test: add gloss-display test suite (red phase)

Four test files covering the gloss-display public API and pure helpers.
All 23 tests fail at this commit because the implementation is still a
stub. Format-candidate gets full N/B/E coverage. Render-entry gets the
pure-helper treatment. Pick-definition mocks completing-read at the
boundary. Show-entry has a single smoke test.

1 files changed, 84 insertions, 0 deletions

diff --git a/tests/test-gloss-display--format-candidate.el b/tests/test-gloss-display--format-candidate.el
new file mode 100644
index 0000000..29e077d
--- /dev/null
+++ b/tests/test-gloss-display--format-candidate.el
@@ -0,0 +1,84 @@
+;;; test-gloss-display--format-candidate.el --- Tests for gloss-display--format-candidate -*- lexical-binding: t -*-
+
+;; SPDX-License-Identifier: GPL-3.0-or-later
+
+;;; Commentary:
+;; Tests for the pure helper `gloss-display--format-candidate' covering
+;; Normal/Boundary/Error cases.  The helper takes a definition plist
+;; (:source SYM :text STRING) and returns a single-line "[source] text"
+;; row suitable for display in `completing-read'.
+
+;;; Code:
+
+(require 'ert)
+(require 'gloss-display)
+
+(ert-deftest test-gloss-display-format-candidate-normal-short-text ()
+  "Normal: short text formats as \"[source] text\" with no truncation."
+  (let ((result (gloss-display--format-candidate
+                 '(:source wiktionary :text "Hello world."))))
+    (should (equal result "[wiktionary] Hello world."))))
+
+(ert-deftest test-gloss-display-format-candidate-normal-different-source ()
+  "Normal: source symbol is rendered as its name inside brackets."
+  (let ((result (gloss-display--format-candidate
+                 '(:source dictionary-api :text "Some text."))))
+    (should (string-prefix-p "[dictionary-api] " result))))
+
+(ert-deftest test-gloss-display-format-candidate-boundary-empty-text ()
+  "Boundary: empty text yields the prefix only."
+  (let ((result (gloss-display--format-candidate
+                 '(:source wiktionary :text ""))))
+    (should (equal result "[wiktionary] "))))
+
+(ert-deftest test-gloss-display-format-candidate-boundary-single-char-text ()
+  "Boundary: one-character text is preserved verbatim."
+  (let ((result (gloss-display--format-candidate
+                 '(:source wiktionary :text "a"))))
+    (should (equal result "[wiktionary] a"))))
+
+(ert-deftest test-gloss-display-format-candidate-boundary-unicode-text ()
+  "Boundary: unicode characters in text are preserved."
+  (let ((result (gloss-display--format-candidate
+                 '(:source wiktionary :text "café — naïve résumé"))))
+    (should (equal result "[wiktionary] café — naïve résumé"))))
+
+(ert-deftest test-gloss-display-format-candidate-boundary-long-text-truncated ()
+  "Boundary: text longer than the cap is truncated with an ellipsis."
+  (let* ((long-text (make-string 200 ?x))
+         (result (gloss-display--format-candidate
+                  (list :source 'wiktionary :text long-text))))
+    (should (<= (length result) gloss-display--candidate-max-length))
+    (should (string-suffix-p "..." result))
+    (should (string-prefix-p "[wiktionary] " result))))
+
+(ert-deftest test-gloss-display-format-candidate-boundary-text-at-cap-not-truncated ()
+  "Boundary: text that fits exactly at the cap is not truncated."
+  (let* ((prefix-len (length "[wiktionary] "))
+         (text (make-string (- gloss-display--candidate-max-length prefix-len) ?y))
+         (result (gloss-display--format-candidate
+                  (list :source 'wiktionary :text text))))
+    (should (= (length result) gloss-display--candidate-max-length))
+    (should-not (string-suffix-p "..." result))))
+
+(ert-deftest test-gloss-display-format-candidate-boundary-missing-source ()
+  "Boundary: missing :source falls back to the literal \"unknown\" tag."
+  (let ((result (gloss-display--format-candidate
+                 '(:text "Some text."))))
+    (should (string-prefix-p "[unknown] " result))
+    (should (string-suffix-p "Some text." result))))
+
+(ert-deftest test-gloss-display-format-candidate-boundary-newlines-collapsed ()
+  "Boundary: embedded newlines are collapsed to spaces (single-line row)."
+  (let ((result (gloss-display--format-candidate
+                 '(:source wiktionary :text "First line.\nSecond line."))))
+    (should-not (string-match-p "\n" result))
+    (should (string-match-p "First line. Second line." result))))
+
+(ert-deftest test-gloss-display-format-candidate-error-non-list-input ()
+  "Error: passing a non-list raises `wrong-type-argument'."
+  (should-error (gloss-display--format-candidate "not a plist")
+                :type 'wrong-type-argument))
+
+(provide 'test-gloss-display--format-candidate)
+;;; test-gloss-display--format-candidate.el ends here