Improve tests/organization for built-in variables

* lisp/eshell/em-dirs.el (eshell-inside-emacs)
(eshell-dirs-initialize): Move 'INSIDE_EMACS' from here...

* lisp/eshell/esh-var.el (eshell-inside-emacs)
(eshell-variable-aliases-alist): ... to here, and improve doc string.

* test/lisp/eshell/eshell-tests.el (eshell-test/inside-emacs-var):
Move from here...

* test/lisp/eshell/esh-var-tests.el (esh-var-test/inside-emacs-var):
... to here.
(esh-var-test/last-arg-var-indices)
(esh-var-test/last-arg-var-split-indices): New tests.

* test/lisp/eshell/em-alias-tests.el:
* test/lisp/eshell/em-dirs-tests.el:
* test/lisp/eshell-em-script-tests.el: New files.

* doc/misc/eshell.texi (Built-ins): Fix 'cd' documentation; it works
with the directory ring, not the directory stack.  Move built-in
variables documentation from here...
(Variables): ... to here, and add documentation for missing built-in
variables.

1 files changed, 72 insertions, 0 deletions

diff --git a/test/lisp/eshell/em-dirs-tests.el b/test/lisp/eshell/em-dirs-tests.el
new file mode 100644
index 00000000000..eb27acd208e
--- /dev/null
+++ b/test/lisp/eshell/em-dirs-tests.el
@@ -0,0 +1,72 @@
+;;; em-dirs-tests.el --- em-dirs test suite  -*- lexical-binding:t -*-
+
+;; Copyright (C) 2022 Free Software Foundation, Inc.
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; Tests for Eshell's dirs module.
+
+;;; Code:
+
+(require 'ert)
+(require 'esh-mode)
+(require 'eshell)
+(require 'em-dirs)
+
+(require 'eshell-tests-helpers
+         (expand-file-name "eshell-tests-helpers"
+                           (file-name-directory (or load-file-name
+                                                    default-directory))))
+;;; Tests:
+
+(ert-deftest em-dirs-test/pwd-var ()
+  "Test using the $PWD variable."
+  (should (equal (eshell-test-command-result "echo $PWD")
+                 (expand-file-name (eshell/pwd)))))
+
+(ert-deftest em-dirs-test/short-pwd-var ()
+  "Test using the $+ (current directory) variable."
+  (should (equal (eshell-test-command-result "echo $+")
+                 (expand-file-name (eshell/pwd)))))
+
+(ert-deftest em-dirs-test/oldpwd-var ()
+  "Test using the $OLDPWD variable."
+  (let (eshell-last-dir-ring-file-name)
+    (with-temp-eshell
+     (eshell-command-result-p "echo $OLDPWD"
+                              "\\`\\'")
+     (ring-insert eshell-last-dir-ring "/some/path")
+     (eshell-command-result-p "echo $OLDPWD"
+                              "/some/path\n"))))
+
+(ert-deftest em-dirs-test/directory-ring-var ()
+  "Test using the $- (directory ring) variable."
+  (let (eshell-last-dir-ring-file-name)
+    (with-temp-eshell
+     (eshell-command-result-p "echo $-"
+                              "\\`\\'")
+     (ring-insert eshell-last-dir-ring "/some/path")
+     (ring-insert eshell-last-dir-ring "/other/path")
+     (eshell-command-result-p "echo $-"
+                              "/other/path\n")
+     (eshell-command-result-p "echo $-[0]"
+                              "/other/path\n")
+     (eshell-command-result-p "echo $-[1]"
+                              "/some/path\n"))))
+
+;; em-dirs-tests.el ends here