test: add mustCall to test-fs-readfile-pipe

PR-URL: #27450
Reviewed-By: Yorkie Liu <yorkiefixer@gmail.com>
Reviewed-By: Weijia Wang <starkwang@126.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

test/parallel/test-fs-readfile-pipe.js

@@ -31,10 +31,10 @@ const assert = require('assert');
 const fs = require('fs');
 
 if (process.argv[2] === 'child') {
-  fs.readFile('/dev/stdin', function(er, data) {
+  fs.readFile('/dev/stdin', common.mustCall(function(er, data) {
     assert.ifError(er);
     process.stdout.write(data);
-  });
+  }));
   return;
 }
 
@@ -47,7 +47,7 @@ const exec = require('child_process').exec;
 const f = JSON.stringify(__filename);
 const node = JSON.stringify(process.execPath);
 const cmd = `cat ${filename} | ${node} ${f} child`;
-exec(cmd, function(err, stdout, stderr) {
+exec(cmd, common.mustCall(function(err, stdout, stderr) {
   assert.ifError(err);
   assert.strictEqual(
     stdout,
@@ -58,4 +58,4 @@ exec(cmd, function(err, stdout, stderr) {
     '',
     `expected not to read anything from stderr but got: '${stderr}'`);
   console.log('ok');
-});
+}));