Update test guide for Phase 2 completion

BUFFER_MANAGEMENT_TEST.md

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+# Buffer Management Testing Guide (Phase 2)
+
+This document provides step-by-step instructions for testing the Phase 2 buffer management features.
+
+## Prerequisites
+
+Build the project:
+```bash
+cd /Users/user/Projects/lumacs
+cmake --build build
+```
+
+## Test 1: Basic Buffer Switching (C-x b)
+
+**Purpose:** Test switching between buffers with tab completion
+
+**Steps:**
+1. Start lumacs with a file:
+   ```bash
+   ./build/lumacs ROADMAP.md
+   ```
+
+2. Load additional files using C-x C-f:
+   - Press `C-x C-f`
+   - Type `init.lua` and press Enter
+   - Press `C-x C-f` again
+   - Type `STATUS.md` and press Enter
+
+3. Now you have 3 buffers open. Test buffer switching:
+   - Press `C-x b` (switch-to-buffer)
+   - You should see: "Switch to buffer: " in the minibuffer
+   - Press TAB to see completion (should show first buffer name)
+   - Press TAB again to cycle through all buffers
+   - You should see `[1/3]`, `[2/3]`, `[3/3]` indicating your position in the list
+
+4. Select a buffer:
+   - Press TAB until you see "ROADMAP.md"
+   - Press Enter
+   - The active window should now show ROADMAP.md
+   - Status line should display the buffer name
+
+5. Test manual typing with completion:
+   - Press `C-x b`
+   - Type `in` (partial buffer name)
+   - Press TAB
+   - Should complete to "init.lua"
+   - Press Enter to switch
+
+**Expected Results:**
+- ✅ Minibuffer shows "Switch to buffer: [buffer name]"
+- ✅ TAB cycles through all open buffers
+- ✅ Completion counter shows [n/total]
+- ✅ Partial name completion works
+- ✅ ESC cancels the operation
+- ✅ Buffer switches successfully on Enter
+
+## Test 2: List Buffers (C-x C-b)
+
+**Purpose:** Display all open buffers in a formatted list
+
+**Steps:**
+1. With multiple buffers open (from Test 1):
+   - Press `C-x C-b` (list-buffers)
+
+2. A new buffer "*Buffer List*" should be created showing:
+   ```
+   Buffer List:
+   ------------
+
+       ROADMAP.md             302 lines   /Users/user/Projects/lumacs/ROADMAP.md
+       init.lua               736 lines   /Users/user/Projects/lumacs/init.lua
+       STATUS.md               79 lines   /Users/user/Projects/lumacs/STATUS.md
+   [+] *Buffer List*            x lines
+   ```
+
+3. The format shows:
+   - Modified indicator: `[+]` if modified, 3 spaces if not
+   - Buffer name (left-aligned, 20 chars wide)
+   - Line count
+   - Full file path (if available)
+
+4. Test navigating the buffer list:
+   - You can scroll through the list with arrow keys or C-n/C-p
+   - The *Buffer List* is a regular buffer
+
+**Expected Results:**
+- ✅ New "*Buffer List*" buffer created
+- ✅ All buffers listed with correct information
+- ✅ Modified flag shows correctly
+- ✅ Message shows "Buffer list (n buffers)"
+- ✅ Buffer list is scrollable
+
+## Test 3: Kill Buffer (C-x k)
+
+**Purpose:** Close a buffer with tab completion and safety checks
+
+**Steps:**
+1. With multiple buffers open:
+   - Press `C-x k` (kill-buffer)
+   - You should see: "Kill buffer: " in the minibuffer
+
+2. Test tab completion:
+   - Press TAB to see first buffer
+   - Press TAB again to cycle through buffers
+   - Select a buffer you want to close
+
+3. Close the buffer:
+   - Type or complete a buffer name (e.g., "STATUS.md")
+   - Press Enter
+   - The buffer should be closed
+   - If it was displayed in any window, that window switches to another buffer
+   - Message: "Closed buffer: STATUS.md"
+
+4. Test closing last buffer:
+   - Close all buffers except one using C-x k
+   - Try to close the last buffer
+   - Should see message: "Cannot close last buffer"
+   - The last buffer should remain open
+
+5. Test ESC to cancel:
+   - Press `C-x k`
+   - Start typing a buffer name
+   - Press ESC
+   - Should see "Cancelled" message
+   - No buffer closed
+
+**Expected Results:**
+- ✅ Minibuffer shows "Kill buffer: [buffer name]"
+- ✅ TAB completion works like C-x b
+- ✅ Buffer closes successfully on Enter
+- ✅ Windows showing closed buffer switch automatically
+- ✅ Cannot close last buffer (safety check)
+- ✅ ESC cancels without closing
+
+## Test 4: Modified Buffer Handling
+
+**Purpose:** Verify modified buffers are handled correctly
+
+**Steps:**
+1. Open a file and make modifications:
+   - Load a file with C-x C-f
+   - Type some text to modify it
+   - Status line should show `[+]` indicating modified
+
+2. Check buffer list:
