test: reduce string concatenations

PR-URL: https://github.com/nodejs/node/pull/12735 Refs: https://github.com/nodejs/node/pull/12455 Reviewed-By: Refael Ackermann <refack@gmail.com> Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
8 years ago · 8b76c3e60c
350 changed files with 1001 additions and 1075 deletions
--- a/test/addons/repl-domain-abort/test.js
+++ b/test/addons/repl-domain-abort/test.js
@ -39,7 +39,7 @@ process.on('exit', function() {
 const lines = [
  // This line shouldn't cause an assertion error.
-  'require(\'' + buildPath + '\')' +
+  `require('${buildPath}')` +
  // Log output to double check callback ran.
  '.method(function() { console.log(\'cb_ran\'); });',
 ];
--- a/test/common/index.js
+++ b/test/common/index.js
@ -55,9 +55,8 @@ exports.isLinux = process.platform === 'linux';
 exports.isOSX = process.platform === 'darwin';
 exports.enoughTestMem = os.totalmem() > 0x40000000; /* 1 Gb */
-exports.bufferMaxSizeMsg = new RegExp('^RangeError: "size" argument' +
+exports.bufferMaxSizeMsg = new RegExp(
-                                      ' must not be larger than ' +
+  `^RangeError: "size" argument must not be larger than ${buffer.kMaxLength}$`);
                                      buffer.kMaxLength + '$');
 const cpus = os.cpus();
 exports.enoughTestCpu = Array.isArray(cpus) &&
                        (cpus.length > 1 || cpus[0].speed > 999);
@ -118,7 +117,7 @@ exports.refreshTmpDir = function() {
 if (process.env.TEST_THREAD_ID) {
  exports.PORT += process.env.TEST_THREAD_ID * 100;
-  exports.tmpDirName += '.' + process.env.TEST_THREAD_ID;
+  exports.tmpDirName += `.${process.env.TEST_THREAD_ID}`;
 }
 exports.tmpDir = path.join(testRoot, exports.tmpDirName);
@ -217,10 +216,10 @@ Object.defineProperty(exports, 'hasFipsCrypto', {
 if (exports.isWindows) {
  exports.PIPE = '\\\\.\\pipe\\libuv-test';
  if (process.env.TEST_THREAD_ID) {
-    exports.PIPE += '.' + process.env.TEST_THREAD_ID;
+    exports.PIPE += `.${process.env.TEST_THREAD_ID}`;
  }
 } else {
-  exports.PIPE = exports.tmpDir + '/test.sock';
+  exports.PIPE = `${exports.tmpDir}/test.sock`;
 }
 const ifaces = os.networkInterfaces();
@ -256,10 +255,9 @@ exports.childShouldThrowAndAbort = function() {
 exports.ddCommand = function(filename, kilobytes) {
  if (exports.isWindows) {
    const p = path.resolve(exports.fixturesDir, 'create-file.js');
-    return '"' + process.argv[0] + '" "' + p + '" "' +
+    return `"${process.argv[0]}" "${p}" "${filename}" ${kilobytes * 1024}`;
           filename + '" ' + (kilobytes * 1024);
  } else {
-    return 'dd if=/dev/zero of="' + filename + '" bs=1024 count=' + kilobytes;
+    return `dd if=/dev/zero of="${filename}" bs=1024 count=${kilobytes}`;
  }
 };
@ -495,7 +493,7 @@ exports.canCreateSymLink = function() {
    let output = '';
    try {
-      output = execSync(whoamiPath + ' /priv', { timout: 1000 });
+      output = execSync(`${whoamiPath} /priv`, { timout: 1000 });
    } catch (e) {
      err = true;
    } finally {
@ -522,7 +520,7 @@ exports.skip = function(msg) {
 function ArrayStream() {
  this.run = function(data) {
    data.forEach((line) => {
-      this.emit('data', line + '\n');
+      this.emit('data', `${line}\n`);
    });
  };
 }
--- a/test/debugger/helper-debugger-repl.js
+++ b/test/debugger/helper-debugger-repl.js
@ -34,11 +34,11 @@ let quit;
 function startDebugger(scriptToDebug) {
  scriptToDebug = process.env.NODE_DEBUGGER_TEST_SCRIPT ||
-                  common.fixturesDir + '/' + scriptToDebug;
+                  `${common.fixturesDir}/${scriptToDebug}`;
-  child = spawn(process.execPath, ['debug', '--port=' + port, scriptToDebug]);
+  child = spawn(process.execPath, ['debug', `--port=${port}`, scriptToDebug]);
-  console.error('./node', 'debug', '--port=' + port, scriptToDebug);
+  console.error('./node', 'debug', `--port=${port}`, scriptToDebug);
  child.stdout.setEncoding('utf-8');
  child.stdout.on('data', function(data) {
@ -53,10 +53,10 @@ function startDebugger(scriptToDebug) {
  child.on('line', function(line) {
    line = line.replace(/^(debug> *)+/, '');
    console.log(line);
-    assert.ok(expected.length > 0, 'Got unexpected line: ' + line);
+    assert.ok(expected.length > 0, `Got unexpected line: ${line}`);
    const expectedLine = expected[0].lines.shift();
-    assert.ok(line.match(expectedLine) !== null, line + ' != ' + expectedLine);
+    assert.ok(line.match(expectedLine) !== null, `${line} != ${expectedLine}`);
    if (expected[0].lines.length === 0) {
      const callback = expected[0].callback;
@ -83,7 +83,7 @@ function startDebugger(scriptToDebug) {
    console.error('dying badly buffer=%j', buffer);
    let err = 'Timeout';
    if (expected.length > 0 && expected[0].lines) {
-      err = err + '. Expected: ' + expected[0].lines.shift();
+      err = `${err}. Expected: ${expected[0].lines.shift()}`;
    }
    child.on('close', function() {
@ -112,8 +112,8 @@ function startDebugger(scriptToDebug) {
 function addTest(input, output) {
  function next() {
    if (expected.length > 0) {
-      console.log('debug> ' + expected[0].input);
+      console.log(`debug> ${expected[0].input}`);
-      child.stdin.write(expected[0].input + '\n');
+      child.stdin.write(`${expected[0].input}\n`);
      if (!expected[0].lines) {
        const callback = expected[0].callback;
--- a/test/debugger/test-debugger-repl-utf8.js
+++ b/test/debugger/test-debugger-repl-utf8.js
@ -21,7 +21,7 @@
 'use strict';
 const common = require('../common');
-const script = common.fixturesDir + '/breakpoints_utf8.js';
+const script = `${common.fixturesDir}/breakpoints_utf8.js`;
 process.env.NODE_DEBUGGER_TEST_SCRIPT = script;
 require('./test-debugger-repl.js');
--- a/test/gc/test-http-client-connaborted.js
+++ b/test/gc/test-http-client-connaborted.js
@ -15,7 +15,7 @@ let done = 0;
 let count = 0;
 let countGC = 0;
-console.log('We should do ' + todo + ' requests');
+console.log(`We should do ${todo} requests`);
 const server = http.createServer(serverHandler);
 server.listen(0, getall);
--- a/test/gc/test-http-client-onerror.js
+++ b/test/gc/test-http-client-onerror.js
@ -17,7 +17,7 @@ let done = 0;
 let count = 0;
 let countGC = 0;
-console.log('We should do ' + todo + ' requests');
+console.log(`We should do ${todo} requests`);
 const server = http.createServer(serverHandler);
 server.listen(0, runTest);
--- a/test/gc/test-http-client-timeout.js
+++ b/test/gc/test-http-client-timeout.js
@ -19,7 +19,7 @@ let done = 0;
 let count = 0;
 let countGC = 0;
-console.log('We should do ' + todo + ' requests');
+console.log(`We should do ${todo} requests`);
 const server = http.createServer(serverHandler);
 server.listen(0, getall);
--- a/test/gc/test-http-client.js
+++ b/test/gc/test-http-client.js
@ -15,7 +15,7 @@ let done = 0;
 let count = 0;
 let countGC = 0;
-console.log('We should do ' + todo + ' requests');
+console.log(`We should do ${todo} requests`);
 const server = http.createServer(serverHandler);
 server.listen(0, getall);
--- a/test/gc/test-net-timeout.js
+++ b/test/gc/test-net-timeout.js
@ -26,7 +26,7 @@ let done = 0;
 let count = 0;
 let countGC = 0;
-console.log('We should do ' + todo + ' requests');
+console.log(`We should do ${todo} requests`);
 const server = net.createServer(serverHandler);
 server.listen(0, getall);
--- a/test/inspector/inspector-helper.js
+++ b/test/inspector/inspector-helper.js
@ -169,13 +169,15 @@ TestSession.prototype.processMessage_ = function(message) {
    assert.strictEqual(id, this.expectedId_);
    this.expectedId_++;
    if (this.responseCheckers_[id]) {
-      assert(message['result'], JSON.stringify(message) + ' (response to ' +
+      const messageJSON = JSON.stringify(message);
-             JSON.stringify(this.messages_[id]) + ')');
+      const idJSON = JSON.stringify(this.messages_[id]);
      assert(message['result'], `${messageJSON} (response to ${idJSON})`);
      this.responseCheckers_[id](message['result']);
      delete this.responseCheckers_[id];
    }
-    assert(!message['error'], JSON.stringify(message) + ' (replying to ' +
+    const messageJSON = JSON.stringify(message);
-           JSON.stringify(this.messages_[id]) + ')');
+    const idJSON = JSON.stringify(this.messages_[id]);
    assert(!message['error'], `${messageJSON} (replying to ${idJSON})`);
    delete this.messages_[id];
    if (id === this.lastId_) {
      this.lastMessageResponseCallback_ && this.lastMessageResponseCallback_();
@ -213,12 +215,8 @@ TestSession.prototype.sendInspectorCommands = function(commands) {
    };
    this.sendAll_(commands, () => {
      timeoutId = setTimeout(() => {
-        let s = '';
+        assert.fail(`Messages without response: ${
-        for (const id in this.messages_) {
+                    Object.keys(this.messages_).join(', ')}`);
          s += id + ', ';
        }
        assert.fail('Messages without response: ' +
                    s.substring(0, s.length - 2));
      }, TIMEOUT);
    });
  });
@ -241,7 +239,7 @@ TestSession.prototype.expectMessages = function(expects) {
  if (!(expects instanceof Array)) expects = [ expects ];
  const callback = this.createCallbackWithTimeout_(
-      'Matching response was not received:\n' + expects[0]);
+      `Matching response was not received:\n${expects[0]}`);
  this.messagefilter_ = (message) => {
    if (expects[0](message))
      expects.shift();
@ -256,7 +254,7 @@ TestSession.prototype.expectMessages = function(expects) {
 TestSession.prototype.expectStderrOutput = function(regexp) {
  this.harness_.addStderrFilter(
      regexp,
-      this.createCallbackWithTimeout_('Timed out waiting for ' + regexp));
+      this.createCallbackWithTimeout_(`Timed out waiting for ${regexp}`));
  return this;
 };
--- a/test/inspector/test-inspector.js
+++ b/test/inspector/test-inspector.js
@ -19,7 +19,7 @@ function checkVersion(err, response) {
  assert.ifError(err);
  assert.ok(response);
  const expected = {
-    'Browser': 'node.js/' + process.version,
+    'Browser': `node.js/${process.version}`,
    'Protocol-Version': '1.1',
  };
  assert.strictEqual(JSON.stringify(response),
@ -36,7 +36,7 @@ function expectMainScriptSource(result) {
  const expected = helper.mainScriptSource();
  const source = result['scriptSource'];
  assert(source && (source.includes(expected)),
-         'Script source is wrong: ' + source);
+         `Script source is wrong: ${source}`);
 }
 function setupExpectBreakOnLine(line, url, session, scopeIdCallback) {
@ -187,7 +187,7 @@ function testI18NCharacters(session) {
    {
      'method': 'Debugger.evaluateOnCallFrame', 'params': {
        'callFrameId': '{"ordinal":0,"injectedScriptId":1}',
-        'expression': 'console.log("' + chars + '")',
+        'expression': `console.log("${chars}")`,
        'objectGroup': 'console',
        'includeCommandLineAPI': true,
        'silent': false,
--- a/test/internet/test-dns-cares-domains.js
+++ b/test/internet/test-dns-cares-domains.js
@ -21,7 +21,7 @@ methods.forEach(function(method) {
  const d = domain.create();
  d.run(function() {
    dns[method]('google.com', function() {
-      assert.strictEqual(process.domain, d, method + ' retains domain');
+      assert.strictEqual(process.domain, d, `${method} retains domain`);
    });
  });
 });
--- a/test/internet/test-dns-ipv6.js
+++ b/test/internet/test-dns-ipv6.js
@ -164,7 +164,7 @@ TEST(function test_lookup_all_ipv6(done) {
      ips.forEach((ip) => {
        assert.ok(isIPv6(ip.address),
-                  'Invalid IPv6: ' + ip.address.toString());
+                  `Invalid IPv6: ${ip.address.toString()}`);
        assert.strictEqual(ip.family, 6);
      });
--- a/test/internet/test-dns.js
+++ b/test/internet/test-dns.js
@ -545,7 +545,7 @@ req.oncomplete = function(err, domains) {
 };
 process.on('exit', function() {
-  console.log(completed + ' tests completed');
+  console.log(`${completed} tests completed`);
  assert.strictEqual(running, false);
  assert.strictEqual(expected, completed);
  assert.ok(getaddrinfoCallbackCalled);
--- a/test/internet/test-tls-add-ca-cert.js
+++ b/test/internet/test-tls-add-ca-cert.js
@ -13,7 +13,7 @@ const fs = require('fs');
 const tls = require('tls');
 function filenamePEM(n) {
-  return require('path').join(common.fixturesDir, 'keys', n + '.pem');
+  return require('path').join(common.fixturesDir, 'keys', `${n}.pem`);
 }
 function loadPEM(n) {
--- a/test/known_issues/test-cwd-enoent-file.js
+++ b/test/known_issues/test-cwd-enoent-file.js
@ -19,7 +19,7 @@ if (process.argv[2] === 'child') {
  // Do nothing.
