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Testing PDF Editor Command Management in Mozilla PDF.js

This test suite evaluates the CommandManager functionality in Mozilla’s PDF.js editor component. It focuses on validating undo/redo operations and command stack management for PDF editing capabilities.

Test Coverage Overview

The test suite provides comprehensive coverage of the CommandManager’s core functionality, focusing on command execution and state management.

Tests undo/redo operations sequence accuracy
Validates command stack size limitations
Verifies state consistency after multiple operations
Tests boundary conditions for maximum stack size

Implementation Analysis

The testing approach utilizes Jasmine’s describe/it pattern for behavioral testing. It implements a command pattern with reversible operations through cmd/undo function pairs.

Uses command pattern for operation management
Implements state tracking via closure variables
Employs factory functions for test command generation

Technical Details

Testing Framework: Jasmine
Test Environment: JavaScript Unit Testing
Key Classes: CommandManager
Configuration: Maximum stack size parameter
Test Utilities: makeDoUndo factory function

Best Practices Demonstrated

The test suite exemplifies several testing best practices for command-based operations.

Isolated state management
Clear test case organization
Comprehensive edge case coverage
Consistent state verification
Modular test setup

mozilla/pdfJs

test/unit/editor_spec.js

            
/* Copyright 2022 Mozilla Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import { CommandManager } from "../../src/display/editor/tools.js";

describe("editor", function () {
  describe("Command Manager", function () {
    it("should check undo/redo", function () {
      const manager = new CommandManager(4);
      let x = 0;
      const makeDoUndo = n => ({ cmd: () => (x += n), undo: () => (x -= n) });

      manager.add({ ...makeDoUndo(1), mustExec: true });
      expect(x).toEqual(1);

      manager.add({ ...makeDoUndo(2), mustExec: true });
      expect(x).toEqual(3);

      manager.add({ ...makeDoUndo(3), mustExec: true });
      expect(x).toEqual(6);

      manager.undo();
      expect(x).toEqual(3);

      manager.undo();
      expect(x).toEqual(1);

      manager.undo();
      expect(x).toEqual(0);

      manager.undo();
      expect(x).toEqual(0);

      manager.redo();
      expect(x).toEqual(1);

      manager.redo();
      expect(x).toEqual(3);

      manager.redo();
      expect(x).toEqual(6);

      manager.redo();
      expect(x).toEqual(6);

      manager.undo();
      expect(x).toEqual(3);

      manager.redo();
      expect(x).toEqual(6);
    });
  });

  it("should hit the limit of the manager", function () {
    const manager = new CommandManager(3);
    let x = 0;
    const makeDoUndo = n => ({ cmd: () => (x += n), undo: () => (x -= n) });

    manager.add({ ...makeDoUndo(1), mustExec: true }); // 1
    manager.add({ ...makeDoUndo(2), mustExec: true }); // 3
    manager.add({ ...makeDoUndo(3), mustExec: true }); // 6
    manager.add({ ...makeDoUndo(4), mustExec: true }); // 10
    expect(x).toEqual(10);

    manager.undo();
    manager.undo();
    expect(x).toEqual(3);

    manager.undo();
    expect(x).toEqual(1);

    manager.undo();
    expect(x).toEqual(1);

    manager.redo();
    manager.redo();
    expect(x).toEqual(6);
    manager.add({ ...makeDoUndo(5), mustExec: true });
    expect(x).toEqual(11);
  });
});