tests(textframe): Add display() tests

why: Verify interactive curses viewer behavior
what:
- Test RuntimeError when stdout is not a TTY
- Test curses.wrapper integration
- Test exit on q, Esc, Ctrl-C keys
- Test scroll navigation with arrow keys
- Test status line display

Author: tony

tests/textframe/test_display.py

@@ -0,0 +1,139 @@
+"""Tests for TextFrame.display() interactive viewer."""
+
+from __future__ import annotations
+
+import io
+import typing as t
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+from libtmux.textframe import TextFrame
+
+
+class TestDisplayTTYRequirement:
+    """Tests for display() TTY detection."""
+
+    def test_raises_when_not_tty(self) -> None:
+        """Verify display() raises RuntimeError when stdout is not a TTY.
+
+        This test simulates a non-interactive environment (e.g., piped output,
+        CI environment) where curses cannot function.
+        """
+        frame = TextFrame(content_width=10, content_height=2)
+        frame.set_content(["hello", "world"])
+
+        with (
+            patch("sys.stdout", new=io.StringIO()),
+            pytest.raises(RuntimeError, match="interactive terminal"),
+        ):
+            frame.display()
+
+    def test_calls_curses_wrapper_when_tty(self) -> None:
+        """Verify display() calls curses.wrapper when stdout is a TTY."""
+        frame = TextFrame(content_width=10, content_height=2)
+        frame.set_content(["hello", "world"])
+
+        with (
+            patch("sys.stdout.isatty", return_value=True),
+            patch("curses.wrapper") as mock_wrapper,
+        ):
+            frame.display()
+            mock_wrapper.assert_called_once()
+            # Verify it was called with _curses_display method
+            args = mock_wrapper.call_args[0]
+            assert args[0].__name__ == "_curses_display"
+
+
+class TestCursesDisplay:
+    """Tests for _curses_display() curses viewer implementation.
+
+    These tests mock curses module-level functions (curs_set, A_REVERSE)
+    since curses requires terminal initialization.
+    """
+
+    @pytest.fixture
+    def mock_curses(self) -> t.Generator[None, None, None]:
+        """Mock curses module-level functions that require initscr()."""
+        with (
+            patch("curses.curs_set"),
+            patch("curses.A_REVERSE", 0),
+        ):
+            yield
+
+    def test_quit_on_q_key(self, mock_curses: None) -> None:
+        """Verify viewer exits when q key is pressed."""
+        frame = TextFrame(content_width=10, content_height=2)
+        frame.set_content(["hello", "world"])
+
+        mock_stdscr = MagicMock()
+        mock_stdscr.getmaxyx.return_value = (24, 80)
+        mock_stdscr.getch.return_value = ord("q")
+
+        # Should exit cleanly without error
+        frame._curses_display(mock_stdscr)
+
+        # Verify basic curses setup was called
+        mock_stdscr.clear.assert_called()
+        mock_stdscr.refresh.assert_called()
+
+    def test_quit_on_escape_key(self, mock_curses: None) -> None:
+        """Verify viewer exits when Escape key is pressed."""
+        frame = TextFrame(content_width=10, content_height=2)
+        frame.set_content(["hello", "world"])
+
+        mock_stdscr = MagicMock()
+        mock_stdscr.getmaxyx.return_value = (24, 80)
+        mock_stdscr.getch.return_value = 27  # Escape key
+
+        frame._curses_display(mock_stdscr)
+        mock_stdscr.clear.assert_called()
+
+    def test_quit_on_keyboard_interrupt(self, mock_curses: None) -> None:
+        """Verify viewer exits cleanly on Ctrl-C."""
+        frame = TextFrame(content_width=10, content_height=2)
+        frame.set_content(["hello", "world"])
+
+        mock_stdscr = MagicMock()
+        mock_stdscr.getmaxyx.return_value = (24, 80)
+        mock_stdscr.getch.side_effect = KeyboardInterrupt()
+
+        # Should not raise, should exit cleanly
+        frame._curses_display(mock_stdscr)
+
+    def test_scroll_navigation_keys(self, mock_curses: None) -> None:
+        """Verify scroll navigation works with arrow keys."""
+        import curses as curses_module
+
+        frame = TextFrame(content_width=10, content_height=10)
+        frame.set_content([f"line {i}" for i in range(10)])
+
+        mock_stdscr = MagicMock()
+        mock_stdscr.getmaxyx.return_value = (5, 20)  # Small viewport
+
+        # Simulate: down arrow, then quit
+        mock_stdscr.getch.side_effect = [curses_module.KEY_DOWN, ord("q")]
+
+        frame._curses_display(mock_stdscr)
+
+        # Verify multiple refresh cycles occurred (initial + after navigation)
+        assert mock_stdscr.refresh.call_count >= 2
+
+    def test_status_line_displayed(self, mock_curses: None) -> None:
+        """Verify status line shows position and dimensions."""
+        frame = TextFrame(content_width=10, content_height=2)
+        frame.set_content(["hello", "world"])
+
+        mock_stdscr = MagicMock()
+        mock_stdscr.getmaxyx.return_value = (24, 80)
+        mock_stdscr.getch.return_value = ord("q")
+
+        frame._curses_display(mock_stdscr)
+
+        # Find the addstr call that contains status info
+        status_calls = [
+            call
+            for call in mock_stdscr.addstr.call_args_list
+            if len(call[0]) >= 3 and "q:quit" in str(call[0][2])
+        ]
+        assert len(status_calls) > 0, "Status line should be displayed"