n${result.stderr}`
+);

test/fixtures/es-modules/ambiguous-mixed-syntax.js

@@ -0,0 +1,8 @@
+// This file intentionally mixes CommonJS and ES Module syntax
+// to trigger ERR_AMBIGUOUS_MODULE_SYNTAX.
+
+// CommonJS
+const fs = require('fs');
+
+// ES Modules
+export const value = 123;