GCTC-NTGC / TalentCloud

import { act, renderHook } from "@testing-library/react-hooks";

import { FetchError } from "../../helpers/httpRequests";

import useResourceIndex, { UNEXPECTED_FORMAT_ERROR } from "./indexResourceHook";

import { getId, hasKey, mapToObject } from "../../helpers/queries";

interface TestResource {

  id: number;

  name: string;

}

describe("indexResourceHook", () => {

  afterEach((): void => {

    fetchMock.reset();

    fetchMock.restore();

  });

  const endpoint = "https://talent.test/api/test";

  describe("test initial state and initial fetch", () => {

    it("Initially returns no values and a status of 'pending'", () => {

      fetchMock.mock("*", [], {

        delay: 10,

      });

      const { result } = renderHook(() => useResourceIndex(endpoint));

      expect(result.current.values).toEqual({});

      expect(result.current.indexStatus).toEqual("pending");

    });

    it("If initial value is set, returns that value and does not automatically fetch.", () => {

      fetchMock.mock("*", []);

      const initialValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      const { result } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue }),

      );

      expect(result.current.values).toEqual({

        1: initialValue[0],

        2: initialValue[1],

      });

      expect(result.current.indexStatus).toEqual("initial");

      expect(fetchMock.called()).toBe(false);

    });

    it("If initial value is set, but forceInitialRefresh is true, returns the initial value but also fetches.", async () => {

      const initialValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      const updatedValue = [

        { id: 1, name: "one NEW" },

        { id: 2, name: "two NEW" },

        { id: 3, name: "three NEW" },

      ];

      fetchMock.mock("*", updatedValue, { delay: 5 });

      const { result, waitFor } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue, forceInitialRefresh: true }),

      );

      expect(result.current.values).toEqual(arrayToIndexedObj(initialValue));

      expect(result.current.indexStatus).toEqual("pending");

      expect(fetchMock.called()).toBe(true);

      await waitFor(() => result.current.indexStatus === "fulfilled");

      expect(result.current.values).toEqual(arrayToIndexedObj(updatedValue));

      expect(result.current.indexStatus).toEqual("fulfilled");

    });

    it("If initial value is set, all entities start with status of 'initial'", () => {

      const initialValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      const { result } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue }),

      );

      expect(result.current.entityStatus).toEqual({

        1: "initial",

        2: "initial",

      });

    });

    it("Returns new values and status of 'fulfilled' after initial fetch succeeds", async () => {

      const initialValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      fetchMock.mock("*", initialValue, {

        delay: 10,

      });

      const { result, waitFor } = renderHook(() => useResourceIndex(endpoint));

      expect(result.current.values).toEqual({});

      expect(result.current.indexStatus).toEqual("pending");

      await waitFor(

        () => {

          return result.current.indexStatus === "fulfilled";

        },

        { timeout: 100 },

      );

      expect(result.current.values).toEqual(arrayToIndexedObj(initialValue));

    });

    it("parseIndexResponse (if set) transforms values returns by index requests", async () => {

      const responseValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      const parseIndexResponse = (arr) =>

        arr.map((x) => ({ ...x, name: `${x.name} PARSED` }));

      const expectValue = [

        { id: 1, name: "one PARSED" },

        { id: 2, name: "two PARSED" },

      ];

      fetchMock.mock("*", responseValue);

      const { result, waitFor } = renderHook(() =>

        useResourceIndex(endpoint, { parseIndexResponse }),

      );

      expect(result.current.values).toEqual({});

      expect(result.current.indexStatus).toEqual("pending");

      await waitFor(() => result.current.indexStatus === "fulfilled");

      expect(result.current.values).toEqual(arrayToIndexedObj(expectValue));

    });

    it("Initial fetch is a GET request to the provided endpoint", async () => {

      fetchMock.getOnce(endpoint, []);

      const { result, waitForNextUpdate } = renderHook(() =>

        useResourceIndex(endpoint),

      );

      await waitForNextUpdate();

      expect(result.current.indexStatus).toBe("fulfilled");

      expect(fetchMock.called()).toBe(true);

