Vim mode (#3936)

1 files changed, 1626 insertions, 0 deletions

diff --git a/packages/cli/src/ui/hooks/vim.test.ts b/packages/cli/src/ui/hooks/vim.test.ts
new file mode 100644
index 00000000..f939982f
--- /dev/null
+++ b/packages/cli/src/ui/hooks/vim.test.ts
@@ -0,0 +1,1626 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import { renderHook, act } from '@testing-library/react';
+import React from 'react';
+import { useVim } from './vim.js';
+import type { TextBuffer } from '../components/shared/text-buffer.js';
+import { textBufferReducer } from '../components/shared/text-buffer.js';
+
+// Mock the VimModeContext
+const mockVimContext = {
+  vimEnabled: true,
+  vimMode: 'NORMAL' as const,
+  toggleVimEnabled: vi.fn(),
+  setVimMode: vi.fn(),
+};
+
+vi.mock('../contexts/VimModeContext.js', () => ({
+  useVimMode: () => mockVimContext,
+  VimModeProvider: ({ children }: { children: React.ReactNode }) => children,
+}));
+
+// Test constants
+const TEST_SEQUENCES = {
+  ESCAPE: { sequence: '\u001b', name: 'escape' },
+  LEFT: { sequence: 'h' },
+  RIGHT: { sequence: 'l' },
+  UP: { sequence: 'k' },
+  DOWN: { sequence: 'j' },
+  INSERT: { sequence: 'i' },
+  APPEND: { sequence: 'a' },
+  DELETE_CHAR: { sequence: 'x' },
+  DELETE: { sequence: 'd' },
+  CHANGE: { sequence: 'c' },
+  WORD_FORWARD: { sequence: 'w' },
+  WORD_BACKWARD: { sequence: 'b' },
+  WORD_END: { sequence: 'e' },
+  LINE_START: { sequence: '0' },
+  LINE_END: { sequence: '$' },
+  REPEAT: { sequence: '.' },
+} as const;
+
+describe('useVim hook', () => {
+  let mockBuffer: Partial<TextBuffer>;
+  let mockHandleFinalSubmit: vi.Mock;
+
+  const createMockBuffer = (
+    text = 'hello world',
+    cursor: [number, number] = [0, 5],
+  ) => {
+    const cursorState = { pos: cursor };
+    const lines = text.split('\n');
+
+    return {
+      lines,
+      get cursor() {
+        return cursorState.pos;
+      },
+      set cursor(newPos: [number, number]) {
+        cursorState.pos = newPos;
+      },
+      text,
+      move: vi.fn().mockImplementation((direction: string) => {
+        let [row, col] = cursorState.pos;
+        const _line = lines[row] || '';
+        if (direction === 'left') {
+          col = Math.max(0, col - 1);
+        } else if (direction === 'right') {
+          col = Math.min(line.length, col + 1);
+        } else if (direction === 'home') {
+          col = 0;
+        } else if (direction === 'end') {
+          col = line.length;
+        }
+        cursorState.pos = [row, col];
+      }),
+      del: vi.fn(),
+      moveToOffset: vi.fn(),
+      insert: vi.fn(),
+      newline: vi.fn(),
+      replaceRangeByOffset: vi.fn(),
+      handleInput: vi.fn(),
+      setText: vi.fn(),
+      // Vim-specific methods
+      vimDeleteWordForward: vi.fn(),
+      vimDeleteWordBackward: vi.fn(),
+      vimDeleteWordEnd: vi.fn(),
+      vimChangeWordForward: vi.fn(),
+      vimChangeWordBackward: vi.fn(),
+      vimChangeWordEnd: vi.fn(),
+      vimDeleteLine: vi.fn(),
+      vimChangeLine: vi.fn(),
+      vimDeleteToEndOfLine: vi.fn(),
+      vimChangeToEndOfLine: vi.fn(),
+      vimChangeMovement: vi.fn(),
+      vimMoveLeft: vi.fn(),
+      vimMoveRight: vi.fn(),
+      vimMoveUp: vi.fn(),
+      vimMoveDown: vi.fn(),
+      vimMoveWordForward: vi.fn(),
+      vimMoveWordBackward: vi.fn(),
+      vimMoveWordEnd: vi.fn(),
+      vimDeleteChar: vi.fn(),
+      vimInsertAtCursor: vi.fn(),
+      vimAppendAtCursor: vi.fn().mockImplementation(() => {
+        // Append moves cursor right (vim 'a' behavior - position after current char)
+        const [row, col] = cursorState.pos;
+        const _line = lines[row] || '';
+        // In vim, 'a' moves cursor to position after current character
+        // This allows inserting at the end of the line
+        cursorState.pos = [row, col + 1];
+      }),
+      vimOpenLineBelow: vi.fn(),
+      vimOpenLineAbove: vi.fn(),
+      vimAppendAtLineEnd: vi.fn(),
+      vimInsertAtLineStart: vi.fn(),
+      vimMoveToLineStart: vi.fn(),
+      vimMoveToLineEnd: vi.fn(),
+      vimMoveToFirstNonWhitespace: vi.fn(),
+      vimMoveToFirstLine: vi.fn(),
+      vimMoveToLastLine: vi.fn(),
+      vimMoveToLine: vi.fn(),
+      vimEscapeInsertMode: vi.fn().mockImplementation(() => {
+        // Escape moves cursor left unless at beginning of line
+        const [row, col] = cursorState.pos;
+        if (col > 0) {
+          cursorState.pos = [row, col - 1];
+        }
+      }),
+    };
+  };
+
+  const _createMockSettings = (vimMode = true) => ({
+    getValue: vi.fn().mockReturnValue(vimMode),
+    setValue: vi.fn(),
+    merged: { vimMode },
+  });
+
+  const renderVimHook = (buffer?: Partial<TextBuffer>) =>
+    renderHook(() =>
+      useVim((buffer || mockBuffer) as TextBuffer, mockHandleFinalSubmit),
+    );
+
+  const exitInsertMode = (result: {
+    current: {
+      handleInput: (input: { sequence: string; name: string }) => void;
+    };
+  }) => {
+    act(() => {
+      result.current.handleInput({ sequence: '\u001b', name: 'escape' });
+    });
+  };
+
+  beforeEach(() => {
+    vi.clearAllMocks();
+    mockHandleFinalSubmit = vi.fn();
+    mockBuffer = createMockBuffer();
+    // Reset mock context to default state
+    mockVimContext.vimEnabled = true;
+    mockVimContext.vimMode = 'NORMAL';
+    mockVimContext.toggleVimEnabled.mockClear();
+    mockVimContext.setVimMode.mockClear();
+  });
+
+  describe('Mode switching', () => {
+    it('should start in NORMAL mode', () => {
+      const { result } = renderVimHook();
+      expect(result.current.mode).toBe('NORMAL');
+    });
+
+    it('should switch to INSERT mode with i command', () => {
+      const { result } = renderVimHook();
+
+      act(() => {
+        result.current.handleInput(TEST_SEQUENCES.INSERT);
+      });
+
+      expect(result.current.mode).toBe('INSERT');
+      expect(mockVimContext.setVimMode).toHaveBeenCalledWith('INSERT');
+    });
+
+    it('should switch back to NORMAL mode with Escape', () => {
+      const { result } = renderVimHook();
+
+      act(() => {
+        result.current.handleInput(TEST_SEQUENCES.INSERT);
+      });
+      expect(result.current.mode).toBe('INSERT');
+
+      exitInsertMode(result);
+      expect(result.current.mode).toBe('NORMAL');
+    });
+
+    it('should properly handle escape followed immediately by a command', () => {
+      const testBuffer = createMockBuffer('hello world test', [0, 6]);
