testing/src/mock.test.ts

import { describe, it } from "./blocks.ts";
import { expect } from "./assertions.ts";
import { mock, mockfn, patch } from "./mock.ts";

class Obj {
  called = 0;
  func(x: number) {
    this.called += 1;
    return x * 2;
  }
}

function checkRestored(o: Obj) {
  const called = o.called;
  const result = o.func(4);
  expect(o.called).toEqual(called + 1);
  expect(result).toEqual(8);
}

describe("patch", () => {
  it("calls through by default", () => {
    const o = new Obj();

    patch(o, "func", (mock) => {
      const result = o.func(3);
      expect(o.called).toEqual(1);
      expect(result).toEqual(6);
      expect(mock).toHaveBeenCalledTimes(1);
      expect(mock).toHaveBeenCalledWith(3);
    });

    patch(o, "func", (mock) => {
      const result = o.func(1);
      expect(o.called).toEqual(2);
      expect(result).toEqual(2);
      expect(mock).toHaveBeenCalledTimes(1);
      expect(mock).toHaveBeenCalledWith(1);
    });

    checkRestored(o);
  });

  it("calls sequential stubs before passing through", () => {
    const o = new Obj();

    patch(o, "func", (mock) => {
      mock.stub((a) => a * 3);
      mock.stub((a) => a * 4);

      let result = o.func(2);
      expect(result).toEqual(6);

      result = o.func(2);
      expect(result).toEqual(8);

      expect(o.called).toEqual(0);

      result = o.func(2);
      expect(result).toEqual(4);

      expect(o.called).toEqual(1);
      expect(mock).toHaveBeenCalledTimes(3);
    });

    checkRestored(o);
  });

  it("calls stubs in loop", () => {
    const o = new Obj();

    patch(o, "func", (mock) => {
      mock.stub((a) => a * 3, true);
      let result = o.func(2);
      expect(result).toEqual(6);

      result = o.func(2);
      expect(result).toEqual(6);

      result = o.func(2);
      expect(result).toEqual(6);

      expect(o.called).toEqual(0);
      expect(mock).toHaveBeenCalledTimes(3);
    });

    checkRestored(o);
  });

  it("can reset the mock", () => {
    const o = new Obj();

    patch(o, "func", (mock) => {
      mock.stub((a) => a + 1, true);
      let result = o.func(3);
      expect(o.called).toEqual(0);
      expect(result).toEqual(4);
      expect(mock).toHaveBeenCalledTimes(1);
      expect(mock).toHaveBeenCalledWith(3);

      result = o.func(2);
      expect(o.called).toEqual(0);
      expect(result).toEqual(3);
      expect(mock).toHaveBeenCalledTimes(2);
      expect(mock).toHaveBeenCalledWith(2);

      mock.reset();
      mock.stub((a) => a + 10, true);

      result = o.func(4);
      expect(o.called).toEqual(0);
      expect(result).toEqual(14);
      expect(mock).toHaveBeenCalledTimes(1);
      expect(mock).toHaveBeenCalledWith(4);

      mock.reset();

      result = o.func(4);
      expect(o.called).toEqual(1);
      expect(result).toEqual(8);
      expect(mock).toHaveBeenCalledTimes(1);
      expect(mock).toHaveBeenCalledWith(4);
    });

    checkRestored(o);
  });
});

describe("mock", () => {
  it("puts a no-op stub by default", () => {
    const o = new Obj();

    mock(o, "func", undefined, (mock) => {
      let result = o.func(2);
      expect(result).toBeUndefined();

      expect(o.called).toEqual(0);
      expect(mock).toHaveBeenCalledTimes(1);
    });

    checkRestored(o);

    const f = mock(o, "func", undefined, () => o.func(2));
    expect(f).toHaveBeenCalledTimes(1);

    checkRestored(o);
  });

  it("stubs with a fixed value", () => {
    const o = new Obj();

    mock(o, "func", 17, (mock) => {
      let result = o.func(2);
      expect(result).toBe(17);

      result = o.func(2);
      expect(result).toBe(17);

      expect(o.called).toEqual(0);
      expect(mock).toHaveBeenCalledTimes(2);
    });

    checkRestored(o);
  });

  it("stubs with a function result", () => {
    const o = new Obj();

    let i = 9;
    mock(o, "func", () => ++i, (mock) => {
      let result = o.func(2);
      expect(result).toBe(10);

      result = o.func(2);
      expect(result).toBe(11);

      expect(o.called).toEqual(0);
      expect(mock).toHaveBeenCalledTimes(2);
    });

    checkRestored(o);
  });
});

describe("mockfn", () => {
  it("constructs a simple mock function", () => {
    let mock = mockfn();
    expect(mock).toHaveBeenCalledTimes(0);
    mock();
    expect(mock).toHaveBeenCalledTimes(1);

    mock = mockfn(() => 2);
    expect(mock).toHaveBeenCalledTimes(0);
    let result = mock();
    expect(result).toEqual(2);
    expect(mock).toHaveBeenCalledTimes(1);
    result = mock();
    expect(result).toEqual(2);
    expect(mock).toHaveBeenCalledTimes(2);

    mock = mockfn((x: number) => x + 1);
    result = mock(5);
    expect(result).toEqual(6);
    expect(mock).toHaveBeenCalledTimes(1);
    expect(mock).toHaveBeenCalledWith(5);
  });
});