test: Fix tests that check the *Completions* buffer.

Before this change, tests that check the *Completions* buffer relied on
text whose wording has changed across versions. This change checks the
buffer in a way that will hopefully not be so version-specific.

Author: szermatt

test/turtles-instance-test.el

@@ -230,12 +230,11 @@
      ;; Make sure that the short documentation are provided correctly as annotations.
      (minibuffer-complete)
      (turtles-with-grab-buffer (:buf "*Completions*")
-       (goto-char (point-min))
-       (search-forward "possible completions:\n")
-       (delete-region (point-min) (point))
+       (goto-char (point-max))
+       (forward-line -1)
        (should (equal (concat "default Emacs instance to run tests on.\n"
                               "turtles--restart A private test instance to test restart.")
-                      (buffer-string))))
+                      (buffer-substring (point) (point-max)))))
 
      ;; Select restart
      (execute-kbd-macro "turtles--restart"))))

test/turtles-test.el

@@ -1096,8 +1096,8 @@
       (minibuffer-complete)
       (minibuffer-complete)
       (turtles-with-grab-buffer (:buf "*Completions*")
-        (goto-char (point-min))
-        (search-forward "possible completions:\n")
+        (goto-char (point-max))
+        (forward-line -1)
         (should (equal (concat "copy Display a copy of the instance buffer.\n"
                                "embedded Display buffer in the terminal buffer.")
                        (buffer-substring (point) (point-max))))
@@ -1145,8 +1145,8 @@
       (minibuffer-complete)
       (minibuffer-complete)
       (turtles-with-grab-buffer (:buf "*Completions*")
-        (goto-char (point-min))
-        (search-forward "possible completions:\n")
+        (goto-char (point-max))
+        (forward-line -1)
         (should (equal (concat "lambda-1 My Lambda 1.\n"
                                "lambda-2 My Lambda 2.")
                        (buffer-substring (point) (point-max)))))