    });

    it("After initial fetch, all values have entityStatus of 'fulfilled'", async () => {

      const responseValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      fetchMock.getOnce(endpoint, responseValue);

      const { result, waitFor } = renderHook(() => useResourceIndex(endpoint));

      expect(result.current.entityStatus).toEqual({});

      await waitFor(() => result.current.indexStatus === "fulfilled");

      expect(result.current.entityStatus).toEqual({

        1: "fulfilled",

        2: "fulfilled",

      });

    });

    it("Returns a 'rejected' status and calls handleError when initial fetch returns a server error", async () => {

      fetchMock.once(endpoint, 404);

      const handleError = jest.fn();

      const { result, waitForNextUpdate } = renderHook(() =>

        useResourceIndex(endpoint, { handleError }),

      );

      expect(result.current.values).toEqual({});

      expect(result.current.indexStatus).toEqual("pending");

      await waitForNextUpdate();

      expect(result.current.values).toEqual({});

      expect(result.current.indexStatus).toEqual("rejected");

      // handleError was called once on initial fetch.

      expect(handleError.mock.calls.length).toBe(1);

      // Get error from argument to mocked function.

      const initialError = handleError.mock.calls[0][0];

      expect(initialError).toBeInstanceOf(FetchError);

      expect(initialError.response.status).toBe(404);

    });

  });

  describe("test refresh callback", () => {

    it("refresh() triggers a GET request to endpoint and sets status to 'pending'", async () => {

      fetchMock.getOnce(endpoint, []);

      const { result, waitForNextUpdate } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue: [] }),

      );

      expect(result.current.indexStatus).toBe("initial");

      await act(async () => {

        result.current.refresh();

        await waitForNextUpdate({ timeout: false });

        expect(result.current.indexStatus).toEqual("pending");

      });

      expect(fetchMock.called()).toBe(true);

    });

    it("refresh() returns fetch result and updates hook value", async () => {

      const responseValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      fetchMock.mock(endpoint, responseValue);

      const { result } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue: [] }),

      );

      expect(result.current.values).toEqual({});

      expect(result.current.indexStatus).toEqual("initial");

      await act(async () => {

        const refreshValue = await result.current.refresh();

        expect(refreshValue).toEqual(responseValue);

      });

      expect(result.current.indexStatus).toEqual("fulfilled");

      expect(result.current.values).toEqual(arrayToIndexedObj(responseValue));

    });

    it("refresh() rejects with an error when fetch returns a server error", async () => {

      fetchMock.once(endpoint, 404);

      const handleError = jest.fn();

      const initialValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      const { result } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue, handleError }),

      );

      expect(result.current.values).toEqual(arrayToIndexedObj(initialValue));

      expect(result.current.indexStatus).toEqual("initial");

      await act(async () => {

        await expect(result.current.refresh()).rejects.toBeInstanceOf(

          FetchError,

        );

      });

      expect(result.current.values).toEqual(arrayToIndexedObj(initialValue));

      expect(result.current.indexStatus).toEqual("rejected");

      // handleError was called once on initial fetch.

      expect(handleError.mock.calls.length).toBe(1);

      // Get error from argument to mocked function.

      const initialError = handleError.mock.calls[0][0];

      expect(initialError).toBeInstanceOf(FetchError);

      expect(initialError.response.status).toBe(404);

    });

    it("when refresh() returns a server error, handleError is called", async () => {

      fetchMock.once("*", 404);

      const handleError = jest.fn();

      const initialValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      const { result } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue, handleError }),

      );

      await act(async () => {

        await expect(result.current.refresh()).rejects.toBeInstanceOf(

          FetchError,

        );

      });

      // handleError was called once on initial fetch.

      expect(handleError.mock.calls.length).toBe(1);

      // Get error from argument to mocked function.

      const initialError = handleError.mock.calls[0][0];

      expect(initialError).toBeInstanceOf(FetchError);

      expect(initialError.response.status).toBe(404);

    });

    it("when refresh() triggers a Fetch error, handleError is called", async () => {

      fetchMock.once("*", { throws: new Error("Failed to fetch") });

      const handleError = jest.fn();

      const initialValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      const { result } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue, handleError }),

      );

      await act(async () => {

        await expect(result.current.refresh()).rejects.toBeInstanceOf(Error);

