fs: handle long files reading in fs.promises

PR-URL: https://github.com/nodejs/node/pull/19643
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

1 files changed, 28 insertions, 0 deletions

diff --git a/test/parallel/test-fs-promises-readfile.js b/test/parallel/test-fs-promises-readfile.js
new file mode 100644
index 0000000000..1bf49503c3
--- /dev/null
+++ b/test/parallel/test-fs-promises-readfile.js
@@ -0,0 +1,28 @@
+'use strict';
+
+const common = require('../common');
+
+const assert = require('assert');
+const path = require('path');
+const { writeFile, readFile } = require('fs/promises');
+const tmpdir = require('../common/tmpdir');
+tmpdir.refresh();
+
+const fn = path.join(tmpdir.path, 'large-file');
+
+common.crashOnUnhandledRejection();
+
+// Creating large buffer with random content
+const buffer = Buffer.from(
+  Array.apply(null, { length: 16834 * 2 })
+    .map(Math.random)
+    .map((number) => (number * (1 << 8)))
+);
+
+// Writing buffer to a file then try to read it
+writeFile(fn, buffer)
+  .then(() => readFile(fn))
+  .then((readBuffer) => {
+    assert.strictEqual(readBuffer.equals(buffer), true);
+  })
+  .then(common.mustCall());