import UndoStack from "../src/undo-stack"; describe("UndoStack", function UndoStackSpecs() { beforeEach(() => { this.undoManager = new UndoStack(); }); afterEach(() => { advanceClock(500); }) describe("undo", () => { it("can restore history items, and returns null when none are available", () => { this.undoManager.save("A") this.undoManager.save("B") this.undoManager.save("C") expect(this.undoManager.current()).toBe("C") expect(this.undoManager.undo()).toBe("B") expect(this.undoManager.current()).toBe("B") expect(this.undoManager.undo()).toBe("A") expect(this.undoManager.current()).toBe("A") expect(this.undoManager.undo()).toBe(null) expect(this.undoManager.current()).toBe("A") }); it("limits the undo stack to the MAX_HISTORY_SIZE", () => { this.undoManager._MAX_STACK_SIZE = 3 this.undoManager.save("A") this.undoManager.save("B") this.undoManager.save("C") this.undoManager.save("D") expect(this.undoManager.current()).toBe("D") expect(this.undoManager.undo()).toBe("C") expect(this.undoManager.undo()).toBe("B") expect(this.undoManager.undo()).toBe(null) expect(this.undoManager.current()).toBe("B") }); }); describe("undo followed by redo", () => { it("can restore previously undone history items", () => { this.undoManager.save("A") this.undoManager.save("B") this.undoManager.save("C") expect(this.undoManager.current()).toBe("C") expect(this.undoManager.undo()).toBe("B") expect(this.undoManager.current()).toBe("B") expect(this.undoManager.redo()).toBe("C") expect(this.undoManager.current()).toBe("C") }); it("cannot be used after pushing additional items", () => { this.undoManager.save("A") this.undoManager.save("B") this.undoManager.save("C") expect(this.undoManager.current()).toBe("C") expect(this.undoManager.undo()).toBe("B") this.undoManager.save("D") expect(this.undoManager.redo()).toBe(null) expect(this.undoManager.current()).toBe("D") }); }); });