 } else {
  common.refreshTmpDir();
-  const dir = fs.mkdtempSync(common.tmpDir + '/');
+  const dir = fs.mkdtempSync(`${common.tmpDir}/`);
  process.chdir(dir);
  fs.rmdirSync(dir);
  assert.throws(process.cwd,
--- a/test/parallel/test-assert.js
+++ b/test/parallel/test-assert.js
@ -177,7 +177,7 @@ assert.doesNotThrow(makeBlock(a.deepEqual, a1, a2));
 // having an identical prototype property
 const nbRoot = {
-  toString: function() { return this.first + ' ' + this.last; }
+  toString: function() { return `${this.first} ${this.last}`; }
 };
 function nameBuilder(first, last) {
--- a/test/parallel/test-async-wrap-check-providers.js
+++ b/test/parallel/test-async-wrap-check-providers.js
@ -94,8 +94,8 @@ process.on('SIGINT', () => process.exit());
 // Run from closed net server above.
 function checkTLS() {
  const options = {
-    key: fs.readFileSync(common.fixturesDir + '/keys/ec-key.pem'),
+    key: fs.readFileSync(`${common.fixturesDir}/keys/ec-key.pem`),
-    cert: fs.readFileSync(common.fixturesDir + '/keys/ec-cert.pem')
+    cert: fs.readFileSync(`${common.fixturesDir}/keys/ec-cert.pem`)
  };
  const server = tls.createServer(options, common.noop)
    .listen(0, function() {
--- a/test/parallel/test-buffer-badhex.js
+++ b/test/parallel/test-buffer-badhex.js
@ -44,6 +44,6 @@ const Buffer = require('buffer').Buffer;
  const hex = buf.toString('hex');
  assert.deepStrictEqual(Buffer.from(hex, 'hex'), buf);
-  const badHex = hex.slice(0, 256) + 'xx' + hex.slice(256, 510);
+  const badHex = `${hex.slice(0, 256)}xx${hex.slice(256, 510)}`;
  assert.deepStrictEqual(Buffer.from(badHex, 'hex'), buf.slice(0, 128));
 }
--- a/test/parallel/test-buffer-includes.js
+++ b/test/parallel/test-buffer-includes.js
@ -199,7 +199,7 @@ const longBufferString = Buffer.from(longString);
 let pattern = 'ABACABADABACABA';
 for (let i = 0; i < longBufferString.length - pattern.length; i += 7) {
  const includes = longBufferString.includes(pattern, i);
-  assert(includes, 'Long ABACABA...-string at index ' + i);
+  assert(includes, `Long ABACABA...-string at index ${i}`);
 }
 assert(longBufferString.includes('AJABACA'), 'Long AJABACA, First J');
 assert(longBufferString.includes('AJABACA', 511), 'Long AJABACA, Second J');
--- a/test/parallel/test-buffer-indexof.js
+++ b/test/parallel/test-buffer-indexof.js
@ -255,7 +255,7 @@ let pattern = 'ABACABADABACABA';
 for (let i = 0; i < longBufferString.length - pattern.length; i += 7) {
  const index = longBufferString.indexOf(pattern, i);
  assert.strictEqual((i + 15) & ~0xf, index,
-                     'Long ABACABA...-string at index ' + i);
+                     `Long ABACABA...-string at index ${i}`);
 }
 assert.strictEqual(510, longBufferString.indexOf('AJABACA'),
                   'Long AJABACA, First J');
--- a/test/parallel/test-child-process-buffering.js
+++ b/test/parallel/test-child-process-buffering.js
@ -29,12 +29,12 @@ function pwd(callback) {
  child.stdout.setEncoding('utf8');
  child.stdout.on('data', function(s) {
-    console.log('stdout: ' + JSON.stringify(s));
+    console.log(`stdout: ${JSON.stringify(s)}`);
    output += s;
  });
  child.on('exit', common.mustCall(function(c) {
-    console.log('exit: ' + c);
+    console.log(`exit: ${c}`);
    assert.strictEqual(0, c);
  }));
--- a/test/parallel/test-child-process-default-options.js
+++ b/test/parallel/test-child-process-default-options.js
@ -39,7 +39,7 @@ let response = '';
 child.stdout.setEncoding('utf8');
 child.stdout.on('data', function(chunk) {
-  console.log('stdout: ' + chunk);
+  console.log(`stdout: ${chunk}`);
  response += chunk;
 });
--- a/test/parallel/test-child-process-double-pipe.js
+++ b/test/parallel/test-child-process-double-pipe.js
@ -56,7 +56,7 @@ if (common.isWindows) {
 // pipe echo | grep
 echo.stdout.on('data', function(data) {
-  console.error('grep stdin write ' + data.length);
+  console.error(`grep stdin write ${data.length}`);
  if (!grep.stdin.write(data)) {
    echo.stdout.pause();
  }
@ -86,7 +86,7 @@ sed.on('exit', function() {
 // pipe grep | sed
 grep.stdout.on('data', function(data) {
-  console.error('grep stdout ' + data.length);
+  console.error(`grep stdout ${data.length}`);
  if (!sed.stdin.write(data)) {
    grep.stdout.pause();
  }
--- a/test/parallel/test-child-process-env.js
+++ b/test/parallel/test-child-process-env.js
@ -45,7 +45,7 @@ let response = '';
 child.stdout.setEncoding('utf8');
 child.stdout.on('data', function(chunk) {
-  console.log('stdout: ' + chunk);
+  console.log(`stdout: ${chunk}`);
  response += chunk;
 });
--- a/test/parallel/test-child-process-exec-env.js
+++ b/test/parallel/test-child-process-exec-env.js
@ -31,9 +31,9 @@ let child;
 function after(err, stdout, stderr) {
  if (err) {
    error_count++;
-    console.log('error!: ' + err.code);
+    console.log(`error!: ${err.code}`);
-    console.log('stdout: ' + JSON.stringify(stdout));
+    console.log(`stdout: ${JSON.stringify(stdout)}`);
-    console.log('stderr: ' + JSON.stringify(stderr));
+    console.log(`stderr: ${JSON.stringify(stderr)}`);
    assert.strictEqual(false, err.killed);
  } else {
    success_count++;
--- a/test/parallel/test-child-process-fork-close.js
+++ b/test/parallel/test-child-process-fork-close.js
@ -24,7 +24,7 @@ const common = require('../common');
 const assert = require('assert');
 const fork = require('child_process').fork;
-const cp = fork(common.fixturesDir + '/child-process-message-and-exit.js');
+const cp = fork(`${common.fixturesDir}/child-process-message-and-exit.js`);
 let gotMessage = false;
 let gotExit = false;
--- a/test/parallel/test-child-process-fork.js
+++ b/test/parallel/test-child-process-fork.js
@ -25,7 +25,7 @@ const assert = require('assert');
 const fork = require('child_process').fork;
 const args = ['foo', 'bar'];
-const n = fork(common.fixturesDir + '/child-process-spawn-node.js', args);
+const n = fork(`${common.fixturesDir}/child-process-spawn-node.js`, args);
 assert.strictEqual(n.channel, n._channel);
 assert.deepStrictEqual(args, ['foo', 'bar']);
--- a/test/parallel/test-child-process-fork3.js
+++ b/test/parallel/test-child-process-fork3.js
@ -23,4 +23,4 @@
 const common = require('../common');
 const child_process = require('child_process');
-child_process.fork(common.fixturesDir + '/empty.js'); // should not hang
+child_process.fork(`${common.fixturesDir}/empty.js`); // should not hang
--- a/test/parallel/test-child-process-internal.js
+++ b/test/parallel/test-child-process-internal.js
@ -25,8 +25,8 @@ const assert = require('assert');
 //messages
 const PREFIX = 'NODE_';
-const normal = {cmd: 'foo' + PREFIX};
+const normal = {cmd: `foo${PREFIX}`};
-const internal = {cmd: PREFIX + 'bar'};
+const internal = {cmd: `${PREFIX}bar`};
 if (process.argv[2] === 'child') {
  //send non-internal message containing PREFIX at a non prefix position
--- a/test/parallel/test-child-process-ipc.js
+++ b/test/parallel/test-child-process-ipc.js
@ -36,13 +36,13 @@ let gotEcho = false;
 const child = spawn(process.argv[0], [sub]);
 child.stderr.on('data', function(data) {
-  console.log('parent stderr: ' + data);
+  console.log(`parent stderr: ${data}`);
 });
 child.stdout.setEncoding('utf8');
 child.stdout.on('data', function(data) {
-  console.log('child said: ' + JSON.stringify(data));
+  console.log(`child said: ${JSON.stringify(data)}`);
  if (!gotHelloWorld) {
    console.error('testing for hello world');
    assert.strictEqual('hello world\r\n', data);
--- a/test/parallel/test-child-process-set-blocking.js
+++ b/test/parallel/test-child-process-set-blocking.js
@ -26,7 +26,7 @@ const ch = require('child_process');
 const SIZE = 100000;
-const cp = ch.spawn('python', ['-c', 'print ' + SIZE + ' * "C"'], {
+const cp = ch.spawn('python', ['-c', `print ${SIZE} * "C"`], {
  stdio: 'inherit'
 });
--- a/test/parallel/test-child-process-spawn-error.js
+++ b/test/parallel/test-child-process-spawn-error.js
@ -32,7 +32,7 @@ const enoentChild = spawn(enoentPath, spawnargs);
 enoentChild.on('error', common.mustCall(function(err) {
  assert.strictEqual(err.code, 'ENOENT');
  assert.strictEqual(err.errno, 'ENOENT');
-  assert.strictEqual(err.syscall, 'spawn ' + enoentPath);
+  assert.strictEqual(err.syscall, `spawn ${enoentPath}`);
  assert.strictEqual(err.path, enoentPath);
  assert.deepStrictEqual(err.spawnargs, spawnargs);
 }));
--- a/test/parallel/test-child-process-spawn-typeerror.js
+++ b/test/parallel/test-child-process-spawn-typeerror.js
@ -32,7 +32,7 @@ const invalidArgsMsg = /Incorrect value of args option/;
 const invalidOptionsMsg = /"options" argument must be an object/;
 const invalidFileMsg =
  /^TypeError: "file" argument must be a non-empty string$/;
-const empty = common.fixturesDir + '/empty.js';
+const empty = `${common.fixturesDir}/empty.js`;
 assert.throws(function() {
  const child = spawn(invalidcmd, 'this is not an array');
--- a/test/parallel/test-child-process-spawnsync-input.js
+++ b/test/parallel/test-child-process-spawnsync-input.js
@ -30,8 +30,8 @@ const msgOut = 'this is stdout';
 const msgErr = 'this is stderr';
 // this is actually not os.EOL?