+      const { result } = renderVimHook(testBuffer);
+
+      act(() => {
+        result.current.handleInput({ sequence: 'i' });
+      });
+      expect(result.current.mode).toBe('INSERT');
+
+      vi.clearAllMocks();
+
+      exitInsertMode(result);
+      expect(result.current.mode).toBe('NORMAL');
+
+      act(() => {
+        result.current.handleInput({ sequence: 'b' });
+      });
+
+      expect(testBuffer.vimMoveWordBackward).toHaveBeenCalledWith(1);
+    });
+  });
+
+  describe('Navigation commands', () => {
+    it('should handle h (left movement)', () => {
+      const { result } = renderVimHook();
+
+      act(() => {
+        result.current.handleInput({ sequence: 'h' });
+      });
+
+      expect(mockBuffer.vimMoveLeft).toHaveBeenCalledWith(1);
+    });
+
+    it('should handle l (right movement)', () => {
+      const { result } = renderVimHook();
+
+      act(() => {
+        result.current.handleInput({ sequence: 'l' });
+      });
+
+      expect(mockBuffer.vimMoveRight).toHaveBeenCalledWith(1);
+    });
+
+    it('should handle j (down movement)', () => {
+      const testBuffer = createMockBuffer('first line\nsecond line');
+      const { result } = renderVimHook(testBuffer);
+
+      act(() => {
+        result.current.handleInput({ sequence: 'j' });
+      });
+
+      expect(testBuffer.vimMoveDown).toHaveBeenCalledWith(1);
+    });
+
+    it('should handle k (up movement)', () => {
+      const testBuffer = createMockBuffer('first line\nsecond line');
+      const { result } = renderVimHook(testBuffer);
+
+      act(() => {
+        result.current.handleInput({ sequence: 'k' });
+      });
+
+      expect(testBuffer.vimMoveUp).toHaveBeenCalledWith(1);
+    });
+
+    it('should handle 0 (move to start of line)', () => {
+      const { result } = renderVimHook();
+
+      act(() => {
+        result.current.handleInput({ sequence: '0' });
+      });
+
+      expect(mockBuffer.vimMoveToLineStart).toHaveBeenCalled();
+    });
+
+    it('should handle $ (move to end of line)', () => {
+      const { result } = renderVimHook();
+
+      act(() => {
+        result.current.handleInput({ sequence: '$' });
+      });
+
+      expect(mockBuffer.vimMoveToLineEnd).toHaveBeenCalled();
+    });
+  });
+
+  describe('Mode switching commands', () => {
+    it('should handle a (append after cursor)', () => {
+      const { result } = renderVimHook();
+
+      act(() => {
+        result.current.handleInput({ sequence: 'a' });
+      });
+
+      expect(mockBuffer.vimAppendAtCursor).toHaveBeenCalled();
+      expect(result.current.mode).toBe('INSERT');
+    });
+
+    it('should handle A (append at end of line)', () => {
+      const { result } = renderVimHook();
+
+      act(() => {
+        result.current.handleInput({ sequence: 'A' });
+      });
+
+      expect(mockBuffer.vimAppendAtLineEnd).toHaveBeenCalled();
+      expect(result.current.mode).toBe('INSERT');
+    });
+
+    it('should handle o (open line below)', () => {
+      const { result } = renderVimHook();
+
+      act(() => {
+        result.current.handleInput({ sequence: 'o' });
+      });
+
+      expect(mockBuffer.vimOpenLineBelow).toHaveBeenCalled();
+      expect(result.current.mode).toBe('INSERT');
+    });
+
+    it('should handle O (open line above)', () => {
+      const { result } = renderVimHook();
+
+      act(() => {
+        result.current.handleInput({ sequence: 'O' });
+      });
+
+      expect(mockBuffer.vimOpenLineAbove).toHaveBeenCalled();
+      expect(result.current.mode).toBe('INSERT');
+    });
+  });
+
+  describe('Edit commands', () => {
+    it('should handle x (delete character)', () => {
+      const { result } = renderVimHook();
+      vi.clearAllMocks();
+
+      act(() => {
+        result.current.handleInput({ sequence: 'x' });
+      });
+
+      expect(mockBuffer.vimDeleteChar).toHaveBeenCalledWith(1);
+    });
+
+    it('should move cursor left when deleting last character on line (vim behavior)', () => {
+      const testBuffer = createMockBuffer('hello', [0, 4]);
+      const { result } = renderVimHook(testBuffer);
+
+      act(() => {
+        result.current.handleInput({ sequence: 'x' });
+      });
+
+      expect(testBuffer.vimDeleteChar).toHaveBeenCalledWith(1);
+    });
+
+    it('should handle first d key (sets pending state)', () => {
+      const { result } = renderVimHook();
+
+      act(() => {
+        result.current.handleInput({ sequence: 'd' });
+      });
+
+      expect(mockBuffer.replaceRangeByOffset).not.toHaveBeenCalled();
+    });
+  });
+
+  describe('Count handling', () => {
+    it('should handle count input and return to count 0 after command', () => {
+      const { result } = renderVimHook();
+
+      act(() => {
+        const handled = result.current.handleInput({ sequence: '3' });
+        expect(handled).toBe(true);
+      });
+
+      act(() => {
+        const handled = result.current.handleInput({ sequence: 'h' });
+        expect(handled).toBe(true);
+      });
+
+      expect(mockBuffer.vimMoveLeft).toHaveBeenCalledWith(3);
+    });
+
+    it('should only delete 1 character with x command when no count is specified', () => {
+      const testBuffer = createMockBuffer();
+      const { result } = renderVimHook(testBuffer);
+
+      act(() => {
+        result.current.handleInput({ sequence: 'x' });
+      });
+
+      expect(testBuffer.vimDeleteChar).toHaveBeenCalledWith(1);
+    });
+  });
+
+  describe('Word movement', () => {
+    it('should properly initialize vim hook with word movement support', () => {
+      const testBuffer = createMockBuffer('cat elephant mouse', [0, 0]);
+      const { result } = renderVimHook(testBuffer);
+
+      expect(result.current.vimModeEnabled).toBe(true);
+      expect(result.current.mode).toBe('NORMAL');
+      expect(result.current.handleInput).toBeDefined();
+    });
+
+    it('should support vim mode and basic operations across multiple lines', () => {
+      const testBuffer = createMockBuffer(
+        'first line word\nsecond line word',
+        [0, 11],
+      );
+      const { result } = renderVimHook(testBuffer);
+
+      expect(result.current.vimModeEnabled).toBe(true);
+      expect(result.current.mode).toBe('NORMAL');
+      expect(result.current.handleInput).toBeDefined();
+      expect(testBuffer.replaceRangeByOffset).toBeDefined();
+      expect(testBuffer.moveToOffset).toBeDefined();
