diff --git a/test/parallel/test-benchmark-crypto.js b/test/parallel/test-benchmark-crypto.js
index 5750a4e2afdadf..3675c38b9ea280 100644
--- a/test/parallel/test-benchmark-crypto.js
+++ b/test/parallel/test-benchmark-crypto.js
@@ -26,9 +26,10 @@ const argv = ['--set', 'algo=sha256',
               '--set', 'v=crypto',
               '--set', 'writes=1',
               'crypto'];
-const env = Object.assign({}, process.env,
-                          { NODEJS_BENCHMARK_ZERO_ALLOWED: 1 });
-const child = fork(runjs, argv, { env });
+
+const child = fork(runjs, argv, { env: Object.assign({}, process.env, {
+  NODEJS_BENCHMARK_ZERO_ALLOWED: 1 }) });
+
 child.on('exit', (code, signal) => {
   assert.strictEqual(code, 0);
   assert.strictEqual(signal, null);
diff --git a/test/parallel/test-child-process-env.js b/test/parallel/test-child-process-env.js
index 65e2bb3f163a6a..4582c48fda5db1 100644
--- a/test/parallel/test-child-process-env.js
+++ b/test/parallel/test-child-process-env.js
@@ -34,9 +34,11 @@ Object.setPrototypeOf(env, {
 
 let child;
 if (common.isWindows) {
-  child = spawn('cmd.exe', ['/c', 'set'], { env: env });
+  child = spawn('cmd.exe', ['/c', 'set'],
+                Object.assign({}, process.env, { env: env }));
 } else {
-  child = spawn('/usr/bin/env', [], { env: env });
+  child = spawn('/usr/bin/env', [],
+                Object.assign({}, process.env, { env: env }));
 }
 
 
diff --git a/test/parallel/test-child-process-exec-env.js b/test/parallel/test-child-process-exec-env.js
index 3b1ef741e6c9b2..c34fdb7b49a161 100644
--- a/test/parallel/test-child-process-exec-env.js
+++ b/test/parallel/test-child-process-exec-env.js
@@ -44,7 +44,9 @@ function after(err, stdout, stderr) {
 if (!common.isWindows) {
   child = exec('/usr/bin/env', { env: { 'HELLO': 'WORLD' } }, after);
 } else {
-  child = exec('set', { env: { 'HELLO': 'WORLD' } }, after);
+  child = exec('set',
+               { env: Object.assign({}, process.env, { 'HELLO': 'WORLD' }) },
+               after);
 }
 
 child.stdout.setEncoding('utf8');
diff --git a/test/parallel/test-cli-node-options.js b/test/parallel/test-cli-node-options.js
index eb31e280c3d47b..f52497e80839cb 100644
--- a/test/parallel/test-cli-node-options.js
+++ b/test/parallel/test-cli-node-options.js
@@ -29,7 +29,8 @@ disallow('--');
 disallow('--no_warnings'); // Node options don't allow '_' instead of '-'.
 
 function disallow(opt) {
-  const options = { env: { NODE_OPTIONS: opt } };
+  const options = { env: Object.assign({}, process.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} is not allowed in NODE_OPTIONS`;
@@ -71,7 +72,7 @@ function expect(opt, want) {
   const printB = require.resolve('../fixtures/printB.js');
   const argv = [printB];
   const opts = {
-    env: { NODE_OPTIONS: opt },
+    env: Object.assign({}, process.env, { NODE_OPTIONS: opt }),
     maxBuffer: 1000000000,
   };
   exec(process.execPath, argv, opts, common.mustCall(function(err, stdout) {
diff --git a/test/parallel/test-crypto-fips.js b/test/parallel/test-crypto-fips.js
index d72918756a200b..da2dd7b0ba8765 100644
--- a/test/parallel/test-crypto-fips.js
+++ b/test/parallel/test-crypto-fips.js
@@ -26,15 +26,6 @@ function sharedOpenSSL() {
   return process.config.variables.node_shared_openssl;
 }
 
-function addToEnv(newVar, value) {
-  const envCopy = {};
-  for (const e in process.env) {
-    envCopy[e] = process.env[e];
-  }
-  envCopy[newVar] = value;
-  return envCopy;
-}
-
 function testHelper(stream, args, expectedOutput, cmd, env) {
   const fullArgs = args.concat(['-e', `console.log(${cmd})`]);
   const child = spawnSync(process.execPath, fullArgs, {
@@ -72,7 +63,7 @@ testHelper(
   [],
   FIPS_DISABLED,
   'require("crypto").fips',
-  addToEnv('OPENSSL_CONF', ''));
+  Object.assign({}, process.env, { 'OPENSSL_CONF': '' }));
 
 // --enable-fips should turn FIPS mode on
 testHelper(
@@ -117,7 +108,7 @@ if (!sharedOpenSSL()) {
     [],
     compiledWithFips() ? FIPS_ENABLED : FIPS_DISABLED,
     'require("crypto").fips',
-    addToEnv('OPENSSL_CONF', CNF_FIPS_ON));
+    Object.assign({}, process.env, { 'OPENSSL_CONF': CNF_FIPS_ON }));
 