-const msgOutBuf = Buffer.from(msgOut + '\n');
+const msgOutBuf = Buffer.from(`${msgOut}\n`);
-const msgErrBuf = Buffer.from(msgErr + '\n');
+const msgErrBuf = Buffer.from(`${msgErr}\n`);
 const args = [
  '-e',
@ -117,5 +117,5 @@ verifyBufOutput(spawnSync(process.execPath, args));
 ret = spawnSync(process.execPath, args, { encoding: 'utf8' });
 checkSpawnSyncRet(ret);
-assert.strictEqual(ret.stdout, msgOut + '\n');
+assert.strictEqual(ret.stdout, `${msgOut}\n`);
-assert.strictEqual(ret.stderr, msgErr + '\n');
+assert.strictEqual(ret.stderr, `${msgErr}\n`);
--- a/test/parallel/test-child-process-spawnsync-maxbuf.js
+++ b/test/parallel/test-child-process-spawnsync-maxbuf.js
@ -5,7 +5,7 @@ const spawnSync = require('child_process').spawnSync;
 const msgOut = 'this is stdout';
 // This is actually not os.EOL?
-const msgOutBuf = Buffer.from(msgOut + '\n');
+const msgOutBuf = Buffer.from(`${msgOut}\n`);
 const args = [
  '-e',
--- a/test/parallel/test-child-process-stdin.js
+++ b/test/parallel/test-child-process-stdin.js
@ -39,7 +39,7 @@ let response = '';
 cat.stdout.setEncoding('utf8');
 cat.stdout.on('data', function(chunk) {
-  console.log('stdout: ' + chunk);
+  console.log(`stdout: ${chunk}`);
  response += chunk;
 });
--- a/test/parallel/test-cli-eval.js
+++ b/test/parallel/test-cli-eval.js
@ -203,7 +203,7 @@ child.exec(`${nodejs} --use-strict -p process.execArgv`,
  const opt = ' --eval "console.log(process.argv.slice(1).join(\' \'))"';
  const cmd = `${nodejs}${opt} -- ${args}`;
  child.exec(cmd, common.mustCall(function(err, stdout, stderr) {
-    assert.strictEqual(stdout, args + '\n');
+    assert.strictEqual(stdout, `${args}\n`);
    assert.strictEqual(stderr, '');
    assert.strictEqual(err, null);
  }));
@ -212,7 +212,7 @@ child.exec(`${nodejs} --use-strict -p process.execArgv`,
  const popt = ' --print "process.argv.slice(1).join(\' \')"';
  const pcmd = `${nodejs}${popt} -- ${args}`;
  child.exec(pcmd, common.mustCall(function(err, stdout, stderr) {
-    assert.strictEqual(stdout, args + '\n');
+    assert.strictEqual(stdout, `${args}\n`);
    assert.strictEqual(stderr, '');
    assert.strictEqual(err, null);
  }));
@ -222,7 +222,7 @@ child.exec(`${nodejs} --use-strict -p process.execArgv`,
  // filename.
  const filecmd = `${nodejs} -- ${__filename} ${args}`;
  child.exec(filecmd, common.mustCall(function(err, stdout, stderr) {
-    assert.strictEqual(stdout, args + '\n');
+    assert.strictEqual(stdout, `${args}\n`);
    assert.strictEqual(stderr, '');
    assert.strictEqual(err, null);
  }));
--- a/test/parallel/test-cli-node-options.js
+++ b/test/parallel/test-cli-node-options.js
@ -31,8 +31,7 @@ function disallow(opt) {
  const options = {env: {NODE_OPTIONS: opt}};
  exec(process.execPath, options, common.mustCall(function(err) {
    const message = err.message.split(/\r?\n/)[1];
-    const expect = process.execPath + ': ' + opt +
+    const expect = `${process.execPath}: ${opt} is not allowed in NODE_OPTIONS`;
                   ' is not allowed in NODE_OPTIONS';
    assert.strictEqual(err.code, 9);
    assert.strictEqual(message, expect);
@ -41,7 +40,7 @@ function disallow(opt) {
 const printA = require.resolve('../fixtures/printA.js');
-expect('-r ' + printA, 'A\nB\n');
+expect(`-r ${printA}`, 'A\nB\n');
 expect('--no-deprecation', 'B\n');
 expect('--no-warnings', 'B\n');
 expect('--trace-warnings', 'B\n');
@ -75,7 +74,7 @@ function expect(opt, want) {
    if (!RegExp(want).test(stdout)) {
      console.error('For %j, failed to find %j in: <\n%s\n>',
                    opt, expect, stdout);
-      assert(false, 'Expected ' + expect);
+      assert(false, `Expected ${expect}`);
    }
  }));
 }
--- a/test/parallel/test-cli-syntax.js
+++ b/test/parallel/test-cli-syntax.js
@ -31,7 +31,7 @@ const syntaxArgs = [
    // no output should be produced
    assert.strictEqual(c.stdout, '', 'stdout produced');
    assert.strictEqual(c.stderr, '', 'stderr produced');
-    assert.strictEqual(c.status, 0, 'code === ' + c.status);
+    assert.strictEqual(c.status, 0, `code === ${c.status}`);
  });
 });
@ -59,7 +59,7 @@ const syntaxArgs = [
    const match = c.stderr.match(/^SyntaxError: Unexpected identifier$/m);
    assert(match, 'stderr incorrect');
-    assert.strictEqual(c.status, 1, 'code === ' + c.status);
+    assert.strictEqual(c.status, 1, `code === ${c.status}`);
  });
 });
@ -82,7 +82,7 @@ const syntaxArgs = [
    const match = c.stderr.match(/^Error: Cannot find module/m);
    assert(match, 'stderr incorrect');
-    assert.strictEqual(c.status, 1, 'code === ' + c.status);
+    assert.strictEqual(c.status, 1, `code === ${c.status}`);
  });
 });
@ -96,7 +96,7 @@ syntaxArgs.forEach(function(args) {
  assert.strictEqual(c.stdout, '', 'stdout produced');
  assert.strictEqual(c.stderr, '', 'stderr produced');
-  assert.strictEqual(c.status, 0, 'code === ' + c.status);
+  assert.strictEqual(c.status, 0, `code === ${c.status}`);
 });
 // should throw if code piped from stdin with --check has bad syntax
@ -115,7 +115,7 @@ syntaxArgs.forEach(function(args) {
  const match = c.stderr.match(/^SyntaxError: Unexpected identifier$/m);
  assert(match, 'stderr incorrect');
-  assert.strictEqual(c.status, 1, 'code === ' + c.status);
+  assert.strictEqual(c.status, 1, `code === ${c.status}`);
 });
 // should throw if -c and -e flags are both passed
@ -130,6 +130,6 @@ syntaxArgs.forEach(function(args) {
      )
    );
-    assert.strictEqual(c.status, 9, 'code === ' + c.status);
+    assert.strictEqual(c.status, 9, `code === ${c.status}`);
  });
 });
--- a/test/parallel/test-cluster-bind-twice.js
+++ b/test/parallel/test-cluster-bind-twice.js
@ -54,14 +54,14 @@ if (!id) {
  a.on('exit', common.mustCall((c) => {
    if (c) {
      b.send('QUIT');
-      throw new Error('A exited with ' + c);
+      throw new Error(`A exited with ${c}`);
    }
  }));
  b.on('exit', common.mustCall((c) => {
    if (c) {
      a.send('QUIT');
-      throw new Error('B exited with ' + c);
+      throw new Error(`B exited with ${c}`);
    }
  }));
--- a/test/parallel/test-cluster-eaccess.js
+++ b/test/parallel/test-cluster-eaccess.js
@ -58,7 +58,7 @@ if (cluster.isMaster) {
 } else {
  common.refreshTmpDir();
-  const cp = fork(common.fixturesDir + '/listen-on-socket-and-exit.js',
+  const cp = fork(`${common.fixturesDir}/listen-on-socket-and-exit.js`,
                { stdio: 'inherit' });
  // message from the child indicates it's ready and listening
--- a/test/parallel/test-cluster-eaddrinuse.js
+++ b/test/parallel/test-cluster-eaddrinuse.js
@ -29,8 +29,8 @@ const assert = require('assert');
 const fork = require('child_process').fork;
 const net = require('net');
-const id = '' + process.argv[2];
+const id = String(process.argv[2]);
-const port = '' + process.argv[3];
+const port = String(process.argv[3]);
 if (id === 'undefined') {
  const server = net.createServer(common.mustNotCall());
--- a/test/parallel/test-cluster-message.js
+++ b/test/parallel/test-cluster-message.js
@ -123,7 +123,7 @@ if (cluster.isWorker) {
      if (data.code === 'received message') {
        check('worker', data.echo === 'message from master');
      } else {
-        throw new Error('wrong TCP message received: ' + data);
+        throw new Error(`wrong TCP message received: ${data}`);
      }
    });
@ -139,9 +139,8 @@ if (cluster.isWorker) {
  process.once('exit', function() {
    forEach(checks, function(check, type) {
-      assert.ok(check.receive, 'The ' + type + ' did not receive any message');
+      assert.ok(check.receive, `The ${type} did not receive any message`);
-      assert.ok(check.correct,
+      assert.ok(check.correct, `The ${type} did not get the correct message`);
                'The ' + type + ' did not get the correct message');
    });
  });
 }
--- a/test/parallel/test-cluster-worker-exit.js
+++ b/test/parallel/test-cluster-worker-exit.js
@ -125,9 +125,8 @@ function checkResults(expected_results, results) {
    const actual = results[k];
    const expected = expected_results[k];
-    assert.strictEqual(actual,
+    assert.strictEqual(
-                       expected && expected.length ? expected[0] : expected,
+      actual, expected && expected.length ? expected[0] : expected,
-                       (expected[1] || '') +
+      `${expected[1] || ''} [expected: ${expected[0]} / actual: ${actual}]`);
                         ` [expected: ${expected[0]} / actual: ${actual}]`);
  }
 }
--- a/test/parallel/test-cluster-worker-kill.js
+++ b/test/parallel/test-cluster-worker-kill.js
@ -111,9 +111,8 @@ function checkResults(expected_results, results) {
    const actual = results[k];
    const expected = expected_results[k];
-    assert.strictEqual(actual,
+    assert.strictEqual(
-                       expected && expected.length ? expected[0] : expected,
+      actual, expected && expected.length ? expected[0] : expected,
-                       (expected[1] || '') +