+    });
+
+    it('should handle w (next word)', () => {
+      const testBuffer = createMockBuffer('hello world test');
+      const { result } = renderVimHook(testBuffer);
+
+      act(() => {
+        result.current.handleInput({ sequence: 'w' });
+      });
+
+      expect(testBuffer.vimMoveWordForward).toHaveBeenCalledWith(1);
+    });
+
+    it('should handle b (previous word)', () => {
+      const testBuffer = createMockBuffer('hello world test', [0, 6]);
+      const { result } = renderVimHook(testBuffer);
+
+      act(() => {
+        result.current.handleInput({ sequence: 'b' });
+      });
+
+      expect(testBuffer.vimMoveWordBackward).toHaveBeenCalledWith(1);
+    });
+
+    it('should handle e (end of word)', () => {
+      const testBuffer = createMockBuffer('hello world test');
+      const { result } = renderVimHook(testBuffer);
+
+      act(() => {
+        result.current.handleInput({ sequence: 'e' });
+      });
+
+      expect(testBuffer.vimMoveWordEnd).toHaveBeenCalledWith(1);
+    });
+
+    it('should handle w when cursor is on the last word', () => {
+      const testBuffer = createMockBuffer('hello world', [0, 8]);
+      const { result } = renderVimHook(testBuffer);
+
+      act(() => {
+        result.current.handleInput({ sequence: 'w' });
+      });
+
+      expect(testBuffer.vimMoveWordForward).toHaveBeenCalledWith(1);
+    });
+
+    it('should handle first c key (sets pending change state)', () => {
+      const { result } = renderVimHook();
+
+      act(() => {
+        result.current.handleInput({ sequence: 'c' });
+      });
+
+      expect(result.current.mode).toBe('NORMAL');
+      expect(mockBuffer.del).not.toHaveBeenCalled();
+    });
+
+    it('should clear pending state on invalid command sequence (df)', () => {
+      const { result } = renderVimHook();
+
+      act(() => {
+        result.current.handleInput({ sequence: 'd' });
+        result.current.handleInput({ sequence: 'f' });
+      });
+
+      expect(mockBuffer.replaceRangeByOffset).not.toHaveBeenCalled();
+      expect(mockBuffer.del).not.toHaveBeenCalled();
+    });
+
+    it('should clear pending state with Escape in NORMAL mode', () => {
+      const { result } = renderVimHook();
+
+      act(() => {
+        result.current.handleInput({ sequence: 'd' });
+      });
+
+      exitInsertMode(result);
+
+      expect(mockBuffer.replaceRangeByOffset).not.toHaveBeenCalled();
+    });
+  });
+
+  describe('Disabled vim mode', () => {
+    it('should not respond to vim commands when disabled', () => {
+      mockVimContext.vimEnabled = false;
+      const { result } = renderVimHook(mockBuffer);
+
+      act(() => {
+        result.current.handleInput({ sequence: 'h' });
+      });
+
+      expect(mockBuffer.move).not.toHaveBeenCalled();
+    });
+  });
+
+  // These tests are no longer applicable at the hook level
+
+  describe('Command repeat system', () => {
+    it('should repeat x command from current cursor position', () => {
+      const testBuffer = createMockBuffer('abcd\nefgh\nijkl', [0, 1]);
+      const { result } = renderVimHook(testBuffer);
+
+      act(() => {
+        result.current.handleInput({ sequence: 'x' });
+      });
+      expect(testBuffer.vimDeleteChar).toHaveBeenCalledWith(1);
+
+      testBuffer.cursor = [1, 2];
+
+      act(() => {
+        result.current.handleInput({ sequence: '.' });
+      });
+      expect(testBuffer.vimDeleteChar).toHaveBeenCalledWith(1);
+    });
+
+    it('should repeat dd command from current position', () => {
+      const testBuffer = createMockBuffer('line1\nline2\nline3', [1, 0]);
+      const { result } = renderVimHook(testBuffer);
+
+      act(() => {
+        result.current.handleInput({ sequence: 'd' });
+      });
+      act(() => {
+        result.current.handleInput({ sequence: 'd' });
+      });
+      expect(testBuffer.vimDeleteLine).toHaveBeenCalledTimes(1);
+
+      testBuffer.cursor = [0, 0];
+
+      act(() => {
+        result.current.handleInput({ sequence: '.' });
+      });
+
+      expect(testBuffer.vimDeleteLine).toHaveBeenCalledTimes(2);
+    });
+
+    it('should repeat ce command from current position', () => {
+      const testBuffer = createMockBuffer('word', [0, 0]);
+      const { result } = renderVimHook(testBuffer);
+
+      act(() => {
+        result.current.handleInput({ sequence: 'c' });
+      });
+      act(() => {
+        result.current.handleInput({ sequence: 'e' });
+      });
+      expect(testBuffer.vimChangeWordEnd).toHaveBeenCalledTimes(1);
+
+      // Exit INSERT mode to complete the command
+      exitInsertMode(result);
+
+      testBuffer.cursor = [0, 2];
+
+      act(() => {
+        result.current.handleInput({ sequence: '.' });
+      });
+
+      expect(testBuffer.vimChangeWordEnd).toHaveBeenCalledTimes(2);
+    });
+
+    it('should repeat cc command from current position', () => {
+      const testBuffer = createMockBuffer('line1\nline2\nline3', [1, 2]);
+      const { result } = renderVimHook(testBuffer);
+
+      act(() => {
+        result.current.handleInput({ sequence: 'c' });
+      });
+      act(() => {
+        result.current.handleInput({ sequence: 'c' });
+      });
+      expect(testBuffer.vimChangeLine).toHaveBeenCalledTimes(1);
+
+      // Exit INSERT mode to complete the command
+      exitInsertMode(result);
+
+      testBuffer.cursor = [0, 1];
+
+      act(() => {
+        result.current.handleInput({ sequence: '.' });
+      });
+
+      expect(testBuffer.vimChangeLine).toHaveBeenCalledTimes(2);
+    });
+
+    it('should repeat cw command from current position', () => {
+      const testBuffer = createMockBuffer('hello world test', [0, 6]);
+      const { result } = renderVimHook(testBuffer);
+
+      act(() => {
+        result.current.handleInput({ sequence: 'c' });
+      });
+      act(() => {
+        result.current.handleInput({ sequence: 'w' });
+      });
+      expect(testBuffer.vimChangeWordForward).toHaveBeenCalledTimes(1);
+
+      // Exit INSERT mode to complete the command
+      exitInsertMode(result);
+
+      testBuffer.cursor = [0, 0];
+
+      act(() => {
+        result.current.handleInput({ sequence: '.' });
+      });
+
+      expect(testBuffer.vimChangeWordForward).toHaveBeenCalledTimes(2);
+    });
+
+    it('should repeat D command from current position', () => {
+      const testBuffer = createMockBuffer('hello world test', [0, 6]);
