test(prog): cover formatter wiring for python, go, shell, typescript

Four test files plus a shared testutil that locks in the formatter
bindings on C-; f across the four languages. Each test file checks:

- the format command is fboundp after the relevant package loads
- the C-; f binding resolves to that command (in the relevant
  mode-map, or in the buffer-local map for hook-based wiring)
- the underlying executable is on PATH (skipped via ert-skip if
  not installed)

No production change. The bindings were already at C-; f via two
mechanisms. Use-package :bind handles python and shell. The other
two install via local-set-key inside a hook. This regression net
catches silent breakage if any of those wirings get reshaped later.

The shared tests/testutil-format-wiring.el carries
format-test--ensure-packages-init, which calls package-initialize
once per batch run, since make test runs Emacs with --no-site-file
--no-site-lisp. Without it, use-package can't find blacken / shfmt
/ go-mode in elpa/. Also format-test--skip-unless-executable wraps
ert-skip with a clear "not on PATH" message so missing tools fail
informatively.

Per-language wiring inventory (no changes, just locked in):
- Python: blacken-buffer in python-ts-mode-map (use-package :bind)
- Shell: shfmt-buffer in sh-mode-map and bash-ts-mode-map
  (use-package :bind, gated on :if executable-find)
- Go: gofmt via cj/go-mode-keybindings hook
- TS/JS/Web: cj/webdev-format-buffer via cj/webdev-keybindings hook

13 tests across 4 files, all passing.

1 files changed, 40 insertions, 0 deletions

diff --git a/tests/test-prog-python--format-wiring.el b/tests/test-prog-python--format-wiring.el
new file mode 100644
index 00000000..67c18dd1
--- /dev/null
+++ b/tests/test-prog-python--format-wiring.el
@@ -0,0 +1,40 @@
+;;; test-prog-python--format-wiring.el --- Verify the Python formatter is wired -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; Three checks for the Python formatter:
+;;   1. `blacken-buffer' is fboundp after the prog-python config loads.
+;;   2. C-; f in `python-ts-mode-map' resolves to `blacken-buffer'.
+;;   3. The `black' executable is on PATH (skipped if not installed).
+
+;;; Code:
+
+(require 'ert)
+
+(add-to-list 'load-path (expand-file-name "modules" user-emacs-directory))
+(add-to-list 'load-path (expand-file-name "tests" user-emacs-directory))
+(require 'testutil-format-wiring)
+
+(format-test--ensure-packages-init)
+;; use-package's `:bind (:map ...)' defers until the named map exists.
+;; Loading python.el populates `python-ts-mode-map'; loading blacken
+;; resolves the binding form's late-binding hook.
+(ignore-errors (require 'prog-python))
+(require 'python)
+(require 'blacken)
+
+(ert-deftest test-prog-python-format-command-fboundp ()
+  "Normal: `blacken-buffer' is fboundp after the package is loaded."
+  (should (fboundp 'blacken-buffer)))
+
+(ert-deftest test-prog-python-format-binding-resolves ()
+  "Normal: C-; f in `python-ts-mode-map' is bound to `blacken-buffer'."
+  (should (eq 'blacken-buffer
+              (lookup-key python-ts-mode-map (kbd "C-; f")))))
+
+(ert-deftest test-prog-python-format-executable-on-path ()
+  "Boundary: the `black' executable is on PATH (skipped if not installed)."
+  (format-test--skip-unless-executable "black")
+  (should (executable-find "black")))
+
+(provide 'test-prog-python--format-wiring)
+;;; test-prog-python--format-wiring.el ends here