test: add smoke tests for defer importing synthetic modules

The tests added ensure that Node.js doesn't crash or produce
incorrect results when importing synthetic modules (i.e. JSON,
text or builtin modules) with the `defer` modifier.

Signed-off-by: Maya Lekova <maya@igalia.com>

Author: MayaLekova

test/es-module/test-defer-import-builtin-module.mjs

@@ -0,0 +1,22 @@
+// Flags:   js-defer-import-eval --experimental-import-text
+
+// Test that uses import.defer for a builtin module. Currently
+// defer importing of a synthetic module should be a no-op
+// in Node.js, so the test is mostly a smoke test that Node
+// doesn't crash.
+
+import '../common/index.mjs';
+import * as assert from 'assert';
+
+// Import the file system builtin module.
+import defer * as fs from 'node:fs';
+
+// Check that the imported module contains some known properties.
+assert.notStrictEqual(fs.constants, undefined);
+assert.notStrictEqual(fs.access, undefined);
+assert.strictEqual(typeof fs.access, 'function');
+
+// Check that the builtin module also exports some
+// usable contructor functions.
+assert.strictEqual(typeof fs.Stats, 'function');
+assert.strictEqual(typeof new fs.Stats(), 'object');

test/es-module/test-defer-import-json-module.mjs

@@ -0,0 +1,16 @@
+// Flags: --js-defer-import-eval
+
+// Test that uses import.defer for a JSON module. Currently
+// defer importing of a synthetic module should be a no-op
+// in Node.js, so the test is mostly a smoke test that Node
+// doesn't crash.
+
+import '../common/index.mjs';
+import * as assert from 'assert';
+
+import defer * as imported_json
+  from '../fixtures/json-with-directory-name-module/module-stub.json'
+  with { type: 'json' };
+
+// Check that the imported object has the expected key/value.
+assert.strictEqual(imported_json.default.rocko, 'artischocko');

test/es-module/test-defer-import-text-module.mjs

@@ -0,0 +1,18 @@
+// Flags: --js-defer-import-eval --experimental-import-text
+
+// Test that uses import.defer for a text module. Currently
+// defer importing of a synthetic module should be a no-op
+// in Node.js, so the test is mostly a smoke test that Node
+// doesn't crash.
+
+import '../common/index.mjs';
+import * as assert from 'assert';
+
+import defer * as imported_text
+  from '../fixtures/file-to-read-without-bom.txt'
+  with { type: 'text' };
+
+const expected_text = 'abc\ndef\nghi\n';
+
+// Check that the imported text has the expected value.
+assert.strictEqual(imported_text.default, expected_text);