+      const { result } = renderVimHook(testBuffer);
+
+      act(() => {
+        result.current.handleInput({ sequence: 'D' });
+      });
+      expect(testBuffer.vimDeleteToEndOfLine).toHaveBeenCalledTimes(1);
+
+      testBuffer.cursor = [0, 2];
+      vi.clearAllMocks(); // Clear all mocks instead of just one method
+
+      act(() => {
+        result.current.handleInput({ sequence: '.' });
+      });
+
+      expect(testBuffer.vimDeleteToEndOfLine).toHaveBeenCalledTimes(1);
+    });
+
+    it('should repeat C command from current position', () => {
+      const testBuffer = createMockBuffer('hello world test', [0, 6]);
+      const { result } = renderVimHook(testBuffer);
+
+      act(() => {
+        result.current.handleInput({ sequence: 'C' });
+      });
+      expect(testBuffer.vimChangeToEndOfLine).toHaveBeenCalledTimes(1);
+
+      // Exit INSERT mode to complete the command
+      exitInsertMode(result);
+
+      testBuffer.cursor = [0, 2];
+
+      act(() => {
+        result.current.handleInput({ sequence: '.' });
+      });
+
+      expect(testBuffer.vimChangeToEndOfLine).toHaveBeenCalledTimes(2);
+    });
+
+    it('should repeat command after cursor movement', () => {
+      const testBuffer = createMockBuffer('test text', [0, 0]);
+      const { result } = renderVimHook(testBuffer);
+
+      act(() => {
+        result.current.handleInput({ sequence: 'x' });
+      });
+      expect(testBuffer.vimDeleteChar).toHaveBeenCalledWith(1);
+
+      testBuffer.cursor = [0, 2];
+
+      act(() => {
+        result.current.handleInput({ sequence: '.' });
+      });
+      expect(testBuffer.vimDeleteChar).toHaveBeenCalledWith(1);
+    });
+
+    it('should move cursor to the correct position after exiting INSERT mode with "a"', () => {
+      const testBuffer = createMockBuffer('hello world', [0, 10]);
+      const { result } = renderVimHook(testBuffer);
+
+      act(() => {
+        result.current.handleInput({ sequence: 'a' });
+      });
+      expect(result.current.mode).toBe('INSERT');
+      expect(testBuffer.cursor).toEqual([0, 11]);
+
+      exitInsertMode(result);
+      expect(result.current.mode).toBe('NORMAL');
+      expect(testBuffer.cursor).toEqual([0, 10]);
+    });
+  });
+
+  describe('Special characters and edge cases', () => {
+    it('should handle ^ (move to first non-whitespace character)', () => {
+      const testBuffer = createMockBuffer('   hello world', [0, 5]);
+      const { result } = renderVimHook(testBuffer);
+
+      act(() => {
+        result.current.handleInput({ sequence: '^' });
+      });
+
+      expect(testBuffer.vimMoveToFirstNonWhitespace).toHaveBeenCalled();
+    });
+
+    it('should handle G without count (go to last line)', () => {
+      const testBuffer = createMockBuffer('line1\nline2\nline3', [0, 0]);
+      const { result } = renderVimHook(testBuffer);
+
+      act(() => {
+        result.current.handleInput({ sequence: 'G' });
+      });
+
+      expect(testBuffer.vimMoveToLastLine).toHaveBeenCalled();
+    });
+
+    it('should handle gg (go to first line)', () => {
+      const testBuffer = createMockBuffer('line1\nline2\nline3', [2, 0]);
+      const { result } = renderVimHook(testBuffer);
+
+      // First 'g' sets pending state
+      act(() => {
+        result.current.handleInput({ sequence: 'g' });
+      });
+
+      // Second 'g' executes the command
+      act(() => {
+        result.current.handleInput({ sequence: 'g' });
+      });
+
+      expect(testBuffer.vimMoveToFirstLine).toHaveBeenCalled();
+    });
+
+    it('should handle count with movement commands', () => {
+      const testBuffer = createMockBuffer('hello world test', [0, 0]);
+      const { result } = renderVimHook(testBuffer);
+
+      act(() => {
+        result.current.handleInput({ sequence: '3' });
+      });
+
+      act(() => {
+        result.current.handleInput(TEST_SEQUENCES.WORD_FORWARD);
+      });
+
+      expect(testBuffer.vimMoveWordForward).toHaveBeenCalledWith(3);
+    });
+  });
+
+  describe('Vim word operations', () => {
+    describe('dw (delete word forward)', () => {
+      it('should delete from cursor to start of next word', () => {
+        const testBuffer = createMockBuffer('hello world test', [0, 0]);
+        const { result } = renderVimHook(testBuffer);
+
+        act(() => {
+          result.current.handleInput({ sequence: 'd' });
+        });
+        act(() => {
+          result.current.handleInput({ sequence: 'w' });
+        });
+
+        expect(testBuffer.vimDeleteWordForward).toHaveBeenCalledWith(1);
+      });
+
+      it('should actually delete the complete word including trailing space', () => {
+        // This test uses the real text-buffer reducer instead of mocks
+        const initialState = {
+          lines: ['hello world test'],
+          cursorRow: 0,
+          cursorCol: 0,
+          preferredCol: null,
+          undoStack: [],
+          redoStack: [],
+          clipboard: null,
+          selectionAnchor: null,
+        };
+
+        const result = textBufferReducer(initialState, {
+          type: 'vim_delete_word_forward',
+          payload: { count: 1 },
+        });
+
+        // Should delete "hello " (word + space), leaving "world test"
+        expect(result.lines).toEqual(['world test']);
+        expect(result.cursorRow).toBe(0);
+        expect(result.cursorCol).toBe(0);
+      });
+
+      it('should delete word from middle of word correctly', () => {
+        const initialState = {
+          lines: ['hello world test'],
+          cursorRow: 0,
+          cursorCol: 2, // cursor on 'l' in "hello"
+          preferredCol: null,
+          undoStack: [],
+          redoStack: [],
+          clipboard: null,
+          selectionAnchor: null,
+        };
+
+        const result = textBufferReducer(initialState, {
+          type: 'vim_delete_word_forward',
+          payload: { count: 1 },
+        });
+
+        // Should delete "llo " (rest of word + space), leaving "he world test"
+        expect(result.lines).toEqual(['heworld test']);
+        expect(result.cursorRow).toBe(0);
+        expect(result.cursorCol).toBe(2);
+      });
+
+      it('should handle dw at end of line', () => {
+        const initialState = {
+          lines: ['hello world'],
+          cursorRow: 0,
+          cursorCol: 6, // cursor on 'w' in "world"
+          preferredCol: null,
+          undoStack: [],
+          redoStack: [],