+      `${expected[1] || ''} [expected: ${expected[0]} / actual: ${actual}]`);
                         ` [expected: ${expected[0]} / actual: ${actual}]`);
  }
 }
--- a/test/parallel/test-console.js
+++ b/test/parallel/test-console.js
@ -123,13 +123,13 @@ const expectedStrings = [
 ];
 for (const expected of expectedStrings) {
-  assert.strictEqual(expected + '\n', strings.shift());
+  assert.strictEqual(`${expected}\n`, strings.shift());
-  assert.strictEqual(expected + '\n', errStrings.shift());
+  assert.strictEqual(`${expected}\n`, errStrings.shift());
 }
 for (const expected of expectedStrings) {
-  assert.strictEqual(expected + '\n', strings.shift());
+  assert.strictEqual(`${expected}\n`, strings.shift());
-  assert.strictEqual(expected + '\n', errStrings.shift());
+  assert.strictEqual(`${expected}\n`, errStrings.shift());
 }
 assert.strictEqual("{ foo: 'bar', inspect: [Function: inspect] }\n",
--- a/test/parallel/test-crypto-authenticated.js
+++ b/test/parallel/test-crypto-authenticated.js
@ -334,7 +334,7 @@ for (const i in TEST_CASES) {
  const test = TEST_CASES[i];
  if (!ciphers.includes(test.algo)) {
-    common.skip('unsupported ' + test.algo + ' test');
+    common.skip(`unsupported ${test.algo} test`);
    continue;
  }
--- a/test/parallel/test-crypto-binary-default.js
+++ b/test/parallel/test-crypto-binary-default.js
@ -37,17 +37,16 @@ const fs = require('fs');
 const path = require('path');
 const tls = require('tls');
 const DH_NOT_SUITABLE_GENERATOR = crypto.constants.DH_NOT_SUITABLE_GENERATOR;
 const fixtDir = common.fixturesDir;
 crypto.DEFAULT_ENCODING = 'latin1';
 // Test Certificates
-const certPem = fs.readFileSync(common.fixturesDir + '/test_cert.pem', 'ascii');
+const certPem = fs.readFileSync(`${fixtDir}/test_cert.pem`, 'ascii');
-const certPfx = fs.readFileSync(common.fixturesDir + '/test_cert.pfx');
+const certPfx = fs.readFileSync(`${fixtDir}/test_cert.pfx`);
-const keyPem = fs.readFileSync(common.fixturesDir + '/test_key.pem', 'ascii');
+const keyPem = fs.readFileSync(`${fixtDir}/test_key.pem`, 'ascii');
-const rsaPubPem = fs.readFileSync(common.fixturesDir + '/test_rsa_pubkey.pem',
+const rsaPubPem = fs.readFileSync(`${fixtDir}/test_rsa_pubkey.pem`, 'ascii');
-                                  'ascii');
+const rsaKeyPem = fs.readFileSync(`${fixtDir}/test_rsa_privkey.pem`, 'ascii');
 const rsaKeyPem = fs.readFileSync(common.fixturesDir + '/test_rsa_privkey.pem',
                                  'ascii');
 // PFX tests
 assert.doesNotThrow(function() {
@ -408,7 +407,7 @@ const h2 = crypto.createHash('sha1').update('Test').update('123').digest('hex');
 assert.strictEqual(h1, h2, 'multipled updates');
 // Test hashing for binary files
-const fn = path.join(common.fixturesDir, 'sample.png');
+const fn = path.join(fixtDir, 'sample.png');
 const sha1Hash = crypto.createHash('sha1');
 const fileStream = fs.createReadStream(fn);
 fileStream.on('data', function(data) {
@ -617,11 +616,9 @@ assert.strictEqual(rsaVerify.verify(rsaPubPem, rsaSignature, 'hex'), true);
 // Test RSA signing and verification
 //
 {
-  const privateKey = fs.readFileSync(
+  const privateKey = fs.readFileSync(`${fixtDir}/test_rsa_privkey_2.pem`);
      common.fixturesDir + '/test_rsa_privkey_2.pem');
-  const publicKey = fs.readFileSync(
+  const publicKey = fs.readFileSync(`${fixtDir}/test_rsa_pubkey_2.pem`);
      common.fixturesDir + '/test_rsa_pubkey_2.pem');
  const input = 'I AM THE WALRUS';
@ -649,11 +646,9 @@ assert.strictEqual(rsaVerify.verify(rsaPubPem, rsaSignature, 'hex'), true);
 // Test DSA signing and verification
 //
 {
-  const privateKey = fs.readFileSync(
+  const privateKey = fs.readFileSync(`${fixtDir}/test_dsa_privkey.pem`);
      common.fixturesDir + '/test_dsa_privkey.pem');
-  const publicKey = fs.readFileSync(
+  const publicKey = fs.readFileSync(`${fixtDir}/test_dsa_pubkey.pem`);
      common.fixturesDir + '/test_dsa_pubkey.pem');
  const input = 'I AM THE WALRUS';
--- a/test/parallel/test-crypto-certificate.js
+++ b/test/parallel/test-crypto-certificate.js
@ -34,9 +34,9 @@ crypto.DEFAULT_ENCODING = 'buffer';
 const fs = require('fs');
 // Test Certificates
-const spkacValid = fs.readFileSync(common.fixturesDir + '/spkac.valid');
+const spkacValid = fs.readFileSync(`${common.fixturesDir}/spkac.valid`);
-const spkacFail = fs.readFileSync(common.fixturesDir + '/spkac.fail');
+const spkacFail = fs.readFileSync(`${common.fixturesDir}/spkac.fail`);
-const spkacPem = fs.readFileSync(common.fixturesDir + '/spkac.pem');
+const spkacPem = fs.readFileSync(`${common.fixturesDir}/spkac.pem`);
 const certificate = new crypto.Certificate();
--- a/test/parallel/test-crypto-fips.js
+++ b/test/parallel/test-crypto-fips.js
@ -31,19 +31,18 @@ function addToEnv(newVar, value) {
 }
 function testHelper(stream, args, expectedOutput, cmd, env) {
-  const fullArgs = args.concat(['-e', 'console.log(' + cmd + ')']);
+  const fullArgs = args.concat(['-e', `console.log(${cmd})`]);
  const child = spawnSync(process.execPath, fullArgs, {
    cwd: path.dirname(process.execPath),
    env: env
  });
-  console.error('Spawned child [pid:' + child.pid + '] with cmd \'' +
+  console.error(
-      cmd + '\' expect %j with args \'' + args + '\'' +
+    `Spawned child [pid:${child.pid}] with cmd '${cmd}' expect %j with args '${
-      ' OPENSSL_CONF=%j', expectedOutput, env.OPENSSL_CONF);
+    args}' OPENSSL_CONF=%j`, expectedOutput, env.OPENSSL_CONF);
  function childOk(child) {
-    console.error('Child #' + ++num_children_ok +
+    console.error(`Child #${++num_children_ok} [pid:${child.pid}] OK.`);
        ' [pid:' + child.pid + '] OK.');
  }
  function responseHandler(buffer, expectedOutput) {
--- a/test/parallel/test-crypto-rsa-dsa.js
+++ b/test/parallel/test-crypto-rsa-dsa.js
@ -10,21 +10,19 @@ if (!common.hasCrypto) {
 const constants = require('crypto').constants;
 const crypto = require('crypto');
 const fixtDir = common.fixturesDir;
 // Test certificates
-const certPem = fs.readFileSync(common.fixturesDir + '/test_cert.pem', 'ascii');
+const certPem = fs.readFileSync(`${fixtDir}/test_cert.pem`, 'ascii');
-const keyPem = fs.readFileSync(common.fixturesDir + '/test_key.pem', 'ascii');
+const keyPem = fs.readFileSync(`${fixtDir}/test_key.pem`, 'ascii');
-const rsaPubPem = fs.readFileSync(common.fixturesDir + '/test_rsa_pubkey.pem',
+const rsaPubPem = fs.readFileSync(`${fixtDir}/test_rsa_pubkey.pem`, 'ascii');
-                                  'ascii');
+const rsaKeyPem = fs.readFileSync(`${fixtDir}/test_rsa_privkey.pem`, 'ascii');
 const rsaKeyPem = fs.readFileSync(common.fixturesDir + '/test_rsa_privkey.pem',
                                  'ascii');
 const rsaKeyPemEncrypted = fs.readFileSync(
-  common.fixturesDir + '/test_rsa_privkey_encrypted.pem', 'ascii');
+  `${fixtDir}/test_rsa_privkey_encrypted.pem`, 'ascii');
-const dsaPubPem = fs.readFileSync(common.fixturesDir + '/test_dsa_pubkey.pem',
+const dsaPubPem = fs.readFileSync(`${fixtDir}/test_dsa_pubkey.pem`, 'ascii');
-                                  'ascii');
+const dsaKeyPem = fs.readFileSync(`${fixtDir}/test_dsa_privkey.pem`, 'ascii');
 const dsaKeyPem = fs.readFileSync(common.fixturesDir + '/test_dsa_privkey.pem',
                                  'ascii');
 const dsaKeyPemEncrypted = fs.readFileSync(
-  common.fixturesDir + '/test_dsa_privkey_encrypted.pem', 'ascii');
+  `${fixtDir}/test_dsa_privkey_encrypted.pem`, 'ascii');
 const decryptError =
  /^Error: error:06065064:digital envelope routines:EVP_DecryptFinal_ex:bad decrypt$/;
@ -178,11 +176,9 @@ assert.throws(() => {
 // Test RSA signing and verification
 //
 {
-  const privateKey = fs.readFileSync(
+  const privateKey = fs.readFileSync(`${fixtDir}/test_rsa_privkey_2.pem`);
      common.fixturesDir + '/test_rsa_privkey_2.pem');
-  const publicKey = fs.readFileSync(
+  const publicKey = fs.readFileSync(`${fixtDir}/test_rsa_pubkey_2.pem`);
      common.fixturesDir + '/test_rsa_pubkey_2.pem');
  const input = 'I AM THE WALRUS';
--- a/test/parallel/test-crypto-sign-verify.js
+++ b/test/parallel/test-crypto-sign-verify.js
@ -12,8 +12,8 @@ if (!common.hasCrypto) {
 const crypto = require('crypto');
 // Test certificates
-const certPem = fs.readFileSync(common.fixturesDir + '/test_cert.pem', 'ascii');
+const certPem = fs.readFileSync(`${common.fixturesDir}/test_cert.pem`, 'ascii');
-const keyPem = fs.readFileSync(common.fixturesDir + '/test_key.pem', 'ascii');
+const keyPem = fs.readFileSync(`${common.fixturesDir}/test_key.pem`, 'ascii');
 const modSize = 1024;
 // Test signing and verifying
@ -265,10 +265,10 @@ const modSize = 1024;
  const msgfile = path.join(common.tmpDir, 's5.msg');
  fs.writeFileSync(msgfile, msg);
-  const cmd = '"' + common.opensslCli + '" dgst -sha256 -verify "' + pubfile +
+  const cmd =
-              '" -signature "' + sigfile +
+    `"${common.opensslCli}" dgst -sha256 -verify "${pubfile}" -signature "${
-              '" -sigopt rsa_padding_mode:pss -sigopt rsa_pss_saltlen:-2 "' +
