Three Emacs Commands

Three commands I wish I knew sooner to write emacs-lisp.

• toggle-debug-on-error: I enable it when a plugin or my own code is throwing an error. The stack trace makes it easy to find the root cause of the problem.
• ielm: launch it, and combine it with ielm-change-working-buffer and ielm-display-working-buffer. Makes it a dream to write extensions.
• ert: built-in unit tester. I write specs as part of my config. They are load automatically. I run them with ert. You can select t to run everything or pick a particular test. The result window also has nice keybindings like r to rerun and . to jump to the failing spec.