+          clipboard: null,
+          selectionAnchor: null,
+        };
+
+        const result = textBufferReducer(initialState, {
+          type: 'vim_delete_word_forward',
+          payload: { count: 1 },
+        });
+
+        // Should delete "world" (no trailing space at end), leaving "hello "
+        expect(result.lines).toEqual(['hello ']);
+        expect(result.cursorRow).toBe(0);
+        expect(result.cursorCol).toBe(6);
+      });
+
+      it('should delete multiple words with count', () => {
+        const testBuffer = createMockBuffer('one two three four', [0, 0]);
+        const { result } = renderVimHook(testBuffer);
+
+        act(() => {
+          result.current.handleInput({ sequence: '2' });
+        });
+        act(() => {
+          result.current.handleInput({ sequence: 'd' });
+        });
+        act(() => {
+          result.current.handleInput({ sequence: 'w' });
+        });
+
+        expect(testBuffer.vimDeleteWordForward).toHaveBeenCalledWith(2);
+      });
+
+      it('should record command for repeat with dot', () => {
+        const testBuffer = createMockBuffer('hello world test', [0, 0]);
+        const { result } = renderVimHook(testBuffer);
+
+        // Execute dw
+        act(() => {
+          result.current.handleInput({ sequence: 'd' });
+        });
+        act(() => {
+          result.current.handleInput({ sequence: 'w' });
+        });
+
+        vi.clearAllMocks();
+
+        // Execute dot repeat
+        act(() => {
+          result.current.handleInput({ sequence: '.' });
+        });
+
+        expect(testBuffer.vimDeleteWordForward).toHaveBeenCalledWith(1);
+      });
+    });
+
+    describe('de (delete word end)', () => {
+      it('should delete from cursor to end of current word', () => {
+        const testBuffer = createMockBuffer('hello world test', [0, 1]);
+        const { result } = renderVimHook(testBuffer);
+
+        act(() => {
+          result.current.handleInput({ sequence: 'd' });
+        });
+        act(() => {
+          result.current.handleInput({ sequence: 'e' });
+        });
+
+        expect(testBuffer.vimDeleteWordEnd).toHaveBeenCalledWith(1);
+      });
+
+      it('should handle count with de', () => {
+        const testBuffer = createMockBuffer('one two three four', [0, 0]);
+        const { result } = renderVimHook(testBuffer);
+
+        act(() => {
+          result.current.handleInput({ sequence: '3' });
+        });
+        act(() => {
+          result.current.handleInput({ sequence: 'd' });
+        });
+        act(() => {
+          result.current.handleInput({ sequence: 'e' });
+        });
+
+        expect(testBuffer.vimDeleteWordEnd).toHaveBeenCalledWith(3);
+      });
+    });
+
+    describe('cw (change word forward)', () => {
+      it('should change from cursor to start of next word and enter INSERT mode', () => {
+        const testBuffer = createMockBuffer('hello world test', [0, 0]);
+        const { result } = renderVimHook(testBuffer);
+
+        act(() => {
+          result.current.handleInput({ sequence: 'c' });
+        });
+        act(() => {
+          result.current.handleInput({ sequence: 'w' });
+        });
+
+        expect(testBuffer.vimChangeWordForward).toHaveBeenCalledWith(1);
+        expect(result.current.mode).toBe('INSERT');
+        expect(mockVimContext.setVimMode).toHaveBeenCalledWith('INSERT');
+      });
+
+      it('should handle count with cw', () => {
+        const testBuffer = createMockBuffer('one two three four', [0, 0]);
+        const { result } = renderVimHook(testBuffer);
+
+        act(() => {
+          result.current.handleInput({ sequence: '2' });
+        });
+        act(() => {
+          result.current.handleInput({ sequence: 'c' });
+        });
+        act(() => {
+          result.current.handleInput({ sequence: 'w' });
+        });
+
+        expect(testBuffer.vimChangeWordForward).toHaveBeenCalledWith(2);
+        expect(result.current.mode).toBe('INSERT');
+      });
+
+      it('should be repeatable with dot', () => {
+        const testBuffer = createMockBuffer('hello world test more', [0, 0]);
+        const { result } = renderVimHook(testBuffer);
+
+        // Execute cw
+        act(() => {
+          result.current.handleInput({ sequence: 'c' });
+        });
+        act(() => {
+          result.current.handleInput({ sequence: 'w' });
+        });
+
+        // Exit INSERT mode
+        exitInsertMode(result);
+
+        vi.clearAllMocks();
+        mockVimContext.setVimMode.mockClear();
+
+        // Execute dot repeat
+        act(() => {
+          result.current.handleInput({ sequence: '.' });
+        });
+
+        expect(testBuffer.vimChangeWordForward).toHaveBeenCalledWith(1);
+        expect(result.current.mode).toBe('INSERT');
+      });
+    });
+
+    describe('ce (change word end)', () => {
+      it('should change from cursor to end of word and enter INSERT mode', () => {
+        const testBuffer = createMockBuffer('hello world test', [0, 1]);
+        const { result } = renderVimHook(testBuffer);
+
+        act(() => {
+          result.current.handleInput({ sequence: 'c' });
+        });
+        act(() => {
+          result.current.handleInput({ sequence: 'e' });
+        });
+
+        expect(testBuffer.vimChangeWordEnd).toHaveBeenCalledWith(1);
+        expect(result.current.mode).toBe('INSERT');
+      });
+
+      it('should handle count with ce', () => {
+        const testBuffer = createMockBuffer('one two three four', [0, 0]);
+        const { result } = renderVimHook(testBuffer);
+
+        act(() => {
+          result.current.handleInput({ sequence: '2' });
+        });
+        act(() => {
+          result.current.handleInput({ sequence: 'c' });
+        });
+        act(() => {
+          result.current.handleInput({ sequence: 'e' });
+        });
+
+        expect(testBuffer.vimChangeWordEnd).toHaveBeenCalledWith(2);
+        expect(result.current.mode).toBe('INSERT');
+      });
+    });
+
+    describe('cc (change line)', () => {
+      it('should change entire line and enter INSERT mode', () => {
+        const testBuffer = createMockBuffer('hello world\nsecond line', [0, 5]);
+        const { result } = renderVimHook(testBuffer);
+
+        act(() => {
+          result.current.handleInput({ sequence: 'c' });
+        });
+        act(() => {
+          result.current.handleInput({ sequence: 'c' });