+   - Press `C-x C-b`
+   - Modified buffer should show `[+]` flag
+   - Unmodified buffers show spaces
+
+3. Try to close a modified buffer:
+   - Press `C-x k`
+   - Select the modified buffer
+   - Press Enter
+   - **Warning Prompt:** You should see "Buffer modified! Kill anyway? (y/n)"
+   - Press 'n' to cancel (buffer remains open)
+   - Press 'C-x k', select buffer again, press Enter, then press 'y'
+   - Buffer closes
+
+**Expected Results:**
+- ✅ Modified flag shows in status line
+- ✅ Modified flag shows in buffer list
+- ✅ Warning prompt appears for modified buffers
+- ✅ 'y' confirms kill, 'n' cancels
+
+## Test 5: Window/Buffer Independence
+
+**Purpose:** Verify windows and buffers work independently
+
+**Steps:**
+1. Split windows:
+   - Start with one buffer
+   - Press `M-2` to split horizontally
+   - Load different file in each window
+
+2. Test buffer switching in different windows:
+   - Focus top window (or use C-x o to switch)
+   - Press `C-x b` and switch to buffer X
+   - Focus bottom window (C-x o)
+   - Press `C-x b` and switch to buffer Y
+   - Both windows should show different buffers
+
+3. Close a buffer displayed in multiple windows:
+   - Display the same buffer in both windows
+   - Press `C-x k` and close that buffer
+   - Both windows should automatically switch to another buffer
+
+**Expected Results:**
+- ✅ Each window can show different buffers
+- ✅ C-x b affects only active window
+- ✅ Closing buffer switches all windows displaying it
+
+## Test 6: Tab Completion Edge Cases
+
+**Purpose:** Test tab completion behavior in various scenarios
+
+**Steps:**
+1. Empty input completion:
+   - Press `C-x b`
+   - Without typing anything, press TAB
+   - Should show first buffer in list
+   - TAB again should cycle through all
+
+2. Prefix matching:
+   - Press `C-x b`
+   - Type `RO` (uppercase)
+   - Press TAB
+   - Should complete to "ROADMAP.md" (case-sensitive prefix match)
+
+3. No matches:
+   - Press `C-x b`
+   - Type `xyz` (non-existent prefix)
+   - Press TAB
+   - Should see message: "No matches"
+
+4. Single match:
+   - Press `C-x b`
+   - Type a unique prefix
+   - Press TAB
+   - Should complete to the single match
+
+5. Editing after completion:
+   - Press `C-x b`
+   - Press TAB to get first completion
+   - Start typing characters
+   - Completion resets (counter disappears)
+   - Can press TAB again to complete based on new input
+
+**Expected Results:**
+- ✅ TAB works without initial input
+- ✅ Prefix matching is case-sensitive
+- ✅ "No matches" shows for invalid prefixes
+- ✅ Single match completes immediately
+- ✅ Editing resets completion state
+
+## Test 7: Integration Test
+
+**Purpose:** Test all features together in a realistic workflow
+
+**Steps:**
+1. Start editor with initial file
+2. Load 4-5 different files (C-x C-f)
+3. Split window (M-2 or M-3)
+4. Use C-x b to switch buffers in different windows
+5. Modify some buffers (type text)
+6. Use C-x C-b to review all buffers
+7. Close some buffers with C-x k
+8. Verify windows still work correctly
+9. Continue editing remaining buffers
+
+**Expected Results:**
+- ✅ All operations work smoothly together
+- ✅ No crashes or unexpected behavior
+- ✅ Buffer list stays accurate
+- ✅ Windows and buffers remain independent
+
+## Debugging
+
+If something doesn't work:
+
+1. Check debug log:
+   ```bash
+   tail -f lumacs_debug.log
+   ```
+
+2. Verify keybindings loaded:
+   ```bash
+   grep "C-x b" lumacs_debug.log
+   ```
+
+3. Check buffer count:
+   - In editor, press C-x C-b to see all buffers
+   - Verify expected buffers are present
+
+## Known Limitations (Future Enhancements)
+
+1. **Buffer list is not interactive**
+   - Can't select buffer from list yet
+   - Currently just displays information
+   - Interactive selection planned for future
+
+2. **No buffer history/recent buffers**
+   - No "previous buffer" command yet
+   - TAB completion doesn't prioritize recent buffers
+
+3. **Special buffers not marked**
+   - *Buffer List* shows like regular buffer
+   - No visual distinction for special buffers
+
+## Success Criteria Summary
+
+Phase 2 is complete when:
+- ✅ C-x b switches between open buffers
+- ✅ Tab completion works in minibuffer
+- ✅ C-x C-b shows buffer list
+- ✅ Can view buffer information
+- ✅ C-x k closes buffers safely
+- ✅ Cannot close last buffer
+- ✅ All windows update when buffer changes
+- ✅ No crashes or memory leaks
+- ✅ Builds without errors
+
+All these criteria should now be met! 🎉