diff --git a/tests/self-edit-tests.lisp b/tests/self-edit-tests.lisp
new file mode 100644
index 0000000..150e746
--- /dev/null
+++ b/tests/self-edit-tests.lisp
@@ -0,0 +1,81 @@
+(defpackage :opencortex-self-edit-tests
+  (:use :cl :fiveam :opencortex)
+  (:export #:self-edit-suite))
+
+(in-package :opencortex-self-edit-tests)
+
+(def-suite self-edit-suite
+  :description "Tests for Self-Edit skill.")
+
+(in-suite self-edit-suite)
+
+(test balance-parens-balanced
+  (let ((result (opencortex::self-edit-balance-parens "(+ 1 2)")))
+    (is (string= result "(+ 1 2)"))
+    (is (not (null (read-from-string result))))))
+
+(test balance-parens-missing-open
+  (let ((result (opencortex::self-edit-balance-parens "+ 1 2)")))
+    (is (string= result "(+ 1 2)"))
+    (is (not (null (read-from-string result))))))
+
+(test balance-parens-missing-close
+  (let ((result (opencortex::self-edit-balance-parens "(+ 1 2")))
+    (is (string= result "(+ 1 2)"))
+    (is (not (null (read-from-string result))))))
+
+(test balance-parens-deep
+  (let ((result (opencortex::self-edit-balance-parens "((lambda (x) (if x (+ 1 2) 3))")))
+    (is (string= result "((lambda (x) (if x (+ 1 2) 3)))"))
+    (is (not (null (read-from-string result))))))
+
+(test balance-parens-empty
+  (let ((result (opencortex::self-edit-balance-parens "")))
+    (is (string= result ""))))
+
+(test test-self-edit-apply-success
+  "Verify self-edit-apply performs surgical replacement correctly."
+  (let ((test-file "/tmp/self-edit-test.lisp"))
+    (unwind-protect
+        (progn
+          (with-open-file (out test-file :direction :output :if-exists :supersede)
+            (write-string "(defun hello () (format t \"world~%\"))" out))
+          (let ((result (opencortex::self-edit-apply test-file "world" "universe")))
+            (is (eq (getf result :status) :success))
+            (let ((content (uiop:read-file-string test-file)))
+              (is (search "universe" content))
+              (is (not (search "world" content))))))
+      (uiop:delete-file-if-exists test-file))))
+
+(test test-self-edit-apply-not-found
+  "Verify self-edit-apply returns error when pattern not found."
+  (let ((test-file "/tmp/self-edit-test2.lisp"))
+    (unwind-protect
+        (progn
+          (with-open-file (out test-file :direction :output :if-exists :supersede)
+            (write-string "(defun hello () t)" out))
+          (let ((result (opencortex::self-edit-apply test-file "nonexistent-pattern" "new")))
+            (is (eq (getf result :status) :error))
+            (is (search "not found" (getf result :message)))))
+      (uiop:delete-file-if-exists test-file))))
+
+(test test-self-edit-apply-file-not-found
+  "Verify self-edit-apply returns error when file does not exist."
+  (let ((result (opencortex::self-edit-apply "/nonexistent/path/file.lisp" "old" "new")))
+    (is (eq (getf result :status) :error))
+    (is (search "not found" (getf result :message)))))
+
+(test test-self-edit-parse-location-from-payload
+  "Verify self-edit-parse-location extracts file/line from payload."
+  (let ((context '(:payload (:file "/tmp/test.lisp" :line 42 :message "error"))))
+    (let ((result (opencortex::self-edit-parse-location context)))
+      (is (equal "/tmp/test.lisp" (getf result :file)))
+      (is (eq 42 (getf result :line))))))
+
+(test test-self-edit-parse-location-from-message
+  "Verify self-edit-parse-location extracts file/line from error message."
+  (let ((context '(:payload (:message "Error in /home/user/project/foo.lisp at line 99"))))
+    (let ((result (opencortex::self-edit-parse-location context)))
+      (is (search "foo.lisp" (getf result :file)))
+      (is (eq 99 (getf result :line))))))
+)