node-class-mock

Allows you to mock Class methods for use in testing with a few extra testy bits thrown in.

Example

This will replace the method on our TestClass prototype to a method which firstly checks the arguments passed to it and will assert.fail in the event of errors. It will then return a resolved Promise with the given output.

    // First, instantiate ClassMock with the class you would like to mock
    const classMock = new ClassMock( TestClass );

    // Then replace one of the methods
    const methodMock = classMock.mock( 'myMethod' )
        .shouldHaveArguments([
            { type: 'string', value: 'Hello, World!' },
            { value: 1 },
            { type: 'string', value: 'Sausages', optional: true }
        ])
        .resolves( 'Such Promise resolution!' )

    // Then anything which calls your mocked-method will
    // have it's inputs checked and receieve a resolved promise
    // ( other outcomes are available )
    const myTestClass = new TestClass();
    myTestClass.doStuff( 'Hello, World!', 1 ).then(
        out => console.log( 'Hey, my test works!' )
    );

    // Finally, remember to un-mock!
    methodMock.unMock();

To start-a-mocking, simply instantiate a ClassMock with your desired class ( non instantiated ). The ClassMock object exposes the following methods...

ClassMock

This can be considered the mock factory or the mock father or the mock-mack-daddy. Having instantiated it with your desired class, it will produce little method mock children.

• mock

  Main entry for overriding methods

  Arguments

  • methodName [Stirng] - Name of class method to override
  • callback [Function, Optional] - Function to use as mock
  • context [Object, Optional] - An instantiated object which acts as this in your override method

  Returns

  • methodMock [Object] - A representation of the mock dynamic

• unMock

  Reinstates original method

  Arguments

  • methodName [String] - Name of method to reinstate

• unMockAll

  Reinstate all mocked methods

Method Mocking

When calling mock on the mock-father you will receive back an object which exposes these methods...

• shouldHaveArguments

  Provide a list of expected arguments, assert.fail if any are amiss

  Arguments

  • argumentDescriptorList [Array|Object] - A list of objects describing each expected parameter

    • value - The expected value
    • type - The typeof the argument
    • optional - Some arguments are optional

• resolves

  The overriden method will result in a resolved Promise being returned with the given value.

  Arguments

  • output - Value to resolve

• rejects

  The overriden method will result in a rejected Promise being returned with the given error.

  Arguments

  • error - Value to reject

• returns

  The overriden method will result in the specified value being returned.

  Arguments

  • output - Value to reject

• throws

  The overriden method will result in the given error being thrown

  Arguments

  • error - Value to throw

• unMock

  Reinstate the original function

To develop

npm install
npm test

To compile

babel src/class-mock.js -o lib/class-mock.js

... to be continued