testing/lisp: Add missing `featurep' checks for required packages

* testing/lisp/test-ob-julia.el (featurep):
* testing/lisp/test-ob-ruby.el (featurep):
* testing/lisp/test-ob-scheme.el (featurep): Check for the required
external packages.

testing/lisp/test-ob-julia.el

@@ -24,6 +24,8 @@
 (require 'ob-core)
 (unless (featurep 'ob-julia)
   (signal 'missing-test-dependency "Support for julia code blocks"))
+(unless (featurep 'ess)
+  (signal 'missing-test-dependency "ESS"))
 
 (ert-deftest test-ob-julia/colnames-yes-header-argument ()
   (should

testing/lisp/test-ob-ruby.el

@@ -20,6 +20,8 @@
 (org-test-for-executable "ruby")
 (unless (featurep 'ob-ruby)
   (signal 'missing-test-dependency "Support for Ruby code blocks"))
+(unless (featurep 'inf-ruby)
+  (signal 'missing-test-dependency "inf-ruby"))
 
 (ert-deftest test-ob-ruby/session-output-1 ()
     (should (equal (org-test-with-temp-text "#+begin_src ruby :session org-test-ruby :results output

testing/lisp/test-ob-scheme.el

@@ -25,6 +25,8 @@
 
 (unless (featurep 'ob-scheme)
   (signal 'missing-test-dependency "Support for Scheme code blocks"))
+(unless (featurep 'geiser)
+  (signal 'missing-test-dependency "geiser"))
 
 (ert-deftest test-ob-scheme/tables ()
   "Test table output."