state.test.ts

import { describe, expect, it } from "vitest";
import { Signal } from "../../src/wrapper.js";

describe("Signal.State", () => {
  it("should work", () => {
    const stateSignal = new Signal.State(0);
    expect(stateSignal.get()).toEqual(0);

    stateSignal.set(10);

    expect(stateSignal.get()).toEqual(10);
  });

  describe("Comparison semantics", () => {
    it("should cache State by Object.is", () => {
      const state = new Signal.State(NaN);
      let calls = 0;
      const computed = new Signal.Computed(() => {
        calls++;
        return state.get();
      });
      expect(calls).toBe(0);
      expect(computed.get()).toBe(NaN);
      expect(calls).toBe(1);
      state.set(NaN);
      expect(computed.get()).toBe(NaN);
      expect(calls).toBe(1);
    });

    it("applies custom equality in State", () => {
      let ecalls = 0;
      const state = new Signal.State(1, {
        equals() {
          ecalls++;
          return false;
        },
      });
      let calls = 0;
      const computed = new Signal.Computed(() => {
        calls++;
        return state.get();
      });

      expect(calls).toBe(0);
      expect(ecalls).toBe(0);

      expect(computed.get()).toBe(1);
      expect(ecalls).toBe(0);
      expect(calls).toBe(1);

      state.set(1);
      expect(computed.get()).toBe(1);
      expect(ecalls).toBe(1);
      expect(calls).toBe(2);
    });
  });
});