test: add coverage for vm's breakOnSigint option

The breakOnSigint option follows different code paths, depending
on the number of listeners for SIGINT. This commit updates the
existing test to vary the number of SIGINT handlers.

PR-URL: https://github.com/nodejs/node/pull/12512
Reviewed-By: David Cai <davidcai1993@yahoo.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/parallel/test-vm-sigint.js

@@ -5,11 +5,6 @@ const vm = require('vm');
 
 const spawn = require('child_process').spawn;
 
-const methods = [
-  'runInThisContext',
-  'runInContext'
-];
-
 if (common.isWindows) {
   // No way to send CTRL_C_EVENT to processes from JS right now.
   common.skip('platform not supported');
@@ -18,7 +13,9 @@ if (common.isWindows) {
 
 if (process.argv[2] === 'child') {
   const method = process.argv[3];
+  const listeners = +process.argv[4];
   assert.ok(method);
+  assert.ok(typeof listeners, 'number');
 
   const script = `process.send('${method}'); while(true) {}`;
   const args = method === 'runInContext' ?
@@ -26,23 +23,28 @@ if (process.argv[2] === 'child') {
                           [];
   const options = { breakOnSigint: true };
 
+  for (let i = 0; i < listeners; i++)
+    process.on('SIGINT', common.noop);
+
   assert.throws(() => { vm[method](script, ...args, options); },
                 /^Error: Script execution interrupted\.$/);
-
   return;
 }
 
-for (const method of methods) {
+for (const method of ['runInThisContext', 'runInContext']) {
-  const child = spawn(process.execPath, [__filename, 'child', method], {
+  for (const listeners of [0, 1, 2]) {
-    stdio: [null, 'pipe', 'inherit', 'ipc']
+    const args = [__filename, 'child', method, listeners];
-  });
+    const child = spawn(process.execPath, args, {
-
+      stdio: [null, 'pipe', 'inherit', 'ipc']
-  child.on('message', common.mustCall(() => {
+    });
-    process.kill(child.pid, 'SIGINT');
+
-  }));
+    child.on('message', common.mustCall(() => {
-
+      process.kill(child.pid, 'SIGINT');
-  child.on('close', common.mustCall((code, signal) => {
+    }));
-    assert.strictEqual(signal, null);
+
-    assert.strictEqual(code, 0);
+    child.on('close', common.mustCall((code, signal) => {
-  }));
+      assert.strictEqual(signal, null);
+      assert.strictEqual(code, 0);
+    }));
+  }
 }