      });

      // handleError was called once on initial fetch.

      expect(handleError.mock.calls.length).toBe(1);

      // Get error from argument to mocked function.

      const initialError = handleError.mock.calls[0][0];

      expect(initialError.message).toBe("Failed to fetch");

    });

    it("when refresh() returns invalid JSON, handleError is called", async () => {

      fetchMock.once("*", "This is the response");

      const handleError = jest.fn();

      const initialValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      const { result } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue, handleError }),

      );

      await act(async () => {

        await expect(result.current.refresh()).rejects.toBeInstanceOf(Error);

      });

      // handleError was called once on initial fetch.

      expect(handleError.mock.calls.length).toBe(1);

      // Get error from argument to mocked function.

      const initialError = handleError.mock.calls[0][0];

      expect(

        initialError.message.startsWith("invalid json response body"),

      ).toBe(true);

    });

    it("when refresh() returns an object with no id, handleError is called", async () => {

      fetchMock.once("*", [

        { id: 1, name: "one valid JSON" },

        { name: "two valid JSON but no id" },

      ]);

      const handleError = jest.fn();

      const initialValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      const { result } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue, handleError }),

      );

      await act(async () => {

        await expect(result.current.refresh()).rejects.toBeInstanceOf(Error);

      });

      // handleError was called once on initial fetch.

      expect(handleError.mock.calls.length).toBe(1);

      // Get error from argument to mocked function.

      const initialError = handleError.mock.calls[0][0];

      expect(initialError.message).toBe(UNEXPECTED_FORMAT_ERROR);

    });

    it("If refresh() is called twice, and one request returns, status remains pending", async () => {

      fetchMock.once(endpoint, [], {

        delay: 10,

      });

      // Second call will take longer.

      fetchMock.mock("*", [], {

        delay: 20,

      });

      const { result } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue: [] }),

      );

      await act(async () => {

        const refreshPromise1 = result.current.refresh();

        const refreshPromise2 = result.current.refresh();

        await refreshPromise1;

        expect(result.current.indexStatus).toEqual("pending");

        await refreshPromise2;

        expect(result.current.indexStatus).toEqual("fulfilled");

      });

    });

    it("refresh() sets status on all entities to pending, and to fulfilled when it completes", async () => {

      fetchMock.mock("*", [

        { id: 1, name: "NEW one" },

        { id: 2, name: "NEW two" },

      ]);

      const initialValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      const { result, waitForNextUpdate } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue }),

      );

      await act(async () => {

        result.current.refresh();

        await waitForNextUpdate({ timeout: false });

        expect(result.current.entityStatus).toEqual({

          1: "pending",

          2: "pending",

        });

        await waitForNextUpdate();

      });

      expect(result.current.entityStatus).toEqual({

        1: "fulfilled",

        2: "fulfilled",

      });

    });

    it("A successful refresh will overwrite a previous error state", async () => {

      const responseValue = [

        { id: 1, name: "NEW one" },

        { id: 2, name: "NEW two" },

      ];

      // First request fails, second succeeds

      fetchMock.once(endpoint, 404);

      fetchMock.mock("*", responseValue);

      const { result, waitForNextUpdate } = renderHook(() =>

        useResourceIndex(endpoint),

      );

      await waitForNextUpdate();

      expect(result.current.indexStatus).toBe("rejected");

      await act(async () => {

        await result.current.refresh();

      });

      expect(result.current.indexStatus).toBe("fulfilled");

      expect(result.current.values).toEqual(arrayToIndexedObj(responseValue));

    });

  });

  describe("test create callback", () => {

    it("create() changes createStatus from initial to pending, and to fulfilled when it completes", async () => {

      fetchMock.mock("*", { id: 1, name: "one" });

      const { result, waitForNextUpdate } = renderHook(() =>

        useResourceIndex<TestResource>(endpoint, { initialValue: [] }),

      );

      expect(result.current.createStatus).toBe("initial");

      await act(async () => {

        result.current.create({ id: 0, name: "one" });

        await waitForNextUpdate({ timeout: false });

        expect(result.current.createStatus).toBe("pending");

        await waitForNextUpdate();

        expect(result.current.createStatus).toBe("fulfilled");