+    sigfile}" -sigopt rsa_padding_mode:pss -sigopt rsa_pss_saltlen:-2 "${
-              msgfile + '"';
+    msgfile}"`;
  exec(cmd, common.mustCall((err, stdout, stderr) => {
    assert(stdout.includes('Verified OK'));
--- a/test/parallel/test-crypto-verify-failure.js
+++ b/test/parallel/test-crypto-verify-failure.js
@ -33,11 +33,11 @@ crypto.DEFAULT_ENCODING = 'buffer';
 const fs = require('fs');
-const certPem = fs.readFileSync(common.fixturesDir + '/test_cert.pem', 'ascii');
+const certPem = fs.readFileSync(`${common.fixturesDir}/test_cert.pem`, 'ascii');
 const options = {
-  key: fs.readFileSync(common.fixturesDir + '/keys/agent1-key.pem'),
+  key: fs.readFileSync(`${common.fixturesDir}/keys/agent1-key.pem`),
-  cert: fs.readFileSync(common.fixturesDir + '/keys/agent1-cert.pem')
+  cert: fs.readFileSync(`${common.fixturesDir}/keys/agent1-cert.pem`)
 };
 const server = tls.Server(options, (socket) => {
--- a/test/parallel/test-crypto.js
+++ b/test/parallel/test-crypto.js
@ -35,10 +35,10 @@ const tls = require('tls');
 crypto.DEFAULT_ENCODING = 'buffer';
 // Test Certificates
-const caPem = fs.readFileSync(common.fixturesDir + '/test_ca.pem', 'ascii');
+const caPem = fs.readFileSync(`${common.fixturesDir}/test_ca.pem`, 'ascii');
-const certPem = fs.readFileSync(common.fixturesDir + '/test_cert.pem', 'ascii');
+const certPem = fs.readFileSync(`${common.fixturesDir}/test_cert.pem`, 'ascii');
-const certPfx = fs.readFileSync(common.fixturesDir + '/test_cert.pfx');
+const certPfx = fs.readFileSync(`${common.fixturesDir}/test_cert.pfx`);
-const keyPem = fs.readFileSync(common.fixturesDir + '/test_key.pem', 'ascii');
+const keyPem = fs.readFileSync(`${common.fixturesDir}/test_key.pem`, 'ascii');
 // 'this' safety
 // https://github.com/joyent/node/issues/6690
@ -177,8 +177,8 @@ assert.throws(function() {
  //   $ openssl pkcs8 -topk8 -inform PEM -outform PEM -in mykey.pem \
  //     -out private_key.pem -nocrypt;
  //   Then open private_key.pem and change its header and footer.
-  const sha1_privateKey = fs.readFileSync(common.fixturesDir +
+  const sha1_privateKey = fs.readFileSync(
-                                        '/test_bad_rsa_privkey.pem', 'ascii');
+    `${common.fixturesDir}/test_bad_rsa_privkey.pem`, 'ascii');
  // this would inject errors onto OpenSSL's error stack
  crypto.createSign('sha1').sign(sha1_privateKey);
 }, /asn1 encoding routines:ASN1_CHECK_TLEN:wrong tag/);
--- a/test/parallel/test-cwd-enoent-preload.js
+++ b/test/parallel/test-cwd-enoent-preload.js
@ -10,7 +10,7 @@ if (common.isSunOS || common.isWindows || common.isAix) {
  return;
 }
-const dirname = common.tmpDir + '/cwd-does-not-exist-' + process.pid;
+const dirname = `${common.tmpDir}/cwd-does-not-exist-${process.pid}`;
 const abspathFile = require('path').join(common.fixturesDir, 'a.js');
 common.refreshTmpDir();
 fs.mkdirSync(dirname);
--- a/test/parallel/test-cwd-enoent-repl.js
+++ b/test/parallel/test-cwd-enoent-repl.js
@ -10,7 +10,7 @@ if (common.isSunOS || common.isWindows || common.isAix) {
  return;
 }
-const dirname = common.tmpDir + '/cwd-does-not-exist-' + process.pid;
+const dirname = `${common.tmpDir}/cwd-does-not-exist-${process.pid}`;
 common.refreshTmpDir();
 fs.mkdirSync(dirname);
 process.chdir(dirname);
--- a/test/parallel/test-cwd-enoent.js
+++ b/test/parallel/test-cwd-enoent.js
@ -10,7 +10,7 @@ if (common.isSunOS || common.isWindows || common.isAix) {
  return;
 }
-const dirname = common.tmpDir + '/cwd-does-not-exist-' + process.pid;
+const dirname = `${common.tmpDir}/cwd-does-not-exist-${process.pid}`;
 common.refreshTmpDir();
 fs.mkdirSync(dirname);
 process.chdir(dirname);
--- a/test/parallel/test-dgram-bind-shared-ports.js
+++ b/test/parallel/test-dgram-bind-shared-ports.js
@ -54,12 +54,12 @@ if (cluster.isMaster) {
  socket1.on('error', (err) => {
    // no errors expected
-    process.send('socket1:' + err.code);
+    process.send(`socket1:${err.code}`);
  });
  socket2.on('error', (err) => {
    // an error is expected on the second worker
-    process.send('socket2:' + err.code);
+    process.send(`socket2:${err.code}`);
  });
  socket1.bind({
--- a/test/parallel/test-dgram-error-message-address.js
+++ b/test/parallel/test-dgram-error-message-address.js
@ -49,7 +49,7 @@ socket_ipv6.on('error', common.mustCall(function(e) {
  const allowed = ['EADDRNOTAVAIL', 'EAFNOSUPPORT', 'EPROTONOSUPPORT'];
  assert.notStrictEqual(allowed.indexOf(e.code), -1);
  assert.strictEqual(e.port, undefined);
-  assert.strictEqual(e.message, 'bind ' + e.code + ' 111::1');
+  assert.strictEqual(e.message, `bind ${e.code} 111::1`);
  assert.strictEqual(e.address, '111::1');
  socket_ipv6.close();
 }));
--- a/test/parallel/test-domain-enter-exit.js
+++ b/test/parallel/test-domain-enter-exit.js
@ -41,20 +41,20 @@ c.name = 'c';
 a.enter(); // push
 assert.deepStrictEqual(domain._stack, [a],
-                       'a not pushed: ' + names(domain._stack));
+                       `a not pushed: ${names(domain._stack)}`);
 b.enter(); // push
 assert.deepStrictEqual(domain._stack, [a, b],
-                       'b not pushed: ' + names(domain._stack));
+                       `b not pushed: ${names(domain._stack)}`);
 c.enter(); // push
 assert.deepStrictEqual(domain._stack, [a, b, c],
-                       'c not pushed: ' + names(domain._stack));
+                       `c not pushed: ${names(domain._stack)}`);
 b.exit(); // pop
 assert.deepStrictEqual(domain._stack, [a],
-                       'b and c not popped: ' + names(domain._stack));
+                       `b and c not popped: ${names(domain._stack)}`);
 b.enter(); // push
 assert.deepStrictEqual(domain._stack, [a, b],
-                       'b not pushed: ' + names(domain._stack));
+                       `b not pushed: ${names(domain._stack)}`);
--- a/test/parallel/test-domain-uncaught-exception.js
+++ b/test/parallel/test-domain-uncaught-exception.js
@ -184,16 +184,15 @@ if (process.argv[2] === 'child') {
      test.expectedMessages.forEach(function(expectedMessage) {
        if (test.messagesReceived === undefined ||
          test.messagesReceived.indexOf(expectedMessage) === -1)
-          assert.fail('test ' + test.fn.name + ' should have sent message: ' +
+          assert.fail(`test ${test.fn.name} should have sent message: ${
-                      expectedMessage + ' but didn\'t');
+                      expectedMessage} but didn't`);
      });
      if (test.messagesReceived) {
        test.messagesReceived.forEach(function(receivedMessage) {
          if (test.expectedMessages.indexOf(receivedMessage) === -1) {
-            assert.fail('test ' + test.fn.name +
+            assert.fail(`test ${test.fn.name} should not have sent message: ${
-                        ' should not have sent message: ' + receivedMessage +
+                        receivedMessage} but did`);
                        ' but did');
          }
        });
      }
--- a/test/parallel/test-domain-with-abort-on-uncaught-exception.js
+++ b/test/parallel/test-domain-with-abort-on-uncaught-exception.js
@ -103,14 +103,8 @@ if (process.argv[2] === 'child') {
    if (options.useTryCatch)
      useTryCatchOpt = 'useTryCatch';
-    cmdToExec += process.argv[0] + ' ';
+    cmdToExec += `${process.argv[0]} ${cmdLineOption ? cmdLineOption : ''} ${
-    cmdToExec += (cmdLineOption ? cmdLineOption : '') + ' ';
+      process.argv[1]} child ${throwInDomainErrHandlerOpt} ${useTryCatchOpt}`;
    cmdToExec += process.argv[1] + ' ';
    cmdToExec += [
      'child',
      throwInDomainErrHandlerOpt,
      useTryCatchOpt
    ].join(' ');
    const child = exec(cmdToExec);
--- a/test/parallel/test-domain.js
+++ b/test/parallel/test-domain.js
@ -251,9 +251,7 @@ assert.strictEqual(result, 'return value');
 // check if the executed function take in count the applied parameters
-result = d.run(function(a, b) {
+result = d.run((a, b) => `${a} ${b}`, 'return', 'value');
  return a + ' ' + b;
 }, 'return', 'value');
 assert.strictEqual(result, 'return value');
--- a/test/parallel/test-dsa-fips-invalid-key.js
+++ b/test/parallel/test-dsa-fips-invalid-key.js
@ -12,8 +12,8 @@ const fs = require('fs');
 const input = 'hello';
-const dsapri = fs.readFileSync(common.fixturesDir +
+const dsapri = fs.readFileSync(
-                             '/keys/dsa_private_1025.pem');
+  `${common.fixturesDir}/keys/dsa_private_1025.pem`);
 const sign = crypto.createSign('DSS1');
 sign.update(input);
--- a/test/parallel/test-error-reporting.js
+++ b/test/parallel/test-error-reporting.js
@ -26,8 +26,7 @@ const exec = require('child_process').exec;
 const path = require('path');
 function errExec(script, callback) {
-  const cmd = '"' + process.argv[0] + '" "' +
+  const cmd = `"${process.argv[0]}" "${path.join(common.fixturesDir, script)}"`;
              path.join(common.fixturesDir, script) + '"';
  return exec(cmd, function(err, stdout, stderr) {
