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Diffstat (limited to 'languages')
| -rw-r--r-- | languages/elisp/claude/rules/elisp-testing.md | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/languages/elisp/claude/rules/elisp-testing.md b/languages/elisp/claude/rules/elisp-testing.md index 3883902..b5def78 100644 --- a/languages/elisp/claude/rules/elisp-testing.md +++ b/languages/elisp/claude/rules/elisp-testing.md @@ -43,6 +43,32 @@ Write the failing test first. A failing test proves you understand the change. A For untested code, write a **characterization test** that captures current behavior before you change anything. It becomes the safety net for the refactor. +## Interactive vs Internal — Split for Testability + +When a function mixes business logic with user interaction, split it: + +- **Internal** (`cj/--foo`) — pure logic. All parameters explicit. No prompts, + no UI. Deterministic and trivially testable. +- **Interactive wrapper** (`cj/foo`) — thin layer that reads user input and + delegates to the internal. + +```elisp +(defun cj/--move-buffer-and-file (dir &optional ok-if-exists) + "Move the current buffer's file into DIR. Overwrite if OK-IF-EXISTS." + ...) + +(defun cj/move-buffer-and-file () + "Interactive wrapper: prompt for DIR, delegate." + (interactive) + (let ((dir (read-directory-name "Move to: "))) + (cj/--move-buffer-and-file dir))) +``` + +Test the internal directly with parameter values — no `cl-letf` on +`read-directory-name`, `yes-or-no-p`, etc. The wrapper gets a smoke test or +nothing — Emacs already tests its own prompts. The internal also becomes +reusable by other Elisp code without triggering UI. + ## Mocking Mock at boundaries: |