jest-mock vs sinon vs testdouble
JavaScript Mocking Libraries Comparison
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What's JavaScript Mocking Libraries?

Mocking libraries in JavaScript are tools that allow developers to create mock objects, functions, or modules in their tests. These mocks simulate the behavior of real objects in a controlled way, enabling developers to isolate and test specific parts of their code without relying on external dependencies. Mocking is particularly useful for testing functions that interact with APIs, databases, or other external systems, as it allows for predictable and repeatable tests. Popular mocking libraries include jest-mock, sinon, and testdouble, each offering unique features and capabilities for creating mocks, stubs, and spies in JavaScript applications.

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jest-mock42,518,503
45,02555.4 kB2532 months agoMIT
sinon8,264,282
9,7392.08 MB463 months agoBSD-3-Clause
testdouble170,096
1,428465 kB34a year agoMIT
Feature Comparison: jest-mock vs sinon vs testdouble

Integration with Testing Frameworks

  • jest-mock:

    jest-mock is tightly integrated with the Jest testing framework, making it the best choice for projects that already use Jest. It leverages Jest's features, such as snapshot testing and parallel test execution, to provide a seamless mocking experience.

  • sinon:

    sinon is framework-agnostic and can be used with any testing framework, including Mocha, Jasmine, and Jest. This makes it a versatile choice for projects that may not be tied to a specific testing tool.

  • testdouble:

    testdouble is also framework-agnostic, but it is designed to work well with modern JavaScript and encourages a clean, declarative style of testing. It can be easily integrated into any testing setup.

API Design

  • jest-mock:

    jest-mock provides a simple and intuitive API for creating mocks and spies. Its design is focused on ease of use, with clear documentation and examples that make it easy for developers to get started quickly.

  • sinon:

    sinon offers a more comprehensive API that provides detailed control over mocking, stubbing, and spying. While it may have a steeper learning curve, its flexibility and power make it worth the investment for complex testing scenarios.

  • testdouble:

    testdouble features a clean and minimalist API that reduces boilerplate code and emphasizes readability. It encourages developers to write clear and concise tests, making it a great choice for teams that value simplicity.

Mocking Capabilities

  • jest-mock:

    jest-mock excels at mocking functions and modules, with built-in support for mocking timers and handling asynchronous code. It provides automatic mocking features that can simplify the process of creating mocks, especially for large codebases.

  • sinon:

    sinon is known for its powerful and flexible mocking capabilities, including support for deep mocking, partial mocking, and creating fake timers. It allows for fine-grained control over how functions behave during tests, making it ideal for complex scenarios.

  • testdouble:

    testdouble focuses on creating high-quality mocks and stubs with minimal effort. It encourages best practices in mocking and provides tools to create realistic doubles without the need for extensive configuration.

Community and Ecosystem

  • jest-mock:

    jest-mock benefits from the large and active Jest community, which contributes to its ongoing development and provides a wealth of resources, plugins, and integrations. This makes it a reliable choice for projects that want to stay up-to-date with the latest testing trends.

  • sinon:

    sinon has a long-established community and a rich ecosystem of plugins and extensions. Its maturity and stability make it a trusted choice for projects that require robust mocking capabilities.

  • testdouble:

    testdouble is a newer library with a growing community that values simplicity and good design. While it may not have as many plugins as Jest or Sinon, its focus on quality and usability makes it a promising choice for modern projects.

Code Example

  • jest-mock:

    Mocking a function with jest-mock

    const myFunction = jest.fn();
myFunction.mockReturnValue(42);
console.log(myFunction()); // 42
  • sinon:

    Mocking a function with sinon

    const sinon = require('sinon');
const myFunction = sinon.stub();
myFunction.returns(42);
console.log(myFunction()); // 42
  • testdouble:

    Mocking a function with testdouble

    import td from 'testdouble';
const myFunction = td.function();
td.when(myFunction()).thenReturn(42);
console.log(myFunction()); // 42
How to Choose: jest-mock vs sinon vs testdouble
  • jest-mock:

    Choose jest-mock if you are already using Jest as your testing framework and need a simple, integrated solution for mocking functions, modules, and timers. It offers a straightforward API and is optimized for use with Jest's testing environment.