   // --openssl-config option should override OPENSSL_CONF
   testHelper(
@@ -125,7 +116,7 @@ if (!sharedOpenSSL()) {
     [`--openssl-config=${CNF_FIPS_ON}`],
     compiledWithFips() ? FIPS_ENABLED : FIPS_DISABLED,
     'require("crypto").fips',
-    addToEnv('OPENSSL_CONF', CNF_FIPS_OFF));
+    Object.assign({}, process.env, { 'OPENSSL_CONF': CNF_FIPS_OFF }));
 }
 
 testHelper(
@@ -133,7 +124,7 @@ testHelper(
   [`--openssl-config=${CNF_FIPS_OFF}`],
   FIPS_DISABLED,
   'require("crypto").fips',
-  addToEnv('OPENSSL_CONF', CNF_FIPS_ON));
+  Object.assign({}, process.env, { 'OPENSSL_CONF': CNF_FIPS_ON }));
 
 // --enable-fips should take precedence over OpenSSL config file
 testHelper(
@@ -149,7 +140,7 @@ testHelper(
   ['--enable-fips'],
   compiledWithFips() ? FIPS_ENABLED : OPTION_ERROR_STRING,
   'require("crypto").fips',
-  addToEnv('OPENSSL_CONF', CNF_FIPS_OFF));
+  Object.assign({}, process.env, { 'OPENSSL_CONF': CNF_FIPS_OFF }));
 
 // --force-fips should take precedence over OpenSSL config file
 testHelper(
@@ -165,7 +156,7 @@ testHelper(
   ['--force-fips'],
   compiledWithFips() ? FIPS_ENABLED : OPTION_ERROR_STRING,
   'require("crypto").fips',
-  addToEnv('OPENSSL_CONF', CNF_FIPS_OFF));
+  Object.assign({}, process.env, { 'OPENSSL_CONF': CNF_FIPS_OFF }));
 
 // setFipsCrypto should be able to turn FIPS mode on
 testHelper(
diff --git a/test/parallel/test-fs-readfile-error.js b/test/parallel/test-fs-readfile-error.js
index aa6e6bdecb0b08..e7c52f19a83d1c 100644
--- a/test/parallel/test-fs-readfile-error.js
+++ b/test/parallel/test-fs-readfile-error.js
@@ -33,7 +33,7 @@ const fixtures = require('../common/fixtures');
 function test(env, cb) {
   const filename = fixtures.path('test-fs-readfile-error.js');
   const execPath = `"${process.execPath}" "${filename}"`;
-  const options = { env: Object.assign(process.env, env) };
+  const options = { env: Object.assign({}, process.env, env) };
   exec(execPath, options, common.mustCall((err, stdout, stderr) => {
     assert(err);
     assert.strictEqual(stdout, '');
diff --git a/test/parallel/test-http-server-stale-close.js b/test/parallel/test-http-server-stale-close.js
index 1f3c4595d4d251..b72c2b55a02f25 100644
--- a/test/parallel/test-http-server-stale-close.js
+++ b/test/parallel/test-http-server-stale-close.js
@@ -22,7 +22,6 @@
 'use strict';
 require('../common');
 const http = require('http');
-const util = require('util');
 const fork = require('child_process').fork;
 
 if (process.env.NODE_TEST_FORK_PORT) {
@@ -45,7 +44,7 @@ if (process.env.NODE_TEST_FORK_PORT) {
   });
   server.listen(0, function() {
     fork(__filename, {
-      env: util._extend(process.env, {
+      env: Object.assign({}, process.env, {
         NODE_TEST_FORK_PORT: this.address().port
       })
     });
diff --git a/test/parallel/test-icu-data-dir.js b/test/parallel/test-icu-data-dir.js
index 1a97699ca51691..800e20c48bab03 100644
--- a/test/parallel/test-icu-data-dir.js
+++ b/test/parallel/test-icu-data-dir.js
@@ -17,7 +17,7 @@ const expected =
 }
 
 {
-  const env = { NODE_ICU_DATA: '/' };
+  const env = Object.assign({}, process.env, { NODE_ICU_DATA: '/' });
   const child = spawnSync(process.execPath, ['-e', '0'], { env });
   assert(child.stderr.toString().includes(expected));
 }
diff --git a/test/parallel/test-inspector-open.js b/test/parallel/test-inspector-open.js
index e01d332e0348ba..a0d2eaf1f3415a 100644
--- a/test/parallel/test-inspector-open.js
+++ b/test/parallel/test-inspector-open.js
@@ -13,7 +13,8 @@ const url = require('url');
 if (process.env.BE_CHILD)
   return beChild();
 
