From f55711aefc18f6707773a40a859baf874a6bbe6d Mon Sep 17 00:00:00 2001
From: Mats Lidell <mats.lidell@lidells.se>
Date: Thu, 26 Mar 2026 22:38:00 +0100
Subject: [PATCH] Add kotl-mode:kill-tree test

* test/kotl-mode-tests.el (kotl-mode--kill-tree-first-and-only-tree):
    Verify change works.

* test/kotl-mode-tests.el (kotl-mode-split-cell): Use
    new kotl-mode:kill-tree with arg 0 for clearer reuse of test buffer.
    (kotl-mode--kill-tree-erase-buffer): Test buffer can be erased.
---
 ChangeLog               |  8 ++++++++
 test/kotl-mode-tests.el | 33 +++++++++++++++++++++++++++++++--
 2 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 392caccc..a4ef3361 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2026-03-30  Mats Lidell  <matsl@gnu.org>
+
+* test/kotl-mode-tests.el (kotl-mode-split-cell): Use kotl-mode:kill-tree
+    with new arg 0 for clearer reuse of test buffer.
+    (kotl-mode--kill-tree-erase-buffer): Add test for arg 0 to erase buffer.
+    (kotl-mode--kill-tree-first-and-only-tree): Add test for verifying
+    removing one tree.
+
 2026-03-29  Bob Weiner  <rsw@gnu.org>
 
 * hypb.el (hypb:in-string-cache): Move Private Variable definitions to precede
diff --git a/test/kotl-mode-tests.el b/test/kotl-mode-tests.el
index 81665be4..322c9f6d 100644
--- a/test/kotl-mode-tests.el
+++ b/test/kotl-mode-tests.el
@@ -430,6 +430,35 @@
           (should (string= (kcell-view:idstamp) "03")))
       (hy-delete-file-and-buffer kotl-file))))
 
+(ert-deftest kotl-mode--kill-tree-first-and-only-tree ()
+  "Verify removing a one cell tree creates an initial empty first cell."
+  (let ((kotl-file (make-temp-file "hypb" nil ".kotl")))
+    (unwind-protect
+        (with-current-buffer (find-file kotl-file)
+          (insert "first")
+          (kotl-mode:add-child 1 "second")
+          (kotl-mode:beginning-of-buffer)
+          (kotl-mode:kill-tree)
+          (should (kotl-mode:first-cell-p))
+          (should (string-empty-p (kcell-view:contents))))
+      (hy-delete-file-and-buffer kotl-file))))
+
+(ert-deftest kotl-mode--kill-tree-erase-buffer ()
+  "Verify buffer is erased leaving just the initial empty first cell."
+  (with-temp-buffer
+    (kotl-mode)
+    (kotl-mode:kill-tree 0)
+    (kotl-mode:end-of-buffer)
+    (should (kotl-mode:first-cell-p))
+    (should (string-empty-p (kcell-view:contents)))
+
+    (dotimes (i 20)
+      (kotl-mode:add-cell 1 "contents"))
+    (kotl-mode:kill-tree 0)
+    (kotl-mode:end-of-buffer)
+    (should (kotl-mode:first-cell-p))
+    (should (string-empty-p (kcell-view:contents)))))
+
 (ert-deftest kotl-mode-split-cell ()
   "Kotl-mode split cell."
   :expected-result :failed
@@ -445,7 +474,7 @@
             (should (string= (kcell-view:label (point)) "1a"))
             (should (string= (kcell-view:idstamp) "02")))
           (ert-info ("Split after first line")
-            (kotl-mode:kill-tree)
+            (kotl-mode:kill-tree 0)
             (insert "first")
             (kotl-mode:newline 1)
             (insert "second")
@@ -454,7 +483,7 @@
             (kotl-mode:split-cell)
             (should (= (line-number-at-pos) 3)))
           (ert-info ("Split before second line")
-            (kotl-mode:kill-tree)
+            (kotl-mode:kill-tree 0)
             (insert "first")
             (kotl-mode:newline 1)
             (insert "second")