diff --git a/site-lisp/timeline-tools-test.el b/site-lisp/timeline-tools-test.el
index 7acda9f..5cc7a9a 100644
--- a/site-lisp/timeline-tools-test.el
+++ b/site-lisp/timeline-tools-test.el
@@ -191,4 +191,144 @@ CLOCK: [2018-01-07 Sun 13:00]--[2018-01-11 Thu 13:33] => 96:33
 :END:
 ")))))
 
+(ert-deftest timeline-tools-test-add-clockline-to-marker-2 ()
+  "Test `timeline-tools-add-clockline-to-marker’ with running
+clock at same task."
+  (with-temp-buffer
+    (insert "
+* Task 1
+:LOGBOOK:
+CLOCK: [2018-01-10 Wed 10:07]--[2018-01-12 Fri 14:00] => 51:53
+CLOCK: [2018-01-08 Mon 16:15]--[2018-01-10 Wed 13:10] => 44:55
+CLOCK: [2018-01-07 Sun 13:15]--[2018-01-07 Sun 14:00] => 0:45
+:END:
+
+* Task 2
+:LOGBOOK:
+CLOCK: [2018-01-10 Wed 13:10]
+CLOCK: [2018-01-08 Mon 16:00]--[2018-01-08 Mon 16:15] =>  0:15
+CLOCK: [2018-01-07 Sun 15:13]--[2018-01-07 Sun 16:17] =>  1:04
+:END:
+")
+    (org-mode)
+    (let (;; simulate running clock at Task 2
+          (org-clock-hd-marker (progn (goto-char 216) (point-marker)))
+          (org-clock-marker (progn (goto-char 264) (point-marker)))
+          (org-clock-start-time (org-time-string-to-time "[2018-01-10 Wed 13:10]")))
+      (let ((result (timeline-tools-add-clockline-to-marker
+                     org-clock-hd-marker
+                     (org-time-string-to-seconds "[2018-01-07 Sun 13:00]")
+                     (org-time-string-to-seconds "[2018-01-11 Thu 13:33]"))))
+
+        (should (null result))
+        (should (equal org-clock-start-time
+                       (append (org-time-string-to-time "[2018-01-11 Thu 13:33]")
+                               '(0 0))))
+        (should (equal (buffer-string)
+                       "
+* Task 1
+:LOGBOOK:
+CLOCK: [2018-01-11 Thu 13:33]--[2018-01-12 Fri 14:00] => 24:27
+:END:
+
+* Task 2
+:LOGBOOK:
+CLOCK: [2018-01-11 Thu 13:33]
+CLOCK: [2018-01-07 Sun 13:00]--[2018-01-11 Thu 13:33] => 96:33
+:END:
+"))))))
+
+(ert-deftest timeline-tools-test-add-clockline-to-marker-3 ()
+  "Test `timeline-tools-add-clockline-to-marker’ with running
+clock at same task."
+  (with-temp-buffer
+    (insert "
+* Task 1
+:LOGBOOK:
+CLOCK: [2018-01-08 Mon 16:15]--[2018-01-10 Wed 13:10] => 44:55
+CLOCK: [2018-01-07 Sun 13:15]--[2018-01-07 Sun 14:00] => 0:45
+:END:
+
+* Task 2
+:LOGBOOK:
+CLOCK: [2018-01-10 Wed 13:10]
+CLOCK: [2018-01-08 Mon 16:00]--[2018-01-08 Mon 16:15] =>  0:15
+CLOCK: [2018-01-07 Sun 15:13]--[2018-01-07 Sun 16:17] =>  1:04
+:END:
+")
+    (org-mode)
+    (let (;; simulate running clock at Task 2
+          (org-clock-hd-marker (progn (goto-char 153) (point-marker)))
+          (org-clock-marker (progn (goto-char 201) (point-marker)))
+          (org-clock-start-time (org-time-string-to-time "[2018-01-10 Wed 13:10]")))
+      (let ((result (timeline-tools-add-clockline-to-marker
+                     (progn (goto-char 2) (point-marker))
+                     (org-time-string-to-seconds "[2018-01-07 Sun 13:00]")
+                     (org-time-string-to-seconds "[2018-01-11 Thu 13:33]"))))
+
+        (should (null result))
+        (should (equal org-clock-start-time
+                       (append (org-time-string-to-time "[2018-01-11 Thu 13:33]")
+                               '(0 0))))
+        (should (equal (buffer-string)
+                       "
+* Task 1
+:LOGBOOK:
+CLOCK: [2018-01-07 Sun 13:00]--[2018-01-11 Thu 13:33] => 96:33
+:END:
+
+* Task 2
+:LOGBOOK:
+CLOCK: [2018-01-11 Thu 13:33]
+:END:
+"))))))
+
+(ert-deftest timeline-tools-test-add-clockline-to-marker-4 ()
+  "Test `timeline-tools-add-clockline-to-marker’ with running
+clock at other task, and where afterwards only the running clock
+line is left."
+  (with-temp-buffer
+    (insert "
+* Task 1
+:LOGBOOK:
+CLOCK: [2018-01-10 Wed 10:07]--[2018-01-12 Fri 14:00] => 51:53
+CLOCK: [2018-01-08 Mon 16:15]--[2018-01-10 Wed 13:10] => 44:55
+CLOCK: [2018-01-07 Sun 13:15]--[2018-01-07 Sun 14:00] => 0:45
+:END:
+
+* Task 2
+:LOGBOOK:
+CLOCK: [2018-01-10 Wed 13:10]
+CLOCK: [2018-01-08 Mon 16:00]--[2018-01-08 Mon 16:15] =>  0:15
+CLOCK: [2018-01-07 Sun 15:13]--[2018-01-07 Sun 16:17] =>  1:04
+:END:
+")
+    (org-mode)
+    (let (;; simulate running clock at Task 2
+          (org-clock-hd-marker (progn (goto-char 216) (point-marker)))
+          (org-clock-marker (progn (goto-char 264) (point-marker)))
+          (org-clock-start-time (org-time-string-to-time "[2018-01-10 Wed 13:10]")))
+      (let ((result (timeline-tools-add-clockline-to-marker
+                     (progn (goto-char 2) (point-marker))
+                     (org-time-string-to-seconds "[2018-01-07 Sun 13:00]")
+                     (org-time-string-to-seconds "[2018-01-11 Thu 13:33]"))))
+
+        (should (null result))
+        (should (equal org-clock-start-time
+                       (append (org-time-string-to-time "[2018-01-11 Thu 13:33]")
+                               '(0 0))))
+        (should (equal (buffer-string)
+                       "
+* Task 1
+:LOGBOOK:
+CLOCK: [2018-01-07 Sun 13:00]--[2018-01-11 Thu 13:33] => 96:33
+CLOCK: [2018-01-11 Thu 13:33]--[2018-01-12 Fri 14:00] => 24:27
+:END:
+
+* Task 2
+:LOGBOOK:
+CLOCK: [2018-01-11 Thu 13:33]
+:END:
+"))))))
+
 ;; XXX: timeline-tools-add-clockline-to-marker (including updating current clock)