test: preserve env in test cases

Allows env vars to be passed through to child processes. This is needed
for things like NODE_TEST_DIR or LD_LIBRARY_PATH if testing the shared
library.

Backport-PR-URL: #18883
PR-URL: #14822
Refs: #13390
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/parallel/test-env-var-no-warnings.js

@@ -6,7 +6,8 @@ const cp = require('child_process');
 if (process.argv[2] === 'child') {
   process.emitWarning('foo');
 } else {
-  function test(env) {
+  function test(newEnv) {
+    const env = Object.assign({}, process.env, newEnv);
     const cmd = `"${process.execPath}" "${__filename}" child`;
 
     cp.exec(cmd, { env }, common.mustCall((err, stdout, stderr) => {

test/parallel/test-tls-env-bad-extra-ca.js

@@ -16,10 +16,10 @@ if (process.env.CHILD) {
   return tls.createServer({});
 }
 
-const env = {
+const env = Object.assign({}, process.env, {
   CHILD: 'yes',
-  NODE_EXTRA_CA_CERTS: `${fixtures.fixturesDir}/no-such-file-exists`
-};
+  NODE_EXTRA_CA_CERTS: `${fixtures.fixturesDir}/no-such-file-exists`,
+});
 
 const opts = {
   env: env,

test/parallel/test-tls-env-extra-ca.js

@@ -32,11 +32,11 @@ const server = tls.createServer(options, common.mustCall(function(s) {
   s.end('bye');
   server.close();
 })).listen(0, common.mustCall(function() {
-  const env = {
+  const env = Object.assign({}, process.env, {
     CHILD: 'yes',
     PORT: this.address().port,
     NODE_EXTRA_CA_CERTS: fixtures.path('keys', 'ca1-cert.pem')
-  };
+  });
 
   fork(__filename, {env: env}).on('exit', common.mustCall(function(status) {
     assert.strictEqual(status, 0, 'client did not succeed in connecting');