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+;;; do.el --- Small assertion library for Elisp -*- lexical-binding: t -*-
+;; Author: William Carroll <wpcarro@gmail.com>
+
+;;; Commentary:
+;; Assertion library inspired by Elixir's core testing library.
+;;
+;; The goal here is to create this module without relying on other non-core
+;; Elisp libraries.  I will attempt to do this as long as I'm not sacrificing
+;; the readability of this code nor the ease at which it can be written.
+;;
+;; A note on testing:
+;; Another goal with this library is to blur the line between testing code and
+;; runtime code.  Developers should ideally be using `do/assert' and `do/refute'
+;; in their library code.  Because of this, I'm avoiding referring
+;; to the notion of testing in the names of these functions.
+;;
+;; Hypothesis:
+;; The lower the friction is for writing tests, the more likely people will
+;; write tests.
+
+;; TODO: Support better error messages, which might include information about
+;; line numbers in source code where the assertion failed.
+
+;; TODO: Consider offering the ability to have some of these functions compile
+;; to nothing at runtime if developers want to use them while developing without
+;; incurring the costs at runtime.
+
+;; TODO: Consider using this module instead of prelude.el.  Right now, I'm
+;; having troubling preferring one to the other.  The benefit of this module is
+;; that it's independent of prelude, but that might also be a downside, since
+;; the messaging that asserting should be a critical part of any core library
+;; like prelude.
+
+;;; Code:
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Library
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+(defmacro do/assert (x)
+  "Errors unless X is t.
+These are strict assertions and purposely do not rely on truthiness."
+  (let ((as-string (format "%s" x)))
+    `(unless (equal t ,x)
+       (error (concat "Assertion failed: " ,as-string)))))
+
+(defmacro do/refute (x)
+  "Errors unless X is nil."
+  (let ((as-string (format "%s" x)))
+    `(unless (eq nil ,x)
+       (error (concat "Refutation failed: " ,as-string)))))
+
+(provide 'do)
+;;; do.el ends here