Tests involving post-command-hook

[Stephen Berman]

I'm using ERT to test for the hl-line face property and it appears that
in the test environment, the function hl-line-highlight is not
automatically run from post-command-hook as it should be, although I use
call-interactively to mimic a command invocation.  It works only if I
explicitly call run-hooks.  I also see this without ERT:

(let ((buf (get-buffer-create "*hl-line-test*")))
  (with-current-buffer buf
    (erase-buffer)
    (insert "This is a test.\n")
    (hl-line-mode)
    (call-interactively (lambda () (interactive) (forward-line -1)))
    ;; (run-hooks 'post-command-hook)
    (if (eq 'hl-line (get-char-property (point) 'face))
        (message "test1 passed")
      (message "test1 failed"))
    (hl-line-mode -1)
    (erase-buffer)
    (insert "This is a test.\n")
    (call-interactively (lambda () (interactive) (forward-line -1)))
    (hl-line-mode)
    (if (eq 'hl-line (get-char-property (point) 'face))
        (message "test2 passed")
      (message "test2 failed"))
    (hl-line-mode -1)
    (erase-buffer)
    (insert "This is line 1.\nThis is line 2.\n")
    (call-interactively (lambda () (interactive) (forward-line -1)))
    (hl-line-mode)
    (if (eq 'hl-line (get-char-property (point) 'face))
        (message "test3.1 passed")
      (message "test3.1 failed"))
    (call-interactively (lambda () (interactive) (forward-line -1)))
    ;; (run-hooks 'post-command-hook)
    (if (eq 'hl-line (get-char-property (point) 'face))
        (message "test3.2 passed")
      (message "test3.2 failed")))
    (hl-line-mode -1))

Evaluating this in emacs -Q or loading it with emacs --batch yields
this:

test1 failed
test2 passed
test3.1 passed
test3.2 failed

The two successful tests are because hl-line-mode calls
hl-line-highlight before adding it to post-command-hook.  Uncommenting
the two (run-hooks 'post-command-hook) lines yields this, which is what
I expected without run-hooks (and what I see when testing without them
interactively):

test1 passed
test2 passed
test3.1 passed
test3.2 passed

Is this behavior of post-command-hook expected and if so, is using
run-hooks in ERT valid, i.e. is it still really testing hl-line-mode
behavior?

Steve Berman