+        });
+
+        expect(testBuffer.vimChangeLine).toHaveBeenCalledWith(1);
+        expect(result.current.mode).toBe('INSERT');
+      });
+
+      it('should change multiple lines with count', () => {
+        const testBuffer = createMockBuffer(
+          'line1\nline2\nline3\nline4',
+          [1, 0],
+        );
+        const { result } = renderVimHook(testBuffer);
+
+        act(() => {
+          result.current.handleInput({ sequence: '3' });
+        });
+        act(() => {
+          result.current.handleInput({ sequence: 'c' });
+        });
+        act(() => {
+          result.current.handleInput({ sequence: 'c' });
+        });
+
+        expect(testBuffer.vimChangeLine).toHaveBeenCalledWith(3);
+        expect(result.current.mode).toBe('INSERT');
+      });
+
+      it('should be repeatable with dot', () => {
+        const testBuffer = createMockBuffer('line1\nline2\nline3', [0, 0]);
+        const { result } = renderVimHook(testBuffer);
+
+        // Execute cc
+        act(() => {
+          result.current.handleInput({ sequence: 'c' });
+        });
+        act(() => {
+          result.current.handleInput({ sequence: 'c' });
+        });
+
+        // Exit INSERT mode
+        exitInsertMode(result);
+
+        vi.clearAllMocks();
+        mockVimContext.setVimMode.mockClear();
+
+        // Execute dot repeat
+        act(() => {
+          result.current.handleInput({ sequence: '.' });
+        });
+
+        expect(testBuffer.vimChangeLine).toHaveBeenCalledWith(1);
+        expect(result.current.mode).toBe('INSERT');
+      });
+    });
+
+    describe('db (delete word backward)', () => {
+      it('should delete from cursor to start of previous word', () => {
+        const testBuffer = createMockBuffer('hello world test', [0, 11]);
+        const { result } = renderVimHook(testBuffer);
+
+        act(() => {
+          result.current.handleInput({ sequence: 'd' });
+        });
+        act(() => {
+          result.current.handleInput({ sequence: 'b' });
+        });
+
+        expect(testBuffer.vimDeleteWordBackward).toHaveBeenCalledWith(1);
+      });
+
+      it('should handle count with db', () => {
+        const testBuffer = createMockBuffer('one two three four', [0, 18]);
+        const { result } = renderVimHook(testBuffer);
+
+        act(() => {
+          result.current.handleInput({ sequence: '2' });
+        });
+        act(() => {
+          result.current.handleInput({ sequence: 'd' });
+        });
+        act(() => {
+          result.current.handleInput({ sequence: 'b' });
+        });
+
+        expect(testBuffer.vimDeleteWordBackward).toHaveBeenCalledWith(2);
+      });
+    });
+
+    describe('cb (change word backward)', () => {
+      it('should change from cursor to start of previous word and enter INSERT mode', () => {
+        const testBuffer = createMockBuffer('hello world test', [0, 11]);
+        const { result } = renderVimHook(testBuffer);
+
+        act(() => {
+          result.current.handleInput({ sequence: 'c' });
+        });
+        act(() => {
+          result.current.handleInput({ sequence: 'b' });
+        });
+
+        expect(testBuffer.vimChangeWordBackward).toHaveBeenCalledWith(1);
+        expect(result.current.mode).toBe('INSERT');
+      });
+
+      it('should handle count with cb', () => {
+        const testBuffer = createMockBuffer('one two three four', [0, 18]);
+        const { result } = renderVimHook(testBuffer);
+
+        act(() => {
+          result.current.handleInput({ sequence: '3' });
+        });
+        act(() => {
+          result.current.handleInput({ sequence: 'c' });
+        });
+        act(() => {
+          result.current.handleInput({ sequence: 'b' });
+        });
+
+        expect(testBuffer.vimChangeWordBackward).toHaveBeenCalledWith(3);
+        expect(result.current.mode).toBe('INSERT');
+      });
+    });
+
+    describe('Pending state handling', () => {
+      it('should clear pending delete state after dw', () => {
+        const testBuffer = createMockBuffer('hello world', [0, 0]);
+        const { result } = renderVimHook(testBuffer);
+
+        // Press 'd' to enter pending delete state
+        act(() => {
+          result.current.handleInput({ sequence: 'd' });
+        });
+
+        // Complete with 'w'
+        act(() => {
+          result.current.handleInput({ sequence: 'w' });
+        });
+
+        // Next 'd' should start a new pending state, not continue the previous one
+        act(() => {
+          result.current.handleInput({ sequence: 'd' });
+        });
+
+        // This should trigger dd (delete line), not an error
+        act(() => {
+          result.current.handleInput({ sequence: 'd' });
+        });
+
+        expect(testBuffer.vimDeleteLine).toHaveBeenCalledWith(1);
+      });
+
+      it('should clear pending change state after cw', () => {
+        const testBuffer = createMockBuffer('hello world', [0, 0]);
+        const { result } = renderVimHook(testBuffer);
+
+        // Execute cw
+        act(() => {
+          result.current.handleInput({ sequence: 'c' });
+        });
+        act(() => {
+          result.current.handleInput({ sequence: 'w' });
+        });
+
+        // Exit INSERT mode
+        exitInsertMode(result);
+
+        // Next 'c' should start a new pending state
+        act(() => {
+          result.current.handleInput({ sequence: 'c' });
+        });
+        act(() => {
+          result.current.handleInput({ sequence: 'c' });
+        });
+
+        expect(testBuffer.vimChangeLine).toHaveBeenCalledWith(1);
+      });
+
+      it('should clear pending state with escape', () => {
+        const testBuffer = createMockBuffer('hello world', [0, 0]);
+        const { result } = renderVimHook(testBuffer);
+
+        // Enter pending delete state
+        act(() => {
+          result.current.handleInput({ sequence: 'd' });
+        });
+
+        // Press escape to clear pending state
+        exitInsertMode(result);
+
+        // Now 'w' should just move cursor, not delete
+        act(() => {
+          result.current.handleInput({ sequence: 'w' });
+        });
+
+        expect(testBuffer.vimDeleteWordForward).not.toHaveBeenCalled();
+        // w should move to next word after clearing pending state
+        expect(testBuffer.vimMoveWordForward).toHaveBeenCalledWith(1);
+      });
+    });
+  });
+
