excalidraw/src/math.test.ts

import { rotate } from "./math";

describe("rotate", () => {
  it("should rotate over (x2, y2) and return the rotated coordinates for (x1, y1)", () => {
    const x1 = 10;
    const y1 = 20;
    const x2 = 20;
    const y2 = 30;
    const angle = Math.PI / 2;
    const [rotatedX, rotatedY] = rotate(x1, y1, x2, y2, angle);
    expect([rotatedX, rotatedY]).toEqual([30, 20]);
    const res2 = rotate(rotatedX, rotatedY, x2, y2, -angle);
    expect(res2).toEqual([x1, x2]);
  });
});