test: increase coverage for stream writable

Refs: nodejs#41433 (comment)

PR-URL: nodejs#41486
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>

test/parallel/test-stream-writable-final-throw.js

@@ -0,0 +1,23 @@
+'use strict';
+
+const common = require('../common');
+const {
+  Duplex,
+} = require('stream');
+
+{
+  class Foo extends Duplex {
+    _final(callback) {
+      throw new Error('fhqwhgads');
+    }
+
+    _read() {}
+  }
+
+  const foo = new Foo();
+  foo._write = common.mustCall((chunk, encoding, cb) => {
+    cb();
+  });
+  foo.end('test', common.expectsError({ message: 'fhqwhgads' }));
+  foo.on('error', common.mustCall());
+}