test: fix flaky test-vm-sigint-existing-handler

Set the `SIGUSR2` handler before spawning the child process to make sure the signal is always handled. Ref: #7854 Fixes: #7981 PR-URL: #7982 Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com> Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

Author: addaleax

test/parallel/test-vm-sigint-existing-handler.js

@@ -61,16 +61,19 @@ if (process.argv[2] === 'child') {
 }
 
 process.env.REPL_TEST_PPID = process.pid;
-const child = spawn(process.execPath, [ __filename, 'child' ], {
- stdio: [null, 'inherit', 'inherit']
-});
 
+// Set the `SIGUSR2` handler before spawning the child process to make sure
+// the signal is always handled.
 process.on('SIGUSR2', common.mustCall(() => {
  // First kill() breaks the while(true) loop, second one invokes the real
  // signal handlers.
  process.kill(child.pid, 'SIGINT');
 }, 3));
 
+const child = spawn(process.execPath, [__filename, 'child'], {
+ stdio: [null, 'inherit', 'inherit']
+});
+
 child.on('close', function(code, signal) {
  assert.strictEqual(signal, null);
  assert.strictEqual(code, 0);

test/parallel/test-vm-sigint.js

@@ -25,11 +25,14 @@ if (process.argv[2] === 'child') {
 }
 
 process.env.REPL_TEST_PPID = process.pid;
+
+// Set the `SIGUSR2` handler before spawning the child process to make sure
+// the signal is always handled.
 process.on('SIGUSR2', common.mustCall(() => {
  process.kill(child.pid, 'SIGINT');
 }));
 
-const child = spawn(process.execPath, [ __filename, 'child' ], {
+const child = spawn(process.execPath, [__filename, 'child'], {
  stdio: [null, 'pipe', 'inherit']
 });