    // There was some error
    assert.ok(err);
--- a/test/parallel/test-eval.js
+++ b/test/parallel/test-eval.js
@ -29,7 +29,7 @@ const cmd = [
  `"${process.execPath}"`, '-e',
  '"console.error(process.argv)"',
  'foo', 'bar'].join(' ');
-const expected = util.format([process.execPath, 'foo', 'bar']) + '\n';
+const expected = `${util.format([process.execPath, 'foo', 'bar'])}\n`;
 exec(cmd, common.mustCall((err, stdout, stderr) => {
  assert.ifError(err);
  assert.strictEqual(stderr, expected);
--- a/test/parallel/test-exception-handler2.js
+++ b/test/parallel/test-exception-handler2.js
@ -24,7 +24,7 @@ const common = require('../common');
 const assert = require('assert');
 process.on('uncaughtException', function(err) {
-  console.log('Caught exception: ' + err);
+  console.log(`Caught exception: ${err}`);
 });
 setTimeout(common.mustCall(function() {
--- a/test/parallel/test-file-write-stream2.js
+++ b/test/parallel/test-file-write-stream2.js
@ -43,9 +43,9 @@ process.on('exit', function() {
    console.log('  Test callback events missing or out of order:');
    console.log('    expected: %j', cb_expected);
    console.log('    occurred: %j', cb_occurred);
-    assert.strictEqual(cb_occurred, cb_expected,
+    assert.strictEqual(
-                       'events missing or out of order: "' +
+      cb_occurred, cb_expected,
-                       cb_occurred + '" !== "' + cb_expected + '"');
+      `events missing or out of order: "${cb_occurred}" !== "${cb_expected}"`);
  } else {
    console.log('ok');
  }
@ -101,7 +101,7 @@ file.on('error', function(err) {
 for (let i = 0; i < 11; i++) {
-  const ret = file.write(i + '');
+  const ret = file.write(String(i));
  console.error('%d %j', i, ret);
  // return false when i hits 10
--- a/test/parallel/test-file-write-stream3.js
+++ b/test/parallel/test-file-write-stream3.js
@ -44,9 +44,9 @@ process.on('exit', function() {
    console.log('  Test callback events missing or out of order:');
    console.log('    expected: %j', cb_expected);
    console.log('    occurred: %j', cb_occurred);
-    assert.strictEqual(cb_occurred, cb_expected,
+    assert.strictEqual(
-                       'events missing or out of order: "' +
+      cb_occurred, cb_expected,
-                       cb_occurred + '" !== "' + cb_expected + '"');
+      `events missing or out of order: "${cb_occurred}" !== "${cb_expected}"`);
  }
 });
--- a/test/parallel/test-fs-append-file-sync.js
+++ b/test/parallel/test-fs-append-file-sync.js
@ -83,7 +83,7 @@ if (!common.isWindows) {
 const fileData4 = fs.readFileSync(filename4);
-assert.strictEqual(Buffer.byteLength('' + num) + currentFileData.length,
+assert.strictEqual(Buffer.byteLength(String(num)) + currentFileData.length,
                   fileData4.length);
 // test that appendFile accepts file descriptors
--- a/test/parallel/test-fs-append-file.js
+++ b/test/parallel/test-fs-append-file.js
@ -109,7 +109,7 @@ fs.appendFile(filename4, n, { mode: m }, function(e) {
  fs.readFile(filename4, function(e, buffer) {
    assert.ifError(e);
    ncallbacks++;
-    assert.strictEqual(Buffer.byteLength('' + n) + currentFileData.length,
+    assert.strictEqual(Buffer.byteLength(String(n)) + currentFileData.length,
                       buffer.length);
  });
 });
--- a/test/parallel/test-fs-buffertype-writesync.js
+++ b/test/parallel/test-fs-buffertype-writesync.js
@ -16,5 +16,5 @@ common.refreshTmpDir();
 v.forEach((value) => {
  const fd = fs.openSync(filePath, 'w');
  fs.writeSync(fd, value);
-  assert.strictEqual(fs.readFileSync(filePath).toString(), value + '');
+  assert.strictEqual(fs.readFileSync(filePath).toString(), String(value));
 });
--- a/test/parallel/test-fs-error-messages.js
+++ b/test/parallel/test-fs-error-messages.js
@ -225,7 +225,8 @@ try {
 }
 process.on('exit', function() {
-  assert.strictEqual(expected, errors.length,
+  assert.strictEqual(
-                     'Test fs sync exceptions raised, got ' + errors.length +
+    expected, errors.length,
-               ' expected ' + expected);
+    `Test fs sync exceptions raised, got ${errors.length} expected ${expected}`
  );
 });
--- a/test/parallel/test-fs-exists.js
+++ b/test/parallel/test-fs-exists.js
@ -29,9 +29,9 @@ fs.exists(f, common.mustCall(function(y) {
  assert.strictEqual(y, true);
 }));
-fs.exists(f + '-NO', common.mustCall(function(y) {
+fs.exists(`${f}-NO`, common.mustCall(function(y) {
  assert.strictEqual(y, false);
 }));
 assert(fs.existsSync(f));
-assert(!fs.existsSync(f + '-NO'));
+assert(!fs.existsSync(`${f}-NO`));
--- a/test/parallel/test-fs-mkdir.js
+++ b/test/parallel/test-fs-mkdir.js
@ -34,7 +34,7 @@ function unlink(pathname) {
 common.refreshTmpDir();
 {
-  const pathname = common.tmpDir + '/test1';
+  const pathname = `${common.tmpDir}/test1`;
  unlink(pathname);
@ -49,7 +49,7 @@ common.refreshTmpDir();
 }
 {
-  const pathname = common.tmpDir + '/test2';
+  const pathname = `${common.tmpDir}/test2`;
  unlink(pathname);
@ -64,7 +64,7 @@ common.refreshTmpDir();
 }
 {
-  const pathname = common.tmpDir + '/test3';
+  const pathname = `${common.tmpDir}/test3`;
  unlink(pathname);
  fs.mkdirSync(pathname);
--- a/test/parallel/test-fs-non-number-arguments-throw.js
+++ b/test/parallel/test-fs-non-number-arguments-throw.js
@ -29,6 +29,7 @@ assert.throws(function() {
              "start as string didn't throw an error for createWriteStream");
 saneEmitter.on('data', common.mustCall(function(data) {
-  assert.strictEqual(sanity, data.toString('utf8'), 'read ' +
+  assert.strictEqual(
-                     data.toString('utf8') + ' instead of ' + sanity);
+    sanity, data.toString('utf8'),
    `read ${data.toString('utf8')} instead of ${sanity}`);
 }));
--- a/test/parallel/test-fs-readdir.js
+++ b/test/parallel/test-fs-readdir.js
@ -12,7 +12,7 @@ common.refreshTmpDir();
 // Create the necessary files
 files.forEach(function(currentFile) {
-  fs.closeSync(fs.openSync(readdirDir + '/' + currentFile, 'w'));
+  fs.closeSync(fs.openSync(`${readdirDir}/${currentFile}`, 'w'));
 });
 // Check the readdir Sync version
--- a/test/parallel/test-fs-readfile-error.js
+++ b/test/parallel/test-fs-readfile-error.js
@ -34,13 +34,13 @@ if (common.isFreeBSD) {
 function test(env, cb) {
  const filename = path.join(common.fixturesDir, 'test-fs-readfile-error.js');
-  const execPath = '"' + process.execPath + '" "' + filename + '"';
+  const execPath = `"${process.execPath}" "${filename}"`;
  const options = { env: Object.assign(process.env, env) };
  exec(execPath, options, common.mustCall((err, stdout, stderr) => {
    assert(err);
    assert.strictEqual(stdout, '');
    assert.notStrictEqual(stderr, '');
-    cb('' + stderr);
+    cb(String(stderr));
  }));
 }
--- a/test/parallel/test-fs-realpath.js
+++ b/test/parallel/test-fs-realpath.js
@ -29,6 +29,7 @@ let async_completed = 0;
 let async_expected = 0;
 const unlink = [];
 let skipSymlinks = false;
 const tmpDir = common.tmpDir;
 common.refreshTmpDir();
@ -62,11 +63,11 @@ if (common.isWindows) {
 function tmp(p) {
-  return path.join(common.tmpDir, p);
+  return path.join(tmpDir, p);
 }
-const targetsAbsDir = path.join(common.tmpDir, 'targets');
+const targetsAbsDir = path.join(tmpDir, 'targets');
-const tmpAbsDir = common.tmpDir;
+const tmpAbsDir = tmpDir;
 // Set up targetsAbsDir and expected subdirectories
 fs.mkdirSync(targetsAbsDir);
@ -105,10 +106,10 @@ function test_simple_relative_symlink(callback) {
    common.skip('symlink test (no privs)');
    return runNextTest();
  }
-  const entry = common.tmpDir + '/symlink';
+  const entry = `${tmpDir}/symlink`;
-  const expected = common.tmpDir + '/cycles/root.js';
+  const expected = `${tmpDir}/cycles/root.js`;
  [
-    [entry, '../' + common.tmpDirName + '/cycles/root.js']
+    [entry, `../${common.tmpDirName}/cycles/root.js`]
  ].forEach(function(t) {
    try { fs.unlinkSync(t[0]); } catch (e) {}
    console.log('fs.symlinkSync(%j, %j, %j)', t[1], t[0], 'file');
@ -131,8 +132,8 @@ function test_simple_absolute_symlink(callback) {
  console.log('using type=%s', type);
-  const entry = tmpAbsDir + '/symlink';
+  const entry = `${tmpAbsDir}/symlink`;
-  const expected = common.fixturesDir + '/nested-index/one';
+  const expected = `${common.fixturesDir}/nested-index/one`;
  [
    [entry, expected]
  ].forEach(function(t) {
@ -212,11 +213,11 @@ function test_cyclic_link_protection(callback) {
    common.skip('symlink test (no privs)');
    return runNextTest();
  }
-  const entry = path.join(common.tmpDir, '/cycles/realpath-3a');
+  const entry = path.join(tmpDir, '/cycles/realpath-3a');
  [
    [entry, '../cycles/realpath-3b'],
-    [path.join(common.tmpDir, '/cycles/realpath-3b'), '../cycles/realpath-3c'],
+    [path.join(tmpDir, '/cycles/realpath-3b'), '../cycles/realpath-3c'],
-    [path.join(common.tmpDir, '/cycles/realpath-3c'), '../cycles/realpath-3a']
+    [path.join(tmpDir, '/cycles/realpath-3c'), '../cycles/realpath-3a']
  ].forEach(function(t) {