      });

    });

    it("create() triggers a POST request to endpoint", async () => {

      fetchMock.postOnce(endpoint, { id: 1, name: "one" });

      const { result } = renderHook(() =>

        useResourceIndex<TestResource>(endpoint, { initialValue: [] }),

      );

      await act(async () => {

        await result.current.create({ id: 0, name: "one" });

      });

      expect(fetchMock.called()).toBe(true);

    });

    it("If resolveCreateEndpoint is set, create() triggers a POST request to the resulting endpoint", async () => {

      const resolveCreateEndpoint = (baseEndpoint, newEntity) =>

        `${baseEndpoint}/createTest/${newEntity.name}`;

      const newEntity = { id: 0, name: "one" };

      fetchMock.postOnce(resolveCreateEndpoint(endpoint, newEntity), {

        id: 1,

        name: "one",

      });

      const { result } = renderHook(() =>

        useResourceIndex<TestResource>(endpoint, {

          initialValue: [],

          resolveCreateEndpoint,

        }),

      );

      await act(async () => {

        await result.current.create(newEntity);

      });

      expect(fetchMock.called()).toBe(true);

    });

    it("create() returns fetch result and adds to values when it completes", async () => {

      const initialValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      const createValue = { id: 0, name: "three" };

      // NOTE: The value returned from server may be slightly different from what we send it - likely a different id.

      const responseValue = { id: 3, name: "three" };

      fetchMock.postOnce(endpoint, responseValue);

      const { result } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue }),

      );

      await act(async () => {

        const createResponseValue = await result.current.create(createValue);

        expect(createResponseValue).toEqual(responseValue);

      });

      // Ensure the new value is the one returned from request, not what we tried to send.

      expect(result.current.values[3]).toEqual(responseValue);

    });

    it("create() rejects with an error (leaving values unchanged) when fetch returns a server error", async () => {

      const initialValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      const createValue = { id: 3, name: "three" };

      fetchMock.postOnce("*", 404);

      const { result } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue }),

      );

      await act(async () => {

        await expect(result.current.create(createValue)).rejects.toBeInstanceOf(

          FetchError,

        );

      });

      // Values should be unchanged from initial values because create request failed, though createStatus should be different.

      expect(result.current.values).toEqual(arrayToIndexedObj(initialValue));

      expect(result.current.createStatus).toEqual("rejected");

    });

    it("when create() returns a server error, handleError is called", async () => {

      const initialValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      const createValue = { id: 3, name: "three" };

      fetchMock.postOnce("*", 404);

      const handleError = jest.fn();

      const { result } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue, handleError }),

      );

      await act(async () => {

        await expect(result.current.create(createValue)).rejects.toBeInstanceOf(

          FetchError,

        );

      });

      // handleError was called once on initial fetch.

      expect(handleError.mock.calls.length).toBe(1);

      // Get error from argument to mocked function.

      const initialError = handleError.mock.calls[0][0];

      expect(initialError).toBeInstanceOf(FetchError);

      expect(initialError.response.status).toBe(404);

    });

    it("when create() triggers a Fetch error, it is handled correctly", async () => {

      const initialValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      const createValue = { id: 3, name: "three" };

      fetchMock.postOnce("*", { throws: new Error("Failed to fetch") });

      const handleError = jest.fn();

      const { result } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue, handleError }),

      );

      await act(async () => {

        await expect(result.current.create(createValue)).rejects.toBeInstanceOf(

          Error,

        );

      });

      // Values should be unchanged from initial values because create request failed, though createStatus should be different.

      expect(result.current.values).toEqual(arrayToIndexedObj(initialValue));

      expect(result.current.createStatus).toEqual("rejected");

      // handleError was called once on initial fetch.

      expect(handleError.mock.calls.length).toBe(1);

      // Get error from argument to mocked function.

      const initialError = handleError.mock.calls[0][0];

      expect(initialError).toBeInstanceOf(Error);

      expect(initialError.message).toBe("Failed to fetch");

    });

    it("when create() returns invalid JSON, error is handled correctly", async () => {

      const initialValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      const createValue = { id: 3, name: "three" };

      fetchMock.postOnce("*", "This response is not JSON");

      const handleError = jest.fn();

      const { result } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue, handleError }),