  • sinon:

    Choose sinon if you need a standalone library that provides powerful and flexible mocking, stubbing, and spying capabilities. It works well with any testing framework and is ideal for projects that require fine-grained control over how functions behave during tests.

  • testdouble:

    Choose testdouble if you want a modern, minimalist approach to mocking that emphasizes simplicity and readability. It encourages good testing practices and provides a clean API for creating doubles (mocks, stubs, and spies) without a lot of boilerplate code.

Similar Npm Packages to jest-mock

jest-mock is a powerful mocking library that is part of the Jest testing framework. It allows developers to create mock functions, which can be used to simulate the behavior of real functions in tests. This is particularly useful for isolating components and testing them without relying on external dependencies. With jest-mock, you can easily track calls to functions, control their return values, and assert how they were called, making it an essential tool for unit testing in JavaScript applications.

While jest-mock is a popular choice for mocking in Jest tests, there are other libraries that offer similar functionality. Here are a few alternatives:

  • sinon is a standalone library that provides spies, stubs, and mocks for JavaScript testing. It is framework-agnostic, meaning it can be used with any testing framework, including Mocha, Jasmine, and QUnit. Sinon is known for its powerful and flexible API, allowing developers to create complex mocks and stubs with ease. If you need a comprehensive mocking solution that can be integrated into various testing frameworks, Sinon is a great choice.
  • testdouble is another mocking library that focuses on simplicity and ease of use. It provides a clean and intuitive API for creating test doubles, which can be used to replace real functions and objects in tests. Testdouble is designed to work well with any testing framework and emphasizes a straightforward approach to mocking. If you prefer a minimalistic and user-friendly mocking library, testdouble might be the right fit for your project.

To see how jest-mock compares with sinon and testdouble, check out the comparison: Comparing jest-mock vs sinon vs testdouble.

Similar Npm Packages to sinon

sinon is a powerful standalone library for creating spies, mocks, and stubs in JavaScript applications. It is primarily used for testing purposes, allowing developers to replace parts of their code with controlled replacements that can simulate behaviors and track interactions. This makes it easier to test functions in isolation without relying on their dependencies. While sinon is a robust tool for testing, there are several alternatives in the JavaScript ecosystem that also provide testing capabilities. Here are a few notable alternatives:

  • chai is an assertion library for Node.js and browsers that can be paired with any testing framework. It provides a variety of assertion styles, including BDD (Behavior-Driven Development) and TDD (Test-Driven Development) styles, making it flexible for different testing preferences. While chai does not provide mocking or spying capabilities like sinon, it can be used alongside sinon to create comprehensive tests that include assertions and mocks.
  • jasmine is a behavior-driven development framework for testing JavaScript code. It comes with built-in support for spies, mocks, and assertions, making it a complete testing solution. Jasmine is particularly known for its easy-to-read syntax and ability to run tests in any JavaScript environment. If you prefer an all-in-one testing framework that includes mocking capabilities, jasmine is a solid choice.
  • jest is a popular testing framework developed by Facebook, known for its simplicity and powerful features. Jest includes built-in support for mocking, spying, and assertions, making it a comprehensive solution for testing JavaScript applications. It also offers features like snapshot testing and parallel test execution, which can significantly speed up the testing process. If you're looking for a modern testing framework that integrates well with React and other JavaScript libraries, jest is highly recommended.
  • mocha is a flexible testing framework that allows developers to choose their assertion library and mocking tools. While mocha itself does not provide built-in mocking capabilities, it can be easily integrated with sinon for spying and stubbing. Mocha's flexibility makes it a popular choice for developers who want to customize their testing setup according to their specific needs.

To see how sinon compares with chai, jasmine, jest, and mocha, check out the comparison: Comparing chai vs jasmine vs jest vs mocha vs sinon.

