history.test.ts

history.test.tspackages/whiteboard/src/history.test.tsraw ← src2,280 B← Back to the app
1import { describe, expect, it } from "vitest";
2import { OpStack } from "./history.js";
3 
4describe("OpStack (T-167/T-170)", () => {
5  it("push/undo/redo walk a linear history", () => {
6    const s = new OpStack(0, 10);
7    s.push(1);
8    s.push(2);
9    expect(s.present).toBe(2);
10    expect(s.canUndo()).toBe(true);
11    expect(s.canRedo()).toBe(false);
12    expect(s.undo()).toBe(1);
13    expect(s.undo()).toBe(0);
14    expect(s.canUndo()).toBe(false);
15    expect(s.undo()).toBe(0); // no-op at the floor
16    expect(s.redo()).toBe(1);
17    expect(s.redo()).toBe(2);
18    expect(s.redo()).toBe(2); // no-op at the ceiling
19  });
20 
21  it("push after undo clears the redo branch", () => {
22    const s = new OpStack("a", 10);
23    s.push("b");
24    s.push("c");
25    s.undo(); // back to b
26    s.push("d"); // new branch
27    expect(s.present).toBe("d");
28    expect(s.canRedo()).toBe(false); // "c" branch discarded
29    expect(s.undo()).toBe("b");
30    expect(s.undo()).toBe("a");
31  });
32 
33  it("is bounded: evicts oldest, reports truncation", () => {
34    const s = new OpStack(0, 3);
35    for (let i = 1; i <= 10; i++) s.push(i);
36    expect(s.present).toBe(10);
37    expect(s.depth).toBe(3); // only the last 3 past states kept (7,8,9)
38    expect(s.truncated).toBe(true);
39    // can undo back to 7 but not further
40    expect(s.undo()).toBe(9);
41    expect(s.undo()).toBe(8);
42    expect(s.undo()).toBe(7);
43    expect(s.canUndo()).toBe(false);
44  });
45 
46  it("no-op push (same reference) is ignored", () => {
47    const obj = { v: 1 };
48    const s = new OpStack(obj, 10);
49    s.push(obj); // same ref
50    expect(s.canUndo()).toBe(false);
51    expect(s.present).toBe(obj);
52  });
53 
54  it("rejects capacity < 1", () => {
55    expect(() => new OpStack(0, 0)).toThrow();
56  });
57 
58  it("reset replaces the present with NO undo step (seed/restore)", () => {
59    const s = new OpStack("a", 10);
60    s.push("b");
61    s.push("c");
62    expect(s.canUndo()).toBe(true);
63    s.reset("x"); // e.g. the server document arrived / a version was restored
64    expect(s.present).toBe("x");
65    expect(s.canUndo()).toBe(false);
66    expect(s.canRedo()).toBe(false);
67    // edits after the reset are undoable to the reset state
68    s.push("y");
69    s.undo();
70    expect(s.present).toBe("x");
71    expect(s.canUndo()).toBe(false);
72  });
73});
74