      );

      await act(async () => {

        await expect(result.current.create(createValue)).rejects.toBeInstanceOf(

          Error,

        );

      });

      // Values should be unchanged from initial values because create request failed, though createStatus should be different.

      expect(result.current.values).toEqual(arrayToIndexedObj(initialValue));

      expect(result.current.createStatus).toEqual("rejected");

      // handleError was called once on initial fetch.

      expect(handleError.mock.calls.length).toBe(1);

      // Get error from argument to mocked function.

      const initialError = handleError.mock.calls[0][0];

      expect(initialError).toBeInstanceOf(Error);

      expect(

        initialError.message.startsWith("invalid json response body"),

      ).toBe(true);

    });

    it("when create() returns an object with an id which already exists in values, that object is updated", async () => {

      const initialValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      const duplicateValue = { id: 2, name: "UPDATED two" };

      fetchMock.postOnce("*", duplicateValue);

      const { result } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue }),

      );

      await act(async () => {

        await result.current.create(duplicateValue);

      });

      expect(result.current.values[2]).toEqual(duplicateValue);

      expect(result.current.createStatus).toEqual("fulfilled");

    });

    it("If multiple create requests are started, createStatus remains pending untill all are complete", async () => {

      const createOne = { id: 0, name: "one" };

      const createTwo = { id: 0, name: "two" };

      // NOTE: The value returned from server may be slightly different from what we send it - likely a different id.

      fetchMock.postOnce(endpoint, createOne);

      fetchMock.post("*", createTwo, { delay: 5 });

      const { result } = renderHook(() =>

        useResourceIndex<TestResource>(endpoint, { initialValue: [] }),

      );

      await act(async () => {

        const createPromise1 = result.current.create(createOne);

        const createPromise2 = result.current.create(createTwo);

        await createPromise1;

        expect(result.current.values).toEqual(arrayToIndexedObj([createOne]));

        expect(result.current.createStatus).toEqual("pending");

        await createPromise2;

        expect(result.current.values).toEqual(

          arrayToIndexedObj([createOne, createTwo]),

        );

        expect(result.current.createStatus).toEqual("fulfilled");

      });

    });

    it("A successful create() will overwrite a previous error state", async () => {

      const createOne = { id: 0, name: "one" };

      const createTwo = { id: 0, name: "two" };

      // NOTE: The value returned from server may be slightly different from what we send it - likely a different id.

      fetchMock.postOnce(endpoint, 404);

      fetchMock.post("*", createTwo, { delay: 5 });

      const { result } = renderHook(() =>

        useResourceIndex<TestResource>(endpoint, { initialValue: [] }),

      );

      await act(async () => {

        await expect(result.current.create(createOne)).rejects.toThrow();

        expect(result.current.values).toEqual({});

        expect(result.current.createStatus).toEqual("rejected");

        await result.current.create(createTwo);

        expect(result.current.values).toEqual(arrayToIndexedObj([createTwo]));

        expect(result.current.createStatus).toEqual("fulfilled");

      });

    });

  });

  describe("test update callback", () => {

    it("update() changes status of specific entity to pending, and then fulfilled, without affecting status of others", async () => {

      const initialValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      const updateValue = { id: 2, name: "UPDATE two" };

      fetchMock.mock("*", updateValue);

      const { result, waitForNextUpdate } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue }),

      );

      expect(result.current.entityStatus[2]).toEqual("initial");

      expect(result.current.entityStatus[1]).toEqual("initial");

      expect(result.current.indexStatus).toEqual("initial");

      await act(async () => {

        result.current.update(updateValue);

        await waitForNextUpdate({ timeout: false });

        expect(result.current.entityStatus[2]).toEqual("pending");

        expect(result.current.entityStatus[1]).toEqual("initial");

        expect(result.current.indexStatus).toEqual("initial");

        await waitForNextUpdate();

        expect(result.current.entityStatus[2]).toEqual("fulfilled");

        expect(result.current.entityStatus[1]).toEqual("initial");

        expect(result.current.indexStatus).toEqual("initial");

      });

