test: increase coverage for fs.promises.truncate

To increase test coverage, added tests for fs.promises.truncate and FileHandle.truncate. PR-URL: #20638 Reviewed-By: James M Snell <[email protected]> Reviewed-By: Ruben Bridgewater <[email protected]> Backport-PR-URL: #21172

Author: Masashi Hirano

test/parallel/test-fs-promises-file-handle-truncate.js

@@ -0,0 +1,26 @@
+'use strict';
+
+constcommon=require('../common');
+constassert=require('assert');
+constpath=require('path');
+const{ open, readFile }=require('fs').promises;
+consttmpdir=require('../common/tmpdir');
+
+tmpdir.refresh();
+common.crashOnUnhandledRejection();
+
+asyncfunctionvalidateTruncate(){
+consttext='Hello world';
+constfilename=path.resolve(tmpdir.path,'truncate-file.txt');
+constfileHandle=awaitopen(filename,'w+');
+
+constbuffer=Buffer.from(text,'utf8');
+awaitfileHandle.write(buffer,0,buffer.length);
+
+assert.deepStrictEqual((awaitreadFile(filename)).toString(),text);
+
+awaitfileHandle.truncate(5);
+assert.deepStrictEqual((awaitreadFile(filename)).toString(),'Hello');
+}
+
+validateTruncate().then(common.mustCall());

test/parallel/test-fs-promises.js

@@ -17,13 +17,15 @@ const{
  mkdir,
  mkdtemp,
  open,
+ readFile,
  readdir,
  readlink,
  realpath,
  rename,
  rmdir,
  stat,
  symlink,
+ truncate,
  unlink,
  utimes
 }=fsPromises;
@@ -99,6 +101,8 @@ function verifyStatObject(stat){
 constret2=awaithandle.read(Buffer.alloc(buf2Len),0,buf2Len,0);
 assert.strictEqual(ret2.bytesRead,buf2Len);
 assert.deepStrictEqual(ret2.buffer,buf2);
+awaittruncate(dest,5);
+assert.deepStrictEqual((awaitreadFile(dest)).toString(),'hello');
 
 awaitchmod(dest,0o666);
 awaithandle.chmod(0o666);