Mocking

Introduction

Request Mocking is a feature that allows for stubbing/mocking the response for a given endpoint, keeping the complete request lifecycle and events.

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Initialization

You can mock the response via the request.setMock method:

const mockedRequest = request.setMock({ data: { test: 1, array: [200, 300, 404] } });

This way, the mockedRequest will always return the data with value { test: 1, array: [200, 300, 404] } }. The setMock method accepts an object with the following keys:

• data - data to be returned from request
• status - Sets the response status. This can be a number or a string; the default is **200**.
• success - Informs if the request should be successful or not; the default is **true**.
• config - Sets additional parameters that tweak the mock even further.

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Config

The setMock method accepts the config object, which allows for tweaking our response.

    const request = client
      .createRequest()({ endpoint: "shared-base-endpoint" })
      .setMock({
        data: {mocking: 'is fun'},
        status: 200,
        config: {
          requestTime: 40,
          responseTime: 60,
          totalUploaded: 1000,
          totalDownloaded: 1000,
        },
      });

• timeout - boolean - informs whether it should return a timeout error.
• requestTime - Simulates how long the request to the server should take (in milliseconds).
• responseTime - Indicates how long the response from the server should take (in milliseconds). If their combined total takes longer than provided timeout, each value will be automatically adjusted to last half of the timeout time.
• totalUploaded - total number of 'kilobytes' to be uploaded.
• totalDownloaded - total number of 'kilobytes' to be downloaded.

In the example above - the request phase will take 40 milliseconds and during this phase 1000 'kilobytes' will be uploaded (and onUploadProgress events will be emitted). The response phase will take 60 millisecond and during this phase 1000 'kilobytes' will be downloaded (and onDownloadProgress events will be emitted). The word kilobytes is written in quotation marks as no real data exchange occurs - it is simply to mock events and allow for data stream mocking.

Usage and use cases

The mocker can be used in a few ways.

1. It can accept an object:

const mockedRequest = request.setMock({ data: { test: 1, array: [200, 300, 404] } });  // Always returns data: { test: 1, array: [200, 300, 404]

2. It can accept an array of values. In this case, values will be iterated over cyclically and applied each time a request is executed:

  request.setMock([
    { data: { data: [1, 2, 3] }, config: { status: 400, success: false } },
    { data: { data: [1, 2, 3] }, config: { status: 200 } },
  ]);

await request.send() // returns  { data: { data: [1, 2, 3] }, config: { status: 400, success: false } }
await request.send() // returns  { data: { data: [1, 2, 3] }, config: { status: 200 } }
await request.send() // returns  { data: { data: [1, 2, 3] }, config: { status: 400, success: false } }

3. It also accepts methods that have access to the request itself. This allows for dynamic mocking, dependent on the passed arguments during execution:

    const mockedRequest = client
      .createRequest()({ endpoint: "/users/:id" })
      .setMock((r) => {
        const { params } = r;
        if (params.id === 11) {
          return { data: [1, 2, 3], config: { status: 222 } };
        }
        return { data: [4, 5, 6] };
      });

4. The passed method may be asynchronous:

    const mockedRequest = client
      .createRequest<Record<string, any>>()({ endpoint: "users/:id" })
      .setMock(async (r) => {
        if (r?.params?.id === 1) {
          return { data: [1, 2, 3], config: { status: 222 } };
        }
        return { data: [4, 5, 6] };
      });

You can also pass a list of functions; the mocker will cycle over them and execute the correct one each time a request is executed.

Removal

If you need to remove the mocker from a request, use the removeMock method. This way mocker is disabled and mock data is removed.

mockedRequest.removeMock();

Disabling single mocker

Instead of removing mocker, you can also disable mocker and enable mocker at will with the request.setEnableMocking method. This way if you set mocking data, it will be kept and not removed as in the removeMock case.

const mockedRequest = request.setMock({ data: fixture }); // mock is set
... // Here mocker works as usual
mockedRequest.setEnableMocking(false); // Mocker is disabled
... // Request works as usual
mockedRequest.setEnableMocking(true); // Mocker is enabled once again

Disabling mocking for all requests

If you want to disable mocking for all requests of a given client instance - you can use the client.setEnableMocking method. This way all related requests will behave 'as usual' and setting/enabling mocks on single requests will not have any effect.

const client = new Client(...);
const mockedRequest_1 = newClient.createRequest()({ ... }).setMock({ data: fixture1 });
const mockedRequest_2 = newClient.createRequest()({ ... }).setMock({ data: fixture2 });
... // Here mocked requests return mocked data.
client.setEnableMocking(false) // All mocks are disabled
... // Here requests work as usual
client.setEnableMocking(true) // All mocks are enabled once again