Move unit tests from ert to buttercup

Easier to organize and write. Now I can hopefully strive for better
coverage!

core/core-tests.el

@@ -0,0 +1,68 @@
+;;; core/core-tests.el -*- lexical-binding: t; -*-
+
+(defun doom//run-tests (&optional modules)
+  "Run all loaded tests, specified by MODULES (a list of module cons cells) or
+command line args following a double dash (each arg should be in the
+'module/submodule' format).
+
+If neither is available, run all tests in all enabled modules."
+  (interactive)
+  (let (noninteractive)
+    ;; Core libraries aren't fully loaded in a noninteractive session, so we
+    ;; reload it with `noninteractive' set to nil to force them to.
+    (quiet! (doom//reload-autoloads))
+    (doom-initialize t))
+  (let ((target-paths
+         ;; Convert targets into a list of string paths, pointing to the root
+         ;; directory of modules
+         (cond ((stringp (car modules)) ; command line
+                (save-match-data
+                  (cl-loop for arg in modules
+                           if (string= arg ":core") collect doom-core-dir
+                           else if (string-match-p "/" arg)
+                           nconc (mapcar (apply-partially #'expand-file-name arg)
+                                         doom-modules-dirs)
+                           else
+                           nconc (cl-loop for dir in doom-modules-dirs
+                                          for path = (expand-file-name arg dir)
+                                          if (file-directory-p path)
+                                          nconc
+                                          (doom-files-in
+                                           path :type 'dirs :depth 1 :full t))
+                           finally do (setq argv nil))))
+
+               (modules ; cons-cells given to MODULES
+                (cl-loop for (module . submodule) in modules
+                         if (doom-module-locate-path module submodule)
+                         collect it))
+
+               ((append (list doom-core-dir)
+                        (doom-module-load-path))))))
+    ;; Load all the unit test files...
+    (require 'buttercup)
+    (mapc (lambda (file) (load file :noerror (not doom-debug-mode)))
+          (doom-files-in (mapcar (apply-partially #'expand-file-name "test/")
+                                 target-paths)
+                         :match "\\.el$" :full t))
+    ;; ... then run them
+    (when doom-debug-mode
+      (setq buttercup-stack-frame-style 'pretty))
+    (let ((split-width-threshold 0)
+          (split-height-threshold 0)
+          (window-min-width 0)
+          (window-min-height 0))
+      (buttercup-run))))
+
+
+;;
+(defmacro def-test! (_name &rest _body))
+
+(defmacro insert! (&rest text)
+  "Insert TEXT in buffer, then move cursor to last {0} marker."
+  `(progn
+     (insert ,@text)
+     (when (search-backward "{0}" nil t)
+       (replace-match "" t t))))
+
+(provide 'core-tests)
+;;; core-tests.el ends here