Improve ert-test-erts-file documentation

* lisp/emacs-lisp/ert.el (ert-test-erts-file): Improve docstring.
* doc/misc/ert.texi (erts files): Fix typo.

2 files changed, 9 insertions, 3 deletions

diff --git a/doc/misc/ert.texi b/doc/misc/ert.texi
index 4dccd8edcf0..1b7f38daadf 100644
--- a/doc/misc/ert.texi
+++ b/doc/misc/ert.texi
@@ -822,7 +822,7 @@ that's pretty difficult to read and write, especially when the text in
 question is multi-line.
 
 So ert provides a function called @code{ert-test-erts-file} that takes
-two parameters: The name of a specially-formatted @dfn{erts} file, and
+two parameters: the name of a specially-formatted @dfn{erts} file, and
 (optionally) a function that performs the transform.
 
 @findex erts-mode
diff --git a/lisp/emacs-lisp/ert.el b/lisp/emacs-lisp/ert.el
index 21bee4c6d8b..49b54c2d00f 100644
--- a/lisp/emacs-lisp/ert.el
+++ b/lisp/emacs-lisp/ert.el
@@ -2880,8 +2880,14 @@ To be used in the ERT results buffer."
   nil)
 
 (defun ert-test-erts-file (file &optional transform)
-  "Parse FILE as a file containing before/after parts.
-TRANSFORM will be called to get from before to after."
+  "Parse FILE as a file containing before/after parts (an erts file).
+
+This function puts the \"before\" section of an .erts file into a
+temporary buffer, calls the TRANSFORM function, and then compares
+the result with the \"after\" section.
+
+See Info node `(ert) erts files' for more information on how to
+write erts files."
   (with-temp-buffer
     (insert-file-contents file)
     (let ((gen-specs (list (cons 'dummy t)