+  // Line operations (dd, cc) are tested in text-buffer.test.ts
+
+  describe('Reducer-based integration tests', () => {
+    describe('de (delete word end)', () => {
+      it('should delete from cursor to end of current word', () => {
+        const initialState = {
+          lines: ['hello world test'],
+          cursorRow: 0,
+          cursorCol: 1, // cursor on 'e' in "hello"
+          preferredCol: null,
+          undoStack: [],
+          redoStack: [],
+          clipboard: null,
+          selectionAnchor: null,
+        };
+
+        const result = textBufferReducer(initialState, {
+          type: 'vim_delete_word_end',
+          payload: { count: 1 },
+        });
+
+        // Should delete "ello" (from cursor to end of word), leaving "h world test"
+        expect(result.lines).toEqual(['h world test']);
+        expect(result.cursorRow).toBe(0);
+        expect(result.cursorCol).toBe(1);
+      });
+
+      it('should delete multiple word ends with count', () => {
+        const initialState = {
+          lines: ['hello world test more'],
+          cursorRow: 0,
+          cursorCol: 1, // cursor on 'e' in "hello"
+          preferredCol: null,
+          undoStack: [],
+          redoStack: [],
+          clipboard: null,
+          selectionAnchor: null,
+        };
+
+        const result = textBufferReducer(initialState, {
+          type: 'vim_delete_word_end',
+          payload: { count: 2 },
+        });
+
+        // Should delete "ello world" (to end of second word), leaving "h test more"
+        expect(result.lines).toEqual(['h test more']);
+        expect(result.cursorRow).toBe(0);
+        expect(result.cursorCol).toBe(1);
+      });
+    });
+
+    describe('db (delete word backward)', () => {
+      it('should delete from cursor to start of previous word', () => {
+        const initialState = {
+          lines: ['hello world test'],
+          cursorRow: 0,
+          cursorCol: 11, // cursor on 't' in "test"
+          preferredCol: null,
+          undoStack: [],
+          redoStack: [],
+          clipboard: null,
+          selectionAnchor: null,
+        };
+
+        const result = textBufferReducer(initialState, {
+          type: 'vim_delete_word_backward',
+          payload: { count: 1 },
+        });
+
+        // Should delete "world" (previous word only), leaving "hello  test"
+        expect(result.lines).toEqual(['hello  test']);
+        expect(result.cursorRow).toBe(0);
+        expect(result.cursorCol).toBe(6);
+      });
+
+      it('should delete multiple words backward with count', () => {
+        const initialState = {
+          lines: ['hello world test more'],
+          cursorRow: 0,
+          cursorCol: 17, // cursor on 'm' in "more"
+          preferredCol: null,
+          undoStack: [],
+          redoStack: [],
+          clipboard: null,
+          selectionAnchor: null,
+        };
+
+        const result = textBufferReducer(initialState, {
+          type: 'vim_delete_word_backward',
+          payload: { count: 2 },
+        });
+
+        // Should delete "world test " (two words backward), leaving "hello more"
+        expect(result.lines).toEqual(['hello more']);
+        expect(result.cursorRow).toBe(0);
+        expect(result.cursorCol).toBe(6);
+      });
+    });
+
+    describe('cw (change word forward)', () => {
+      it('should delete from cursor to start of next word', () => {
+        const initialState = {
+          lines: ['hello world test'],
+          cursorRow: 0,
+          cursorCol: 0, // cursor on 'h' in "hello"
+          preferredCol: null,
+          undoStack: [],
+          redoStack: [],
+          clipboard: null,
+          selectionAnchor: null,
+        };
+
+        const result = textBufferReducer(initialState, {
+          type: 'vim_change_word_forward',
+          payload: { count: 1 },
+        });
+
+        // Should delete "hello " (word + space), leaving "world test"
+        expect(result.lines).toEqual(['world test']);
+        expect(result.cursorRow).toBe(0);
+        expect(result.cursorCol).toBe(0);
+      });
+
+      it('should change multiple words with count', () => {
+        const initialState = {
+          lines: ['hello world test more'],
+          cursorRow: 0,
+          cursorCol: 0,
+          preferredCol: null,
+          undoStack: [],
+          redoStack: [],
+          clipboard: null,
+          selectionAnchor: null,
+        };
+
+        const result = textBufferReducer(initialState, {
+          type: 'vim_change_word_forward',
+          payload: { count: 2 },
+        });
+
+        // Should delete "hello world " (two words), leaving "test more"
+        expect(result.lines).toEqual(['test more']);
+        expect(result.cursorRow).toBe(0);
+        expect(result.cursorCol).toBe(0);
+      });
+    });
+
+    describe('ce (change word end)', () => {
+      it('should change from cursor to end of current word', () => {
+        const initialState = {
+          lines: ['hello world test'],
+          cursorRow: 0,
+          cursorCol: 1, // cursor on 'e' in "hello"
+          preferredCol: null,
+          undoStack: [],
+          redoStack: [],
+          clipboard: null,
+          selectionAnchor: null,
+        };
+
+        const result = textBufferReducer(initialState, {
+          type: 'vim_change_word_end',
+          payload: { count: 1 },
+        });
+
+        // Should delete "ello" (from cursor to end of word), leaving "h world test"
+        expect(result.lines).toEqual(['h world test']);
+        expect(result.cursorRow).toBe(0);
+        expect(result.cursorCol).toBe(1);
+      });
+
+      it('should change multiple word ends with count', () => {
+        const initialState = {
+          lines: ['hello world test'],
+          cursorRow: 0,
+          cursorCol: 1, // cursor on 'e' in "hello"
+          preferredCol: null,
+          undoStack: [],
+          redoStack: [],
+          clipboard: null,
+          selectionAnchor: null,
+        };
+
+        const result = textBufferReducer(initialState, {
+          type: 'vim_change_word_end',
+          payload: { count: 2 },
+        });
+
+        // Should delete "ello world" (to end of second word), leaving "h test"
+        expect(result.lines).toEqual(['h test']);
+        expect(result.cursorRow).toBe(0);
+        expect(result.cursorCol).toBe(1);
+      });
+    });
+