    });

    it("update() triggers a PUT request to endpoint (with id appended)", async () => {

      const initialValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      const updateValue = { id: 2, name: "UPDATE two" };

      fetchMock.putOnce(`${endpoint}/${updateValue.id}`, updateValue);

      const { result } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue }),

      );

      await act(async () => {

        await result.current.update(updateValue);

      });

      expect(fetchMock.called()).toBe(true);

    });

    it("If resolveEntityEndpoint is set, update() triggers a PUT request to resulting endpoint", async () => {

      const initialValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      const updateValue = { id: 2, name: "UPDATE two" };

      const resolveEntityEndpoint = (baseEndpoint, id) =>

        `${baseEndpoint}/resolveEntityTest/${id}`;

      fetchMock.putOnce(

        resolveEntityEndpoint(endpoint, updateValue.id),

        updateValue,

      );

      const { result } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue, resolveEntityEndpoint }),

      );

      await act(async () => {

        await result.current.update(updateValue);

      });

      expect(fetchMock.called()).toBe(true);

    });

    it("update() returns fetch result and updates values when it completes", async () => {

      const initialValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      const updateValue = { id: 2, name: "UPDATE two" };

      // NOTE: The value returned from server may be slightly different from what we send it.

      const responseValue = { id: 2, name: "UPDATE two RETURNED" };

      fetchMock.putOnce("*", responseValue);

      const { result } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue }),

      );

      await act(async () => {

        const updateResponseValue = await result.current.update(updateValue);

        expect(updateResponseValue).toEqual(responseValue);

      });

      // Ensure the new value is the one returned from request, not what we tried to send.

      expect(result.current.values[2]).toEqual(responseValue);

    });

    it("update() rejects with an error (leaving values unchanged) when fetch returns a server error", async () => {

      const initialValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      const updateValue = { id: 2, name: "UPDATE two" };

      fetchMock.putOnce("*", 404);

      const { result } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue }),

      );

      await act(async () => {

        await expect(result.current.update(updateValue)).rejects.toBeInstanceOf(

          FetchError,

        );

      });

      expect(result.current.values).toEqual(arrayToIndexedObj(initialValue));

      expect(result.current.entityStatus[2]).toEqual("rejected");

    });

    it("when update() returns a server error, handleError is called", async () => {

      fetchMock.putOnce("*", 404);

      const handleError = jest.fn();

      const initialValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      const updateValue = { id: 2, name: "UPDATE two" };

      const { result } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue, handleError }),

      );

      await act(async () => {

        await expect(result.current.update(updateValue)).rejects.toBeInstanceOf(

          FetchError,

        );

      });

      // handleError was called once on initial fetch.

      expect(handleError.mock.calls.length).toBe(1);

      // Get error from argument to mocked function.

      const initialError = handleError.mock.calls[0][0];

      expect(initialError).toBeInstanceOf(FetchError);

      expect(initialError.response.status).toBe(404);

    });

    it("when update() triggers a Fetch error, error is handled correctly", async () => {

      fetchMock.putOnce("*", { throws: new Error("Failed to fetch") });

      const handleError = jest.fn();

      const initialValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      const updateValue = { id: 2, name: "UPDATE two" };

      const { result } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue, handleError }),

      );

      await act(async () => {

        await expect(result.current.update(updateValue)).rejects.toBeInstanceOf(

          Error,

        );

      });

      // handleError was called once on initial fetch.

      expect(handleError.mock.calls.length).toBe(1);

      // Get error from argument to mocked function.

      const initialError = handleError.mock.calls[0][0];

      expect(initialError.message).toBe("Failed to fetch");

    });

    it("when update() is called with an object whose id doesn't exist yet, state is unchanged until update request is fulfilled", async () => {

      const initialValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      const newValue = { id: 3, name: "three" };

      fetchMock.putOnce("*", newValue);

      const { result, waitForNextUpdate } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue }),

      );

      await act(async () => {

        result.current.update(newValue);

        await waitForNextUpdate({ timeout: false });

        expect(result.current.values).toEqual(arrayToIndexedObj(initialValue));

        await waitForNextUpdate();

        expect(result.current.values[3]).toEqual(newValue);

        expect(result.current.entityStatus[3]).toEqual("fulfilled");

      });

