2 files changed, 37 insertions, 2 deletions

diff --git a/modules/lorem-optimum.el b/modules/lorem-optimum.el
index 8aa96345..14f1d666 100644
--- a/modules/lorem-optimum.el
+++ b/modules/lorem-optimum.el
@@ -219,8 +219,22 @@ Builds and caches the keys list lazily if not already cached."
   (message "Lorem-optimum learned from file: %s" file))
 
 (defun cj/lipsum (n)
-  "Return N words of lorem ipsum."
-  (cj/markov-generate cj/lipsum-chain n '("Lorem" "ipsum")))
+  "Return N words of lorem ipsum.
+Interactively, prompt for N and echo the generated words.
+
+Signal a `user-error' when the Markov chain is empty (for example when the
+training file `cj/lipsum-default-file' is missing).  Without this, callers
+such as `cj/lipsum-insert' would insert nil and raise a cryptic wrong-type
+error far from the cause.  Train the chain with `cj/lipsum-learn-file',
+`cj/lipsum-learn-buffer', or `cj/lipsum-learn-region', or restore the file."
+  (interactive "nNumber of words: ")
+  (let ((text (cj/markov-generate cj/lipsum-chain n '("Lorem" "ipsum"))))
+    (unless (and (stringp text) (not (string-empty-p text)))
+      (user-error "Lorem-optimum chain is empty; train it with cj/lipsum-learn-file or restore %s"
+                  cj/lipsum-default-file))
+    (when (called-interactively-p 'any)
+      (message "%s" text))
+    text))
 
 (defun cj/lipsum-insert (n)
   "Insert N words of lorem ipsum at point."
diff --git a/tests/test-lorem-optimum.el b/tests/test-lorem-optimum.el
index f928c972..b7d97a8e 100644
--- a/tests/test-lorem-optimum.el
+++ b/tests/test-lorem-optimum.el
@@ -253,5 +253,26 @@ an empty string, not an error."
   (let ((cj/lipsum-chain (cj/markov-chain-create)))
     (should (equal "" (cj/lipsum-title)))))
 
+;;; cj/lipsum entry point
+
+(ert-deftest test-lipsum-returns-string-with-populated-chain ()
+  "Normal: cj/lipsum returns a non-empty string when the chain is trained."
+  (let ((cj/lipsum-chain
+         (test-learn "Lorem ipsum dolor sit amet consectetur adipiscing elit")))
+    (let ((result (cj/lipsum 5)))
+      (should (stringp result))
+      (should (> (length result) 0)))))
+
+(ert-deftest test-lipsum-empty-chain-signals-user-error ()
+  "Error: cj/lipsum on an empty chain signals a user-error naming the fix,
+rather than returning nil and letting cj/lipsum-insert do (insert nil),
+which raises a cryptic wrong-type error far from the cause."
+  (let ((cj/lipsum-chain (cj/markov-chain-create)))
+    (should-error (cj/lipsum 5) :type 'user-error)))
+
+(ert-deftest test-lipsum-is-interactive-command ()
+  "Normal: cj/lipsum is a command, as its Commentary (M-x cj/lipsum) advertises."
+  (should (commandp 'cj/lipsum)))
+
 (provide 'test-lorem-optimum)
 ;;; test-lorem-optimum.el ends here