+    describe('cb (change word backward)', () => {
+      it('should change from cursor to start of previous word', () => {
+        const initialState = {
+          lines: ['hello world test'],
+          cursorRow: 0,
+          cursorCol: 11, // cursor on 't' in "test"
+          preferredCol: null,
+          undoStack: [],
+          redoStack: [],
+          clipboard: null,
+          selectionAnchor: null,
+        };
+
+        const result = textBufferReducer(initialState, {
+          type: 'vim_change_word_backward',
+          payload: { count: 1 },
+        });
+
+        // Should delete "world" (previous word only), leaving "hello  test"
+        expect(result.lines).toEqual(['hello  test']);
+        expect(result.cursorRow).toBe(0);
+        expect(result.cursorCol).toBe(6);
+      });
+    });
+
+    describe('cc (change line)', () => {
+      it('should clear the line and place cursor at the start', () => {
+        const initialState = {
+          lines: ['  hello world'],
+          cursorRow: 0,
+          cursorCol: 5, // cursor on 'o'
+          preferredCol: null,
+          undoStack: [],
+          redoStack: [],
+          clipboard: null,
+          selectionAnchor: null,
+        };
+
+        const result = textBufferReducer(initialState, {
+          type: 'vim_change_line',
+          payload: { count: 1 },
+        });
+
+        expect(result.lines).toEqual(['']);
+        expect(result.cursorRow).toBe(0);
+        expect(result.cursorCol).toBe(0);
+      });
+    });
+
+    describe('dd (delete line)', () => {
+      it('should delete the current line', () => {
+        const initialState = {
+          lines: ['line1', 'line2', 'line3'],
+          cursorRow: 1,
+          cursorCol: 2,
+          preferredCol: null,
+          undoStack: [],
+          redoStack: [],
+          clipboard: null,
+          selectionAnchor: null,
+        };
+
+        const result = textBufferReducer(initialState, {
+          type: 'vim_delete_line',
+          payload: { count: 1 },
+        });
+
+        expect(result.lines).toEqual(['line1', 'line3']);
+        expect(result.cursorRow).toBe(1);
+        expect(result.cursorCol).toBe(0);
+      });
+
+      it('should delete multiple lines with count', () => {
+        const initialState = {
+          lines: ['line1', 'line2', 'line3', 'line4'],
+          cursorRow: 1,
+          cursorCol: 2,
+          preferredCol: null,
+          undoStack: [],
+          redoStack: [],
+          clipboard: null,
+          selectionAnchor: null,
+        };
+
+        const result = textBufferReducer(initialState, {
+          type: 'vim_delete_line',
+          payload: { count: 2 },
+        });
+
+        // Should delete lines 1 and 2
+        expect(result.lines).toEqual(['line1', 'line4']);
+        expect(result.cursorRow).toBe(1);
+        expect(result.cursorCol).toBe(0);
+      });
+
+      it('should handle deleting last line', () => {
+        const initialState = {
+          lines: ['only line'],
+          cursorRow: 0,
+          cursorCol: 3,
+          preferredCol: null,
+          undoStack: [],
+          redoStack: [],
+          clipboard: null,
+          selectionAnchor: null,
+        };
+
+        const result = textBufferReducer(initialState, {
+          type: 'vim_delete_line',
+          payload: { count: 1 },
+        });
+
+        // Should leave an empty line when deleting the only line
+        expect(result.lines).toEqual(['']);
+        expect(result.cursorRow).toBe(0);
+        expect(result.cursorCol).toBe(0);
+      });
+    });
+
+    describe('D (delete to end of line)', () => {
+      it('should delete from cursor to end of line', () => {
+        const initialState = {
+          lines: ['hello world test'],
+          cursorRow: 0,
+          cursorCol: 6, // cursor on 'w' in "world"
+          preferredCol: null,
+          undoStack: [],
+          redoStack: [],
+          clipboard: null,
+          selectionAnchor: null,
+        };
+
+        const result = textBufferReducer(initialState, {
+          type: 'vim_delete_to_end_of_line',
+        });
+
+        // Should delete "world test", leaving "hello "
+        expect(result.lines).toEqual(['hello ']);
+        expect(result.cursorRow).toBe(0);
+        expect(result.cursorCol).toBe(6);
+      });
+
+      it('should handle D at end of line', () => {
+        const initialState = {
+          lines: ['hello world'],
+          cursorRow: 0,
+          cursorCol: 11, // cursor at end
+          preferredCol: null,
+          undoStack: [],
+          redoStack: [],
+          clipboard: null,
+          selectionAnchor: null,
+        };
+
+        const result = textBufferReducer(initialState, {
+          type: 'vim_delete_to_end_of_line',
+        });
+
+        // Should not change anything when at end of line
+        expect(result.lines).toEqual(['hello world']);
+        expect(result.cursorRow).toBe(0);
+        expect(result.cursorCol).toBe(11);
+      });
+    });
+
+    describe('C (change to end of line)', () => {
+      it('should change from cursor to end of line', () => {
+        const initialState = {
+          lines: ['hello world test'],
+          cursorRow: 0,
+          cursorCol: 6, // cursor on 'w' in "world"
+          preferredCol: null,
+          undoStack: [],
+          redoStack: [],
+          clipboard: null,
+          selectionAnchor: null,
+        };
+
+        const result = textBufferReducer(initialState, {
+          type: 'vim_change_to_end_of_line',
+        });
+
+        // Should delete "world test", leaving "hello "
+        expect(result.lines).toEqual(['hello ']);
+        expect(result.cursorRow).toBe(0);
+        expect(result.cursorCol).toBe(6);
+      });
+
+      it('should handle C at beginning of line', () => {
+        const initialState = {
+          lines: ['hello world'],
+          cursorRow: 0,
+          cursorCol: 0,
+          preferredCol: null,
+          undoStack: [],
+          redoStack: [],
+          clipboard: null,
+          selectionAnchor: null,
+        };
+
+        const result = textBufferReducer(initialState, {
+          type: 'vim_change_to_end_of_line',
+        });
+
+        // Should delete entire line content
+        expect(result.lines).toEqual(['']);
+        expect(result.cursorRow).toBe(0);
+        expect(result.cursorCol).toBe(0);
+      });
+    });
+  });
+});