43081j/hanbi

A small javascript library for stubbing and spying on methods/functions.

hanbi

hanbi is a rather small and simple library for stubbing and spying on methods and functions in JavaScript tests.

Install

$ npm i -D hanbi

Usage

spy()

Creates a single "spy" function to be used as input into some other function.

const spy = hanbi.spy();
window.addEventListener('load', spy.handler);
spy.called; // true once the event fires

stub(fn)

Creates a wrapped version of a given function which tracks any calls.

const fn = () => 5;
const stub = hanbi.stub(fn);
stub.handler(); // undefined
stub.called; // true

stubMethod(obj, method)

Replaces a given method on an object with a wrapped (stubbed) version of it.

class Foo {
  myMethod() {
    return 5;
  }
}
const instance = new Foo();
const stub = hanbi.stubMethod(instance, 'myMethod');
instance.myMethod(); // undefined
stub.called; // true

restore()

Restores all stubs/spies to their original functions.

class Foo {
  myMethod() {
    return 5;
  }
}
const instance = new Foo();
const stub = hanbi.stubMethod(instance, 'myMethod');
instance.myMethod(); // undefined
restore();
instance.myMethod(); // 5

Stub API

Each of the above mentioned entry points returns a Stub which has several useful methods.

class Stub {
  /**
   * Wrapped function
   */
  handler;

  /**
   * Function to be called when stub is restored
   */
  restoreCallback;

  /**
   * Original function
   */
  original;

  /**
   * Whether or not this stub has been called
   */
  called;

  /**
   * List of all calls this stub has received
   */
  calls;

  /**
   * Retrieves an individual call
   * @param index Index of the call to retrieve
   * @return Call at the specified index
   */
  getCall(index);

  /**
   * Retrieves the first call
   * @return Call object
   */
  firstCall;

  /**
   * Retrieves the last call
   * @return Call object
   */
  lastCall;

  /**
   * Number of times this stub has been called
   */
  callCount;

  /**
   * Specifies the value this stub should return
   * @param val Value to return
   */
  returns(val);

  /**
   * Specifies a function to call to retrieve the return value of this
   * stub
   * @param fn Function to call
   */
  callsFake(fn);

  /**
   * Enables pass-through, in that the original function is called when
   * this stub is called.
   */
  passThrough();

  /**
   * Resets call state (e.g. call count, calls, etc.)
   */
  reset();

  /**
   * Restores this stub.
   * This behaviour differs depending on what created the stub.
   */
  restore();

  /**
   * Asserts that the stub was called with a set of arguments
   * @param args Arguments to assert for
   * @return Whether they were passed or not
   */
  calledWith(...args);

  /**
   * Asserts that the stub returned a given value
   * @param val Value to check for
   * @return Whether the value was ever returned or not
   */
  returned(val);
}