Unit testing TypeScript code by creating a mock of the third-party library, ioredis

Question

Unit testing TypeScript code by creating a mock of the third-party library, ioredis

Struggling to mock a third party library in typescript tests is proving to be quite a challenge.

Currently, I am developing a library based on the foundation of the typescript-starter library that utilizes ava for testing.

Specifically, I am attempting to mock the primary class of ioredis to prevent my tests from establishing real database connections.

Various attempts have been made using different mocking libraries such as sinon, testdouble.js, and mockery.

For instance, in sinon, I experimented with the following:

let redisStub = sinon.stub(IORedis)
sinon.assert.called(redisStub.Cluster)

Using testdouble, I tried various strategies, such as:

td.replace('ioredis') // #1
td.replace('./homeMadeIoredisWrapperClass') // #2

Additionally, I explored the use of mockery

mockery.enable()
mockery.registerMock('ioredis', {some: 'object'})

Despite multiple attempts, including always using require('ioredis') in the methods, the challenge persists.

Could it be that I am attempting the impossible? Mocking a database seems to be a common practice, yet the solution eludes me. Perhaps my approach is flawed, and I am targeting the wrong elements for mocking?

Any guidance on this matter would be greatly appreciated!

Ps. For context, I am striving to develop a straightforward ioredis connection wrapper.

typescript mocking sinon testdoublejs

Answer 1

Answer №1

If you need to mimic ioredis (version 4.16.2), you can achieve this using sinon. The key is to mock the connect method.

import ioredis from "ioredis";

sinon.stub(ioredis.prototype, "connect").returns(Promise.resolve());
sinon.stub(ioredis.prototype, "get").returns(Promise.resolve({ data: "hello" }));

Answer 2

If you need to mimic ioredis (version 4.16.2), you can achieve this using sinon. The key is to mock the connect method.

import ioredis from "ioredis";

sinon.stub(ioredis.prototype, "connect").returns(Promise.resolve());
sinon.stub(ioredis.prototype, "get").returns(Promise.resolve({ data: "hello" }));

Answer 3

Answer №2

After encountering a few misunderstandings and issues in my code, I stumbled upon some valuable insights that may benefit others facing similar challenges:

One issue I faced was importing "everything" (
```
import { MyLibrary } from "myLibrary"
```
) before the td.replace, causing the replacement statement to execute after the module had been required. This was due to the specific design of the example tests in the typescript-starter repository. I have addressed this issue by submitting a PR to resolve the underlying problem.
Another challenge arose from running the ava tests in parallel, leading to td.reset() occurring before some callbacks were triggered, thereby hindering the functionality of replace in certain scenarios. To overcome this, I switched to using test.serial(... in place of test(... in ava. Although this may slow down the test execution, it ensures their proper functioning. Creating separate files for each test enables true parallel runs in ava.

Additionally, I discovered some helpful wiki entries on the testdouble GitHub page: https://github.com/testdouble/contributing-tests/wiki/Don%27t-mock-what-you-don%27t-own https://github.com/testdouble/contributing-tests/wiki/SAFE-test

I trust that these insights will prove beneficial to someone in a similar situation.

Answer 4

After encountering a few misunderstandings and issues in my code, I stumbled upon some valuable insights that may benefit others facing similar challenges:

One issue I faced was importing "everything" (
```
import { MyLibrary } from "myLibrary"
```
) before the td.replace, causing the replacement statement to execute after the module had been required. This was due to the specific design of the example tests in the typescript-starter repository. I have addressed this issue by submitting a PR to resolve the underlying problem.
Another challenge arose from running the ava tests in parallel, leading to td.reset() occurring before some callbacks were triggered, thereby hindering the functionality of replace in certain scenarios. To overcome this, I switched to using test.serial(... in place of test(... in ava. Although this may slow down the test execution, it ensures their proper functioning. Creating separate files for each test enables true parallel runs in ava.

Additionally, I discovered some helpful wiki entries on the testdouble GitHub page: https://github.com/testdouble/contributing-tests/wiki/Don%27t-mock-what-you-don%27t-own https://github.com/testdouble/contributing-tests/wiki/SAFE-test

I trust that these insights will prove beneficial to someone in a similar situation.

Unit testing TypeScript code by creating a mock of the third-party library, ioredis

Answer №1

Answer №2

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