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+;;; test-custom-whitespace-delete-all.el --- Tests for cj/--delete-all-whitespace -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; Tests for the cj/--delete-all-whitespace function from custom-whitespace.el
+;;
+;; This function removes ALL whitespace characters from the region:
+;; spaces, tabs, newlines, and carriage returns. Useful for creating
+;; compact identifiers or removing all formatting.
+;;
+;; Uses the regexp [ \t\n\r]+ to match all whitespace.
+;;
+;; We test the NON-INTERACTIVE implementation (cj/--delete-all-whitespace)
+;; to avoid mocking region selection. This follows our testing best practice
+;; of separating business logic from UI interaction.
+
+;;; Code:
+
+(require 'ert)
+(require 'testutil-general)
+
+;; Add modules directory to load path
+(add-to-list 'load-path (expand-file-name "modules" user-emacs-directory))
+
+;; Stub dependencies before loading the module
+(defvar cj/custom-keymap (make-sparse-keymap)
+  "Stub keymap for testing.")
+
+;; Now load the actual production module
+(require 'custom-whitespace)
+
+;;; Test Helpers
+
+(defun test-delete-all-whitespace (input-text)
+  "Test cj/--delete-all-whitespace on INPUT-TEXT.
+Returns the buffer string after operation."
+  (with-temp-buffer
+    (insert input-text)
+    (cj/--delete-all-whitespace (point-min) (point-max))
+    (buffer-string)))
+
+;;; Normal Cases
+
+(ert-deftest test-delete-all-whitespace-single-space ()
+  "Should remove single space."
+  (let ((result (test-delete-all-whitespace "hello world")))
+    (should (string= result "helloworld"))))
+
+(ert-deftest test-delete-all-whitespace-multiple-spaces ()
+  "Should remove multiple spaces."
+  (let ((result (test-delete-all-whitespace "hello    world")))
+    (should (string= result "helloworld"))))
+
+(ert-deftest test-delete-all-whitespace-tabs ()
+  "Should remove tabs."
+  (let ((result (test-delete-all-whitespace "hello\tworld")))
+    (should (string= result "helloworld"))))
+
+(ert-deftest test-delete-all-whitespace-newlines ()
+  "Should remove newlines (joining lines)."
+  (let ((result (test-delete-all-whitespace "hello\nworld")))
+    (should (string= result "helloworld"))))
+
+(ert-deftest test-delete-all-whitespace-mixed ()
+  "Should remove all types of whitespace."
+  (let ((result (test-delete-all-whitespace "hello \t\n world")))
+    (should (string= result "helloworld"))))
+
+(ert-deftest test-delete-all-whitespace-multiple-words ()
+  "Should remove whitespace from multiple words."
+  (let ((result (test-delete-all-whitespace "one two three four")))
+    (should (string= result "onetwothreefour"))))
+
+(ert-deftest test-delete-all-whitespace-multiline ()
+  "Should remove all whitespace across multiple lines."
+  (let ((result (test-delete-all-whitespace "line1\nline2\nline3")))
+    (should (string= result "line1line2line3"))))
+
+(ert-deftest test-delete-all-whitespace-leading-trailing ()
+  "Should remove leading and trailing whitespace."
+  (let ((result (test-delete-all-whitespace "  hello world  ")))
+    (should (string= result "helloworld"))))
+
+(ert-deftest test-delete-all-whitespace-carriage-returns ()
+  "Should handle carriage returns."
+  (let ((result (test-delete-all-whitespace "hello\r\nworld")))
+    (should (string= result "helloworld"))))
+
+;;; Boundary Cases
+
+(ert-deftest test-delete-all-whitespace-empty-string ()
+  "Should handle empty string."
+  (let ((result (test-delete-all-whitespace "")))
+    (should (string= result ""))))
+
+(ert-deftest test-delete-all-whitespace-no-whitespace ()
+  "Should handle text with no whitespace (no-op)."
+  (let ((result (test-delete-all-whitespace "helloworld")))
+    (should (string= result "helloworld"))))
+
+(ert-deftest test-delete-all-whitespace-only-whitespace ()
+  "Should delete all content when only whitespace exists."
+  (let ((result (test-delete-all-whitespace "   \t   \n   ")))
+    (should (string= result ""))))
+
+(ert-deftest test-delete-all-whitespace-single-char ()
+  "Should handle single character with surrounding whitespace."
+  (let ((result (test-delete-all-whitespace "  x  ")))
+    (should (string= result "x"))))
+
+(ert-deftest test-delete-all-whitespace-very-long-text ()
+  "Should handle very long text."
+  (let ((result (test-delete-all-whitespace "word word word word word word word word")))
+    (should (string= result "wordwordwordwordwordwordwordword"))))
+
+(ert-deftest test-delete-all-whitespace-single-whitespace ()
+  "Should delete single whitespace character."
+  (let ((result (test-delete-all-whitespace " ")))
+    (should (string= result ""))))
+
+(ert-deftest test-delete-all-whitespace-consecutive-newlines ()
+  "Should remove all consecutive newlines."
+  (let ((result (test-delete-all-whitespace "hello\n\n\nworld")))
+    (should (string= result "helloworld"))))
+
+(ert-deftest test-delete-all-whitespace-complex-structure ()
+  "Should handle complex whitespace patterns."
+  (let ((result (test-delete-all-whitespace "  hello\n\t  world  \n  foo\t\tbar  ")))
+    (should (string= result "helloworldfoobar"))))
+
+;;; Error Cases
+
+(ert-deftest test-delete-all-whitespace-start-greater-than-end ()
+  "Should error when start > end."
+  (should-error
+   (with-temp-buffer
+     (insert "hello world")
+     (cj/--delete-all-whitespace (point-max) (point-min)))
+   :type 'error))
+
+(ert-deftest test-delete-all-whitespace-empty-region ()
+  "Should handle empty region (start == end) without error."
+  (with-temp-buffer
+    (insert "hello world")
+    (let ((pos (/ (+ (point-min) (point-max)) 2)))
+      (cj/--delete-all-whitespace pos pos)
+      ;; Should complete without error and not change buffer
+      (should (string= (buffer-string) "hello world")))))
+
+(provide 'test-custom-whitespace-delete-all)
+;;; test-custom-whitespace-delete-all.el ends here