    });

    it("when update() returns invalid JSON, error is handled correctly", async () => {

      fetchMock.putOnce("*", "This is the response");

      const handleError = jest.fn();

      const initialValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      const updateValue = { id: 2, name: "UPDATE two" };

      const { result } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue, handleError }),

      );

      await act(async () => {

        await expect(result.current.update(updateValue)).rejects.toBeInstanceOf(

          Error,

        );

      });

      // handleError was called once on initial fetch.

      expect(handleError.mock.calls.length).toBe(1);

      // Get error from argument to mocked function.

      const initialError = handleError.mock.calls[0][0];

      expect(

        initialError.message.startsWith("invalid json response body"),

      ).toBe(true);

    });

    it("when update() returns an object with no id, error is handled correctly", async () => {

      fetchMock.putOnce("*", { name: "This is valid JSON now" });

      const handleError = jest.fn();

      const initialValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      const updateValue = { id: 2, name: "UPDATE two" };

      const { result } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue, handleError }),

      );

      await act(async () => {

        await expect(result.current.update(updateValue)).rejects.toBeInstanceOf(

          Error,

        );

      });

      // handleError was called once on initial fetch.

      expect(handleError.mock.calls.length).toBe(1);

      // Get error from argument to mocked function.

      const initialError = handleError.mock.calls[0][0];

      expect(initialError.message).toBe(UNEXPECTED_FORMAT_ERROR);

    });

    it("If multiple update requests are started, status remains pending until all are complete", async () => {

      const response1 = { id: 2, name: "UPDATE two v1" };

      const response2 = { id: 2, name: "UPDATE two v2" };

      fetchMock.once(`${endpoint}/2`, response1);

      // Second call will take longer.

      fetchMock.mock("*", response2, {

        delay: 5,

      });

      const initialValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      const updateValue = { id: 2, name: "UPDATE two" };

      const { result } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue }),

      );

      await act(async () => {

        const updatePromise1 = result.current.update(updateValue);

        const updatePromise2 = result.current.update(updateValue);

        await updatePromise1;

        expect(result.current.values[2]).toEqual(response1);

        expect(result.current.entityStatus[2]).toEqual("pending");

        await updatePromise2;

        expect(result.current.values[2]).toEqual(response2);

        expect(result.current.entityStatus[2]).toEqual("fulfilled");

      });

    });

    it("A successful update() will overwrite a previous error state", async () => {

      const initialValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      const updateValue = { id: 2, name: "UPDATE two" };

      // First request fails, second succeeds

      fetchMock.putOnce(`${endpoint}/${updateValue.id}`, 404);

      fetchMock.mock("*", updateValue);

      const { result } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue }),

      );

      await act(async () => {

        expect(result.current.update(updateValue)).rejects.toBeInstanceOf(

          FetchError,

        );

      });

      expect(result.current.entityStatus[2]).toBe("rejected");

      await act(async () => {

        await result.current.update(updateValue);

      });

      expect(result.current.entityStatus[2]).toBe("fulfilled");

      expect(result.current.values[2]).toEqual(updateValue);

    });

  });

  describe("test deleteResource callback", () => {

    it("deleteResource() changes status of specific entity from initial to pending. Status and value are removed when it completes.", async () => {

      const initialValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      fetchMock.mock("*", 200, { delay: 5 });

      const { result, waitForNextUpdate } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue }),

      );

      expect(result.current.entityStatus[2]).toEqual("initial");

      expect(result.current.entityStatus[1]).toEqual("initial");

      expect(result.current.indexStatus).toEqual("initial");

      await act(async () => {

        result.current.deleteResource(2);

        await waitForNextUpdate();

        expect(result.current.entityStatus[2]).toEqual("pending");

        expect(result.current.entityStatus[1]).toEqual("initial");

        expect(result.current.indexStatus).toEqual("initial");

        await waitForNextUpdate();

        expect(hasKey(result.current.entityStatus, 2)).toBe(false);

        expect(hasKey(result.current.values, 2)).toBe(false);

        expect(result.current.entityStatus[1]).toEqual("initial");

        expect(result.current.indexStatus).toEqual("initial");

      });