Similar Npm Packages to testdouble

testdouble is a testing library designed for JavaScript applications that focuses on providing a simple and effective way to create test doubles, such as mocks, stubs, and spies. It aims to make testing more straightforward by allowing developers to easily replace dependencies in their tests, ensuring that they can isolate the code being tested. While testdouble is a powerful tool for creating test doubles, there are other libraries in the JavaScript ecosystem that offer similar functionalities. Here are a few alternatives:

  • jest is a widely-used testing framework developed by Facebook. It comes with built-in support for mocking and spying, making it a comprehensive solution for testing JavaScript applications. Jest provides a rich set of features, including snapshot testing, code coverage, and parallel test execution. Its user-friendly API and extensive documentation make it a popular choice among developers. If you're looking for an all-in-one testing solution that includes powerful mocking capabilities, Jest is an excellent option.
  • sinon is a standalone library that provides functions for creating spies, mocks, and stubs. It is often used in conjunction with other testing frameworks like Mocha or Jasmine. Sinon allows developers to create test doubles with fine-grained control, enabling them to simulate complex behaviors and verify interactions in their tests. If you prefer a library that focuses solely on test doubles and want to integrate it with your existing testing framework, Sinon is a great choice.

To see how testdouble compares with jest and sinon, check out the comparison: Comparing jest vs sinon vs testdouble.

README for jest-mock

jest-mock

Note: More details on user side API can be found in Jest documentation.

API

import {ModuleMocker} from 'jest-mock';

constructor(global)

Creates a new module mocker that generates mocks as if they were created in an environment with the given global object.

generateFromMetadata(metadata)

Generates a mock based on the given metadata (Metadata for the mock in the schema returned by the getMetadata() method of this module). Mocks treat functions specially, and all mock functions have additional members, described in the documentation for fn() in this module.

One important note: function prototypes are handled specially by this mocking framework. For functions with prototypes, when called as a constructor, the mock will install mocked function members on the instance. This allows different instances of the same constructor to have different values for its mocks member and its return values.

getMetadata(component)

Inspects the argument and returns its schema in the following recursive format:

{
  type: ...
  members: {}
}

Where type is one of array, object, function, or ref, and members is an optional dictionary where the keys are member names and the values are metadata objects. Function prototypes are defined by defining metadata for the member.prototype of the function. The type of a function prototype should always be object. For instance, a class might be defined like this:

const classDef = {
  type: 'function',
  members: {
    staticMethod: {type: 'function'},
    prototype: {
      type: 'object',
      members: {
        instanceMethod: {type: 'function'},
      },
    },
  },
};

Metadata may also contain references to other objects defined within the same metadata object. The metadata for the referent must be marked with refID key and an arbitrary value. The referrer must be marked with a ref key that has the same value as object with refID that it refers to. For instance, this metadata blob:

const refID = {
  type: 'object',
  refID: 1,
  members: {
    self: {ref: 1},
  },
};

Defines an object with a slot named self that refers back to the object.

fn(implementation?)

Generates a stand-alone function with members that help drive unit tests or confirm expectations. Specifically, functions returned by this method have the following members:

.mock

An object with three members, calls, instances and invocationCallOrder, which are all lists. The items in the calls list are the arguments with which the function was called. The "instances" list stores the value of 'this' for each call to the function. This is useful for retrieving instances from a constructor. The invocationCallOrder lists the order in which the mock was called in relation to all mock calls, starting at 1.

.mockReturnValueOnce(value)

Pushes the given value onto a FIFO queue of return values for the function.

.mockReturnValue(value)

Sets the default return value for the function.

.mockImplementationOnce(function)

Pushes the given mock implementation onto a FIFO queue of mock implementations for the function.

.mockImplementation(function)

Sets the default mock implementation for the function.

.mockReturnThis()

Syntactic sugar for:

mockFn.mockImplementation(function () {
  return this;
});

In case both .mockImplementationOnce() / .mockImplementation() and .mockReturnValueOnce() / .mockReturnValue() are called. The priority of which to use is based on what is the last call:

  • if the last call is .mockReturnValueOnce() or .mockReturnValue(), use the specific return value or default return value. If specific return values are used up or no default return value is set, fall back to try .mockImplementation();
  • if the last call is .mockImplementationOnce() or .mockImplementation(), run the specific implementation and return the result or run default implementation and return the result.
.withImplementation(function, callback)

Temporarily overrides the default mock implementation within the callback, then restores it's previous implementation.

If the callback is async or returns a thenable, withImplementation will return a promise. Awaiting the promise will await the callback and reset the implementation.

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