    try { fs.unlinkSync(t[0]); } catch (e) {}
    fs.symlinkSync(t[1], t[0], 'dir');
@ -239,10 +240,10 @@ function test_cyclic_link_overprotection(callback) {
    common.skip('symlink test (no privs)');
    return runNextTest();
  }
-  const cycles = common.tmpDir + '/cycles';
+  const cycles = `${tmpDir}/cycles`;
  const expected = fs.realpathSync(cycles);
-  const folder = cycles + '/folder';
+  const folder = `${cycles}/folder`;
-  const link = folder + '/cycles';
+  const link = `${folder}/cycles`;
  let testPath = cycles;
  testPath += '/folder/cycles'.repeat(10);
  try { fs.unlinkSync(link); } catch (ex) {}
@ -264,12 +265,12 @@ function test_relative_input_cwd(callback) {
  // we need to calculate the relative path to the tmp dir from cwd
  const entrydir = process.cwd();
  const entry = path.relative(entrydir,
-                              path.join(common.tmpDir + '/cycles/realpath-3a'));
+                              path.join(`${tmpDir}/cycles/realpath-3a`));
-  const expected = common.tmpDir + '/cycles/root.js';
+  const expected = `${tmpDir}/cycles/root.js`;
  [
    [entry, '../cycles/realpath-3b'],
-    [common.tmpDir + '/cycles/realpath-3b', '../cycles/realpath-3c'],
+    [`${tmpDir}/cycles/realpath-3b`, '../cycles/realpath-3c'],
-    [common.tmpDir + '/cycles/realpath-3c', 'root.js']
+    [`${tmpDir}/cycles/realpath-3c`, 'root.js']
  ].forEach(function(t) {
    const fn = t[0];
    console.error('fn=%j', fn);
@ -317,16 +318,16 @@ function test_deep_symlink_mix(callback) {
  fs.mkdirSync(tmp('node-test-realpath-d2'), 0o700);
  try {
    [
-      [entry, common.tmpDir + '/node-test-realpath-d1/foo'],
+      [entry, `${tmpDir}/node-test-realpath-d1/foo`],
      [tmp('node-test-realpath-d1'),
-       common.tmpDir + '/node-test-realpath-d2'],
+       `${tmpDir}/node-test-realpath-d2`],
      [tmp('node-test-realpath-d2/foo'), '../node-test-realpath-f2'],
-      [tmp('node-test-realpath-f2'), targetsAbsDir +
+      [tmp('node-test-realpath-f2'),
-        '/nested-index/one/realpath-c'],
+       `${targetsAbsDir}/nested-index/one/realpath-c`],
-      [targetsAbsDir + '/nested-index/one/realpath-c', targetsAbsDir +
+      [`${targetsAbsDir}/nested-index/one/realpath-c`,
-        '/nested-index/two/realpath-c'],
+       `${targetsAbsDir}/nested-index/two/realpath-c`],
-      [targetsAbsDir + '/nested-index/two/realpath-c',
+      [`${targetsAbsDir}/nested-index/two/realpath-c`,
-       common.tmpDir + '/cycles/root.js']
+       `${tmpDir}/cycles/root.js`]
    ].forEach(function(t) {
      try { fs.unlinkSync(t[0]); } catch (e) {}
      fs.symlinkSync(t[1], t[0]);
@ -335,7 +336,7 @@ function test_deep_symlink_mix(callback) {
  } finally {
    unlink.push(tmp('node-test-realpath-d2'));
  }
-  const expected = tmpAbsDir + '/cycles/root.js';
+  const expected = `${tmpAbsDir}/cycles/root.js`;
  assertEqualPath(fs.realpathSync(entry), path.resolve(expected));
  asynctest(fs.realpath, [entry], callback, function(err, result) {
    assertEqualPath(result, path.resolve(expected));
@ -346,8 +347,8 @@ function test_deep_symlink_mix(callback) {
 function test_non_symlinks(callback) {
  console.log('test_non_symlinks');
  const entrydir = path.dirname(tmpAbsDir);
-  const entry = tmpAbsDir.substr(entrydir.length + 1) + '/cycles/root.js';
+  const entry = `${tmpAbsDir.substr(entrydir.length + 1)}/cycles/root.js`;
-  const expected = tmpAbsDir + '/cycles/root.js';
+  const expected = `${tmpAbsDir}/cycles/root.js`;
  const origcwd = process.cwd();
  process.chdir(entrydir);
  assertEqualPath(fs.realpathSync(entry), path.resolve(expected));
@ -362,15 +363,15 @@ const upone = path.join(process.cwd(), '..');
 function test_escape_cwd(cb) {
  console.log('test_escape_cwd');
  asynctest(fs.realpath, ['..'], cb, function(er, uponeActual) {
-    assertEqualPath(upone, uponeActual,
+    assertEqualPath(
-                    'realpath("..") expected: ' + path.resolve(upone) +
+      upone, uponeActual,
-                    ' actual:' + uponeActual);
+      `realpath("..") expected: ${path.resolve(upone)} actual:${uponeActual}`);
  });
 }
 const uponeActual = fs.realpathSync('..');
-assertEqualPath(upone, uponeActual,
+assertEqualPath(
-                'realpathSync("..") expected: ' + path.resolve(upone) +
+  upone, uponeActual,
-                ' actual:' + uponeActual);
+  `realpathSync("..") expected: ${path.resolve(upone)} actual:${uponeActual}`);
 // going up with .. multiple times
@ -442,7 +443,7 @@ function test_abs_with_kids(cb) {
  console.log('using type=%s', type);
-  const root = tmpAbsDir + '/node-test-realpath-abs-kids';
+  const root = `${tmpAbsDir}/node-test-realpath-abs-kids`;
  function cleanup() {
    ['/a/b/c/x.txt',
     '/a/link'
@ -464,15 +465,15 @@ function test_abs_with_kids(cb) {
     '/a/b',
     '/a/b/c'
    ].forEach(function(folder) {
-      console.log('mkdir ' + root + folder);
+      console.log(`mkdir ${root}${folder}`);
      fs.mkdirSync(root + folder, 0o700);
    });
-    fs.writeFileSync(root + '/a/b/c/x.txt', 'foo');
+    fs.writeFileSync(`${root}/a/b/c/x.txt`, 'foo');
-    fs.symlinkSync(root + '/a/b', root + '/a/link', type);
+    fs.symlinkSync(`${root}/a/b`, `${root}/a/link`, type);
  }
  setup();
-  const linkPath = root + '/a/link/c/x.txt';
+  const linkPath = `${root}/a/link/c/x.txt`;
-  const expectPath = root + '/a/b/c/x.txt';
+  const expectPath = `${root}/a/b/c/x.txt`;
  const actual = fs.realpathSync(linkPath);
  // console.log({link:linkPath,expect:expectPath,actual:actual},'sync');
  assertEqualPath(actual, path.resolve(expectPath));
@ -506,8 +507,7 @@ function runNextTest(err) {
  assert.ifError(err);
  const test = tests.shift();
  if (!test) {
-    return console.log(numtests +
+    return console.log(`${numtests} subtests completed OK for fs.realpath`);
                       ' subtests completed OK for fs.realpath');
  }
  testsRun++;
  test(runNextTest);
--- a/test/parallel/test-fs-sir-writes-alot.js
+++ b/test/parallel/test-fs-sir-writes-alot.js
@ -56,7 +56,7 @@ function testBuffer(b) {
  for (let i = 0; i < b.length; i++) {
    bytesChecked++;
    if (b[i] !== 'a'.charCodeAt(0) && b[i] !== '\n'.charCodeAt(0)) {
-      throw new Error('invalid char ' + i + ',' + b[i]);
+      throw new Error(`invalid char ${i},${b[i]}`);
    }
  }
 }
--- a/test/parallel/test-fs-stat.js
+++ b/test/parallel/test-fs-stat.js
@ -77,25 +77,25 @@ fs.stat(__filename, common.mustCall(function(err, s) {
  console.dir(s);
-  console.log('isDirectory: ' + JSON.stringify(s.isDirectory()));
+  console.log(`isDirectory: ${JSON.stringify(s.isDirectory())}`);
  assert.strictEqual(false, s.isDirectory());
-  console.log('isFile: ' + JSON.stringify(s.isFile()));
+  console.log(`isFile: ${JSON.stringify(s.isFile())}`);
  assert.strictEqual(true, s.isFile());
-  console.log('isSocket: ' + JSON.stringify(s.isSocket()));
+  console.log(`isSocket: ${JSON.stringify(s.isSocket())}`);
  assert.strictEqual(false, s.isSocket());
-  console.log('isBlockDevice: ' + JSON.stringify(s.isBlockDevice()));
+  console.log(`isBlockDevice: ${JSON.stringify(s.isBlockDevice())}`);
  assert.strictEqual(false, s.isBlockDevice());
-  console.log('isCharacterDevice: ' + JSON.stringify(s.isCharacterDevice()));
+  console.log(`isCharacterDevice: ${JSON.stringify(s.isCharacterDevice())}`);
  assert.strictEqual(false, s.isCharacterDevice());
-  console.log('isFIFO: ' + JSON.stringify(s.isFIFO()));
+  console.log(`isFIFO: ${JSON.stringify(s.isFIFO())}`);
  assert.strictEqual(false, s.isFIFO());
-  console.log('isSymbolicLink: ' + JSON.stringify(s.isSymbolicLink()));
+  console.log(`isSymbolicLink: ${JSON.stringify(s.isSymbolicLink())}`);
  assert.strictEqual(false, s.isSymbolicLink());
  assert.ok(s.mtime instanceof Date);
--- a/test/parallel/test-fs-stream-double-close.js
+++ b/test/parallel/test-fs-stream-double-close.js
@ -29,9 +29,9 @@ test1(fs.createReadStream(__filename));
 test2(fs.createReadStream(__filename));
 test3(fs.createReadStream(__filename));
-test1(fs.createWriteStream(common.tmpDir + '/dummy1'));
+test1(fs.createWriteStream(`${common.tmpDir}/dummy1`));
-test2(fs.createWriteStream(common.tmpDir + '/dummy2'));
+test2(fs.createWriteStream(`${common.tmpDir}/dummy2`));
-test3(fs.createWriteStream(common.tmpDir + '/dummy3'));
+test3(fs.createWriteStream(`${common.tmpDir}/dummy3`));
 function test1(stream) {
  stream.destroy();
--- a/test/parallel/test-fs-symlink-dir-junction-relative.js
+++ b/test/parallel/test-fs-symlink-dir-junction-relative.js
@ -48,8 +48,8 @@ function verifyLink(linkPath) {
  const stats = fs.lstatSync(linkPath);
  assert.ok(stats.isSymbolicLink());
-  const data1 = fs.readFileSync(linkPath + '/x.txt', 'ascii');
+  const data1 = fs.readFileSync(`${linkPath}/x.txt`, 'ascii');
-  const data2 = fs.readFileSync(linkTarget + '/x.txt', 'ascii');
+  const data2 = fs.readFileSync(`${linkTarget}/x.txt`, 'ascii');
  assert.strictEqual(data1, data2);
  // Clean up.