    });

    it("deleteResource() triggers a DELETE request to endpoint with id appended", async () => {

      const initialValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      fetchMock.deleteOnce(`${endpoint}/2`, 200);

      const { result } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue }),

      );

      await act(async () => {

        await result.current.deleteResource(2);

      });

      expect(fetchMock.called()).toBe(true);

    });

    it("If resolveEntityEndpoint is set, deleteResource() triggers a DELETE request to resulting endpoint", async () => {

      const initialValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      const resolveEntityEndpoint = (baseEndpoint, id) =>

        `${baseEndpoint}/resolveEntityTest/${id}`;

      fetchMock.deleteOnce(resolveEntityEndpoint(endpoint, 2), 200);

      const { result } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue, resolveEntityEndpoint }),

      );

      await act(async () => {

        await result.current.deleteResource(2);

      });

      expect(fetchMock.called()).toBe(true);

    });

    it("deleteResource() resolves when entity is removed from values", async () => {

      const initialValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      fetchMock.mock("*", 200, { delay: 5 });

      const { result } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue }),

      );

      await act(async () => {

        await result.current.deleteResource(2);

        expect(hasKey(result.current.entityStatus, 2)).toBe(false);

        expect(hasKey(result.current.values, 2)).toBe(false);

      });

    });

    it("deleteResource() rejects with an error (leaving values unchanged) when fetch returns a server error", async () => {

      const initialValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      fetchMock.deleteOnce("*", 404);

      const { result } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue }),

      );

      await act(async () => {

        await expect(result.current.deleteResource(2)).rejects.toBeInstanceOf(

          FetchError,

        );

      });

      expect(result.current.values).toEqual(arrayToIndexedObj(initialValue));

      expect(result.current.entityStatus[2]).toEqual("rejected");

    });

    it("when deleteResource() returns a server error, handleError is called", async () => {

      fetchMock.deleteOnce("*", 500);

      const handleError = jest.fn();

      const initialValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      const { result } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue, handleError }),

      );

      await act(async () => {

        await expect(result.current.deleteResource(2)).rejects.toBeInstanceOf(

          FetchError,

        );

      });

      // handleError was called once on initial fetch.

      expect(handleError.mock.calls.length).toBe(1);

      // Get error from argument to mocked function.

      const initialError = handleError.mock.calls[0][0];

      expect(initialError).toBeInstanceOf(FetchError);

      expect(initialError.response.status).toBe(500);

    });

    it("when deleteResource() triggers a Fetch error, handleError is called", async () => {

      fetchMock.deleteOnce("*", { throws: new Error("Failed to fetch") });

      const handleError = jest.fn();

      const initialValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      const { result } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue, handleError }),

      );

      await act(async () => {

        await expect(result.current.deleteResource(2)).rejects.toBeInstanceOf(

          Error,

        );

      });

      // handleError was called once on initial fetch.

      expect(handleError.mock.calls.length).toBe(1);

      // Get error from argument to mocked function.

      const initialError = handleError.mock.calls[0][0];

      expect(initialError).toBeInstanceOf(Error);

      expect(initialError).toEqual(new Error("Failed to fetch"));

    });

    it("if deleteResource() is called multiple times on the same id, status should remain pending until one succeeds. Later callbacks should not change values.", async () => {

      const initialValue = [

        { id: 1, name: "one" },

        { id: 2, name: "two" },

      ];

      // First call will fail, subsequent calls will succeed.

      fetchMock.deleteOnce(`${endpoint}/2`, 500);

      fetchMock.delete("*", 200, { delay: 5 });

      const { result } = renderHook(() =>

        useResourceIndex(endpoint, { initialValue }),

      );

      await act(async () => {

        const deletePromise1 = result.current.deleteResource(2);

        const deletePromise2 = result.current.deleteResource(2);

        const deletePromise3 = result.current.deleteResource(2);

        await expect(deletePromise1).rejects.toThrow();

        expect(result.current.entityStatus[2]).toBe("pending");

        await deletePromise2;

        const expectValue = { 1: { id: 1, name: "one" } };

        expect(result.current.values).toEqual(expectValue);

        await deletePromise3;

        expect(result.current.values).toEqual(expectValue);

      });

    });

  });

});