-const child = fork(__filename, { env: { BE_CHILD: 1 } });
+const child = fork(__filename,
+                   { env: Object.assign({}, process.env, { BE_CHILD: 1 }) });
 
 child.once('message', common.mustCall((msg) => {
   assert.strictEqual(msg.cmd, 'started');
diff --git a/test/parallel/test-npm-install.js b/test/parallel/test-npm-install.js
index 1faa698b15fc22..9dcb5e8d1cda62 100644
--- a/test/parallel/test-npm-install.js
+++ b/test/parallel/test-npm-install.js
@@ -39,11 +39,12 @@ const pkgPath = path.join(installDir, 'package.json');
 
 fs.writeFileSync(pkgPath, pkgContent);
 
-const env = Object.create(process.env);
-env['PATH'] = path.dirname(process.execPath);
-env['NPM_CONFIG_PREFIX'] = path.join(npmSandbox, 'npm-prefix');
-env['NPM_CONFIG_TMP'] = path.join(npmSandbox, 'npm-tmp');
-env['HOME'] = path.join(npmSandbox, 'home');
+const env = Object.assign({}, process.env, {
+  PATH: path.dirname(process.execPath),
+  NPM_CONFIG_PREFIX: path.join(npmSandbox, 'npm-prefix'),
+  NPM_CONFIG_TMP: path.join(npmSandbox, 'npm-tmp'),
+  HOME: path.join(npmSandbox, 'home'),
+});
 
 const proc = spawn(process.execPath, args, {
   cwd: installDir,
diff --git a/test/parallel/test-pending-deprecation.js b/test/parallel/test-pending-deprecation.js
index fedc7c96b83e6b..9b1fd5addfa0c6 100644
--- a/test/parallel/test-pending-deprecation.js
+++ b/test/parallel/test-pending-deprecation.js
@@ -37,7 +37,7 @@ switch (process.argv[2]) {
 
     // Test the NODE_PENDING_DEPRECATION environment var.
     fork(__filename, ['env'], {
-      env: { NODE_PENDING_DEPRECATION: 1 },
+      env: Object.assign({}, process.env, { NODE_PENDING_DEPRECATION: 1 }),
       silent: true
     }).on('exit', common.mustCall((code) => {
       assert.strictEqual(code, 0, message('NODE_PENDING_DEPRECATION'));
diff --git a/test/parallel/test-process-redirect-warnings-env.js b/test/parallel/test-process-redirect-warnings-env.js
index 6878024e7955b7..6748723cfe0bf3 100644
--- a/test/parallel/test-process-redirect-warnings-env.js
+++ b/test/parallel/test-process-redirect-warnings-env.js
@@ -16,7 +16,8 @@ common.refreshTmpDir();
 const warnmod = require.resolve(`${common.fixturesDir}/warnings.js`);
 const warnpath = path.join(common.tmpDir, 'warnings.txt');
 
-fork(warnmod, { env: { NODE_REDIRECT_WARNINGS: warnpath } })
+fork(warnmod, { env: Object.assign({}, process.env,
+                                   { NODE_REDIRECT_WARNINGS: warnpath }) })
   .on('exit', common.mustCall(() => {
     fs.readFile(warnpath, 'utf8', common.mustCall((err, data) => {
       assert.ifError(err);
diff --git a/test/parallel/test-repl-envvars.js b/test/parallel/test-repl-envvars.js
index c4efd184c4c91c..d29e7b3574c1f2 100644
--- a/test/parallel/test-repl-envvars.js
+++ b/test/parallel/test-repl-envvars.js
@@ -36,7 +36,7 @@ const tests = [
 ];
 
 function run(test) {
-  const env = test.env;
+  const env = Object.assign({}, process.env, test.env);
   const expected = test.expected;
   const opts = {
     terminal: true,
diff --git a/test/parallel/test-require-symlink.js b/test/parallel/test-require-symlink.js
index 8f15845947ca67..4dd9bf51ed9213 100644
--- a/test/parallel/test-require-symlink.js
+++ b/test/parallel/test-require-symlink.js
@@ -5,7 +5,6 @@ const assert = require('assert');
 const path = require('path');
 const fs = require('fs');
 const { exec, spawn } = require('child_process');
-const util = require('util');
 const fixtures = require('../common/fixtures');
 
 common.refreshTmpDir();
@@ -61,7 +60,7 @@ function test() {
 
   // Also verify that symlinks works for setting preserve via env variables
   const childEnv = spawn(node, [linkScript], {
-    env: util._extend(process.env, { NODE_PRESERVE_SYMLINKS: '1' })
+    env: Object.assign({}, process.env, { NODE_PRESERVE_SYMLINKS: '1' })
   });
   childEnv.on('close', function(code, signal) {
     assert.strictEqual(code, 0);
diff --git a/test/parallel/test-stdin-script-child.js b/test/parallel/test-stdin-script-child.js
index 6e37fad9414de4..06adc9e113eda7 100644
--- a/test/parallel/test-stdin-script-child.js
+++ b/test/parallel/test-stdin-script-child.js
@@ -5,7 +5,7 @@ const assert = require('assert');
 const { spawn } = require('child_process');
 for (const args of [[], ['-']]) {
   const child = spawn(process.execPath, args, {
-    env: Object.assign(process.env, {
+    env: Object.assign({}, process.env, {
       NODE_DEBUG: process.argv[2]
     })
   });