diff --git a/sextant-tests.lisp b/sextant-tests.lisp
index 0b5e223..c557243 100644
--- a/sextant-tests.lisp
+++ b/sextant-tests.lisp
@@ -2,3 +2,43 @@
 (ql:quickload :fiveam)
 
 (use-package :fiveam)
+(use-package :editor)
+
+(def-suite all-tests)
+
+(def-suite gap-buffer :in all-tests)
+(in-suite gap-buffer)
+
+(defparameter gb (make-gap-buffer "abcdefghijklmnopqrstuvwxyz"))
+(test make-gap-buffer
+      (is (equal "#S(GAP-BUFFER \"abcdefghijklmnopqrstuvwxyz[26-90(64)]\")" (gap-buffer-print gb))))
+
+(test move-gap
+      (is (equal "#S(GAP-BUFFER \"abcdefghijklmno[15-79(64)]pqrstuvwxyz\")" (gap-buffer-print (gap-buffer-move-gap gb 15))))
+      (is (equal "#S(GAP-BUFFER \"ab[2-66(64)]cdefghijklmnopqrstuvwxyz\")" (gap-buffer-print (gap-buffer-move-gap gb 2)))))
+
+(test insert-string
+      (is (equal "#S(GAP-BUFFER \"ab123456789[11-66(55)]cdefghijklmnopqrstuvwxyz\")" (gap-buffer-print (gap-buffer-insert-string gb "123456789"))))
+      (is (equal "#S(GAP-BUFFER \"ab123456789pyfgcrlaoeuidhtns[28-66(38)]cdefghijklmnopqrstuvwxyz\")" (gap-buffer-print (gap-buffer-insert-string gb "pyfgcrlaoeuidhtns"))))
+      (is (equal "#S(GAP-BUFFER \"ab123456789pyfgcrlaoeuidhtns;qjkxbmwvzlrcgpoaeusnth[51-66(15)]cdefghijklmnopqrstuvwxyz\")" (gap-buffer-print (gap-buffer-insert-string gb ";qjkxbmwvzlrcgpoaeusnth"))))
+      (is (equal "#S(GAP-BUFFER \"ab123456789pyfgcrlaoeuidhtns;qjkxbmwvzlrcgpoaeusnth0123456789[61-66(5)]cdefghijklmnopqrstuvwxyz\")" (gap-buffer-print (gap-buffer-insert-string gb "0123456789")))))
+
+(test grow-gap
+      (is (equal "#S(GAP-BUFFER \"ab123456789pyfgcrlaoeuidhtns;qjkxbmwvzlrcgpoaeusnth01234567899876543210abcdefghij[81-145(64)]cdefghijklmnopqrstuvwxyz\")" (gap-buffer-print (gap-buffer-insert-string gb "9876543210abcdefghij")))))
+
+(test delete
+      (is (equal "#S(GAP-BUFFER \"ab123456789pyfgcrlaoeuidhtns;qjkxbmwvzlrcgpoaeusnth01234567899876543210abcdefghij[81-148(67)]fghijklmnopqrstuvwxyz\")" (gap-buffer-print (gap-buffer-delete gb 3 :after))))
+      (is (equal "#S(GAP-BUFFER \"ab123456789pyfgcrlaoeuidhtns;qjkxbmwvzlrcgpoaeusnth01234567899876543210abcdefghij[81-169(88)]\")" (gap-buffer-print (gap-buffer-delete gb 23 :after))))
+      (is (equal "#S(GAP-BUFFER \"ab123456789pyfgcrlaoeuidhtns;qjkxbmwvzlrcgpoaeusnth01234567899876543210abcdefghij[81-169(88)]\")" (gap-buffer-print (gap-buffer-delete gb 23 :after))))
+      (is (equal "#S(GAP-BUFFER \"ab123456789pyfgcrlaoeuidhtns;qjkxbmwvzlrcgpoaeusnth0123456[58-169(111)]\")" (gap-buffer-print (gap-buffer-delete gb 23))))
+      (is (equal "#S(GAP-BUFFER \"ab123456789pyfgcrlaoeuidhtns;qjkxbm[35-169(134)]\")" (gap-buffer-print (gap-buffer-delete gb 23))))
+      (is (equal "#S(GAP-BUFFER \"ab123456789p[12-169(157)]\")" (gap-buffer-print (gap-buffer-delete gb 23))))
+      (is (equal "#S(GAP-BUFFER \"[0-169(169)]\")" (gap-buffer-print (gap-buffer-delete gb 23)))))
+
+(test insert-string-move-gap
+      (is (equal "#S(GAP-BUFFER \"abcdefghijklmnopqrstuvwxyz[26-169(143)]\")" (gap-buffer-print (gap-buffer-insert-string gb "abcdefghijklmnopqrstuvwxyz"))))
+      (is (equal "#S(GAP-BUFFER \"[0-143(143)]abcdefghijklmnopqrstuvwxyz\")" (gap-buffer-print (gap-buffer-move-gap gb 0))))
+      (is (equal "#S(GAP-BUFFER \"0123456789[10-143(133)]abcdefghijklmnopqrstuvwxyz\")" (gap-buffer-print (gap-buffer-insert-string gb "0123456789"))))
+      (is (equal "#S(GAP-BUFFER \"0123456789abcdefghijklmnopqrstuvwxyz[36-169(133)]\")" (gap-buffer-print (gap-buffer-move-gap gb 200)))))
+
+(run! 'all-tests)