test: add test for debugging one line files

This commit adds a regression test for debugging of
single line files.

Refs: nodejs#4297
PR-URL: nodejs#4298
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Ali Ijaz Sheikh <ofrobots@google.com>

test/fixtures/exports-function-with-param.js

@@ -0,0 +1 @@
+module.exports = function foo(arg) { return arg; }

test/parallel/test-vm-debug-context.js

@@ -53,6 +53,24 @@ assert.strictEqual(vm.runInDebugContext(undefined), undefined);
   assert.equal(breaks, 1);
 })();
 
+// Can set listeners and breakpoints on a single line file
+(function() {
+  const Debug = vm.runInDebugContext('Debug');
+  const fn = require(common.fixturesDir + '/exports-function-with-param');
+  let called = false;
+
+  Debug.setListener(function(event, state, data) {
+    if (data.constructor.name === 'BreakEvent') {
+      called = true;
+    }
+  });
+
+  Debug.setBreakPoint(fn);
+  fn('foo');
+  assert.strictEqual(Debug.showBreakPoints(fn), '(arg) { [B0]return arg; }');
+  assert.strictEqual(called, true);
+})();
+
 // See https://github.com/nodejs/node/issues/1190, fatal errors should not
 // crash the process.
 var script = common.fixturesDir + '/vm-run-in-debug-context.js';