--- a/test/parallel/test-fs-symlink-dir-junction.js
+++ b/test/parallel/test-fs-symlink-dir-junction.js
@ -31,8 +31,8 @@ const linkPath = path.join(common.tmpDir, 'cycles_link');
 common.refreshTmpDir();
-console.log('linkData: ' + linkData);
+console.log(`linkData: ${linkData}`);
-console.log('linkPath: ' + linkPath);
+console.log(`linkPath: ${linkPath}`);
 fs.symlink(linkData, linkPath, 'junction', common.mustCall(function(err) {
  assert.ifError(err);
--- a/test/parallel/test-fs-timestamp-parsing-error.js
+++ b/test/parallel/test-fs-timestamp-parsing-error.js
@ -5,7 +5,7 @@ const assert = require('assert');
 [Infinity, -Infinity, NaN].forEach((input) => {
  assert.throws(() => fs._toUnixTimestamp(input),
-                new RegExp('^Error: Cannot parse time: ' + input + '$'));
+                new RegExp(`^Error: Cannot parse time: ${input}$`));
 });
 assert.throws(() => fs._toUnixTimestamp({}),
--- a/test/parallel/test-fs-truncate-GH-6233.js
+++ b/test/parallel/test-fs-truncate-GH-6233.js
@ -24,7 +24,7 @@ const common = require('../common');
 const assert = require('assert');
 const fs = require('fs');
-const filename = common.tmpDir + '/truncate-file.txt';
+const filename = `${common.tmpDir}/truncate-file.txt`;
 common.refreshTmpDir();
--- a/test/parallel/test-fs-write-file.js
+++ b/test/parallel/test-fs-write-file.js
@ -77,7 +77,7 @@ fs.writeFile(filename3, n, { mode: m }, common.mustCall(function(e) {
  fs.readFile(filename3, common.mustCall(function(e, buffer) {
    assert.ifError(e);
-    assert.strictEqual(Buffer.byteLength('' + n), buffer.length);
+    assert.strictEqual(Buffer.byteLength(String(n)), buffer.length);
  }));
 }));
--- a/test/parallel/test-fs-write-stream-err.js
+++ b/test/parallel/test-fs-write-stream-err.js
@ -26,7 +26,7 @@ const fs = require('fs');
 common.refreshTmpDir();
-const stream = fs.createWriteStream(common.tmpDir + '/out', {
+const stream = fs.createWriteStream(`${common.tmpDir}/out`, {
  highWaterMark: 10
 });
 const err = new Error('BAM');
--- a/test/parallel/test-fs-write-string-coerce.js
+++ b/test/parallel/test-fs-write-string-coerce.js
@ -9,7 +9,7 @@ common.refreshTmpDir();
 const fn = path.join(common.tmpDir, 'write-string-coerce.txt');
 const data = true;
-const expected = data + '';
+const expected = String(data);
 fs.open(fn, 'w', 0o644, common.mustCall(function(err, fd) {
  assert.ifError(err);
--- a/test/parallel/test-http-abort-client.js
+++ b/test/parallel/test-http-abort-client.js
@ -38,11 +38,11 @@ server.listen(0, common.mustCall(function() {
  }, common.mustCall(function(res) {
    server.close();
-    console.log('Got res: ' + res.statusCode);
+    console.log(`Got res: ${res.statusCode}`);
    console.dir(res.headers);
    res.on('data', function(chunk) {
-      console.log('Read ' + chunk.length + ' bytes');
+      console.log(`Read ${chunk.length} bytes`);
      console.log(' chunk=%j', chunk.toString());
    });
--- a/test/parallel/test-http-abort-queued.js
+++ b/test/parallel/test-http-abort-queued.js
@ -80,11 +80,11 @@ server.listen(0, function() {
    assert.strictEqual(Object.keys(agent.sockets).length, 1);
    assert.strictEqual(Object.keys(agent.requests).length, 1);
-    console.log('Got res: ' + res1.statusCode);
+    console.log(`Got res: ${res1.statusCode}`);
    console.dir(res1.headers);
    res1.on('data', function(chunk) {
-      console.log('Read ' + chunk.length + ' bytes');
+      console.log(`Read ${chunk.length} bytes`);
      console.log(' chunk=%j', chunk.toString());
      complete();
    });
--- a/test/parallel/test-http-after-connect.js
+++ b/test/parallel/test-http-after-connect.js
@ -64,7 +64,7 @@ server.listen(0, function() {
 function doRequest(i) {
  http.get({
    port: server.address().port,
-    path: '/request' + i
+    path: `/request${i}`
  }, common.mustCall(function(res) {
    console.error('Client got GET response');
    let data = '';
@ -73,7 +73,7 @@ function doRequest(i) {
      data += chunk;
    });
    res.on('end', function() {
-      assert.strictEqual(data, '/request' + i);
+      assert.strictEqual(data, `/request${i}`);
      ++clientResponses;
      if (clientResponses === 2) {
        server.close();
--- a/test/parallel/test-http-agent-error-on-idle.js
+++ b/test/parallel/test-http-agent-error-on-idle.js
@ -29,7 +29,7 @@ server.listen(0, function() {
      process.nextTick(function() {
        const freeSockets = agent.freeSockets[socketKey];
        assert.strictEqual(freeSockets.length, 1,
-                           'expect a free socket on ' + socketKey);
+                           `expect a free socket on ${socketKey}`);
        //generate a random error on the free socket
        const freeSocket = freeSockets[0];
--- a/test/parallel/test-http-agent-getname.js
+++ b/test/parallel/test-http-agent-getname.js
@ -35,4 +35,4 @@ for (const family of [0, null, undefined, 'bogus'])
  assert.strictEqual(agent.getName({ family }), 'localhost::');
 for (const family of [4, 6])
-  assert.strictEqual(agent.getName({ family }), 'localhost:::' + family);
+  assert.strictEqual(agent.getName({ family }), `localhost:::${family}`);
--- a/test/parallel/test-http-agent-maxsockets.js
+++ b/test/parallel/test-http-agent-maxsockets.js
@ -30,7 +30,7 @@ function done() {
  }
  const freepool = agent.freeSockets[Object.keys(agent.freeSockets)[0]];
  assert.strictEqual(freepool.length, 2,
-                     'expect keep 2 free sockets, but got ' + freepool.length);
+                     `expect keep 2 free sockets, but got ${freepool.length}`);
  agent.destroy();
  server.close();
 }
--- a/test/parallel/test-http-buffer-sanity.js
+++ b/test/parallel/test-http-buffer-sanity.js
@ -58,7 +58,7 @@ const web = http.Server(function(req, res) {
  });
  req.connection.on('error', function(e) {
-    console.log('http server-side error: ' + e.message);
+    console.log(`http server-side error: ${e.message}`);
    process.exit(1);
  });
 });
--- a/test/parallel/test-http-chunk-problem.js
+++ b/test/parallel/test-http-chunk-problem.js
@ -82,7 +82,7 @@ cp.exec(ddcmd, function(err, stdout, stderr) {
    // End the response on exit (and log errors)
    cat.on('exit', (code) => {
      if (code !== 0) {
-        console.error('subprocess exited with code ' + code);
+        console.error(`subprocess exited with code ${code}`);
        process.exit(1);
      }
    });
--- a/test/parallel/test-http-client-abort.js
+++ b/test/parallel/test-http-client-abort.js
@ -36,7 +36,7 @@ const server = http.Server(function(req, res) {
  // event like "aborted" or something.
  req.on('aborted', function() {
    clientAborts++;
-    console.log('Got abort ' + clientAborts);
+    console.log(`Got abort ${clientAborts}`);
    if (clientAborts === N) {
      console.log('All aborts detected, you win.');
      server.close();
@ -52,10 +52,10 @@ server.listen(0, function() {
  console.log('Server listening.');
  for (let i = 0; i < N; i++) {
-    console.log('Making client ' + i);
+    console.log(`Making client ${i}`);
-    const options = { port: this.address().port, path: '/?id=' + i };
+    const options = { port: this.address().port, path: `/?id=${i}` };
    const req = http.get(options, function(res) {
-      console.log('Client response code ' + res.statusCode);
+      console.log(`Client response code ${res.statusCode}`);
      res.resume();
      if (++responses === N) {
--- a/test/parallel/test-http-client-agent.js
+++ b/test/parallel/test-http-client-agent.js
@ -49,7 +49,7 @@ server.listen(0, function() {
 function request(i) {
  const req = http.get({
    port: server.address().port,
-    path: '/' + i
+    path: `/${i}`
  }, function(res) {
    const socket = req.socket;
    socket.on('close', function() {