nodejs/test/parallel/test-fs-promises-writefile-...

37 lines
995 B
JavaScript

'use strict';
/*
* This test makes sure that `writeFile()` always writes from the current
* position of the file, instead of truncating the file.
*/
const common = require('../common');
const assert = require('assert');
const path = require('path');
const { readFileSync } = require('fs');
const { open } = require('fs').promises;
const tmpdir = require('../common/tmpdir');
tmpdir.refresh();
const fn = path.join(tmpdir.path, 'test.txt');
async function writeFileTest() {
const handle = await open(fn, 'w');
/* Write only five bytes, so that the position moves to five. */
const buf = Buffer.from('Hello');
const { bytesWritten } = await handle.write(buf, 0, 5, null);
assert.strictEqual(bytesWritten, 5);
/* Write some more with writeFile(). */
await handle.writeFile('World');
/* New content should be written at position five, instead of zero. */
assert.deepStrictEqual(readFileSync(fn).toString(), 'HelloWorld');
}
writeFileTest()
.then(common.mustCall());