It can be difficult to diagnose test failures in the Eshell ERT test 
suite, since it doesn't print useful details like the command that was 
executed. See bug#57129 for example.

Here are some patches to fix that. The failures now look like this:

----------------------------------------

     (ert-test-failed
      ((should
        (eshell-match-output regexp))
       :form
       (eshell-match-output "wrong")
       :value nil :explanation
       (mismatched-output
        (command "echo $INSIDE_EMACS[, 1]\n")
        (output "eshell\n")
        (regexp "wrong"))))

----------------------------------------

     (ert-test-failed
      ((should
        (eshell-command-result--equal command
                                      (eshell-test-command-result command)
                                      result))
       :form
       (eshell-command-result--equal "echo $LINES" 22 2)
       :value nil :explanation
       (nonequal-result
        (command "echo $LINES")
        (result 22)
        (expected 2))))

----------------------------------------

Most of the first two patches are purely-mechanical changes to update 
function calls. The diffs ended up being pretty big, but I think it 
improves matters. Let me know if I should do it differently (especially 
for the commit message; I didn't see much benefit to listing *every* 
test function I touched, but maybe I should do that?)

While I was testing these, I also found a couple real bugs with the 
'eshell-command-result' function. This throws 'eshell-defer':

   M-: (eshell-command-result "if {[ foo = foo ]} {echo hi}")

That's because 'eshell-do-eval' wasn't forwarding the SYNCHRONOUS-P 
argument in a couple spots.

This is also wrong:

   M-: (eshell-command-result "if (zerop 1) {echo yes} {echo no}")
     => nil

It should return "no".

I fixed these in the third patch. Maybe that could go in a separate bug, 
but it's fairly closely related to this one.