Add the Powers of spying to JavaScript tests
npm install --save-dev austin
var austin = require('austin');
var testSubject = {
testFunction: function () {
return 5;
},
anotherFunction: function () {
return 'hello';
}
};
// Inform Austin of the method to spy on...
austin.spy(testSubject, 'testFunction');
// Austin adds spy utilities...
testSubject.testFunction.callCount();
// => 0
// Austin allows executing the function...
testSubject.testFunction('green', 3, {x: ['seven']});
// => 5
// Austin tracks the number of times the spied function was called...
testSubject.testFunction.callCount();
// => 1
// And the parameters passed to each call of the spied function
testSubject.testFunction.calls[0];
// => ['green', 3, {x: ['seven']}]
// And knows if a Spied Function was called with params...
testSubject.testFunction.calledWith('green', 3, {x: ['seven']});
// => true
testSubject.testFunction.calledWith('blue');
// => false
// And can intercept the return value of the Spied Function
testSubject.test.returns('a fake value');
testSubject.test();
// => 'a fake value'
testSubject.test.throws(TypeError, 'Expected value to be a string');
testSubject.test();
// => TypeError: Expected value to be a string
// And can intercept the return value of the Spied Function with specific parameters
testSubject.test.withArgs('austin').returns('powers');
testSubject.test('austin');
// => 'powers'
testSubject.test.withArgs('austin').callCount();
// => 1
// And supports chaining withArgs and returns
testSubject.test.returns('Groovy!')
.withArgs('austin').returns('powers')
.withArgs('oooo').returns('behave');
testSubject.test();
// => 'Groovy!'
testSubject.test('austin');
// => 'powers'
testSubject.test('oooo');
// => 'behave'
testSubject.test('Dr. Evil');
// => 'Groovy!'
// And can chain initial spy call
austin.spy(testSubject, 'anotherFunction').returns('bye')
.withArgs('live').returns('dangerously');
testSubject.anotherFunction();
// => 'bye'
testSubject.anotherFunction('live');
// => 'dangerously'
// Austin can reset spy analytics and fake value returns...
testSubject.testFunction.withArgs('Dr.').returns('Evil');
testSubject.testFunction.reset();
testSubject.testFunction.callCount();
// => 0
testSubject.testFunction.calls;
// => []
testSubject.testFunction('Dr.');
// => 5
// When Austin is told to halt spying...
testSubject.testFunction.restore();
// Spy utilities are removed...
testSubject.testFunction.callCount;
// => undefined
// And the function returns to its former self.
testSubject.testFunction();
// => 5
// And Austin is smart enough to make new spies...
var nigelPowers = austin.spy();
nigelPowers.returns('Judo Chop');
nigelPowers();
// => 'Judo Chop'Creates a new Spied Function.
Adds spy related utilities to obj[methodName] by transforming the function to a Spied Function.
Note: returns Spied Function for easy chaining with returns and withArgs.
Type: Object
An object that has the desired method methodName to be spied on.
Type: *
Can be any type as long as obj[methodName] is a function.
A Spied Function has additional properties and methods to aid testing
Executes the original function, while updating spy analytics such as call count.
The number of times spiedFunction was executed.
Returns a Boolean if spiedFunction was called with params.
Type: ...*
Params is a list of any types.
An array of parameters passed to each execution of Spied Function.
Resets spiedFunction.callCount() to 0, spiedFunction.calls to [], and resets any fake values set with returns.
Restores the spiedFunction to its original function and removes all spy utilities.
When spiedFunction is called, it will return value instead of executing the original function.
Note: returns spiedFunction for easy chaining with withArgs.
Note: if calling spiedFunction.withArgs(...).returns(...) with params that already have a fake value, then the
new value passed to returns will override the previous value.
Type: *
Any value that is desired to be returned by spiedFunction().
When spiedFunction is called, it will throw an error instance of errorType with an optional message message.
Note: returns spiedFunction for easy chaining with withArgs.
Note: spiedFunction.throws has priority over spiedFunction.returns regardless of order called.
Type: Error
An instance of Error to be thrown.
Type: String
An optional message to throw error with.
Returns an object with a returns method to fake return values of calls to spiedFunction with params and callCount and a throws to throw errors when spiedFunction is called with params.
Note: spiedFunction.withArgs(...).returns(...) and spiedFunction.withArgs(...).throws(...) return spiedFunction for easy chaining like spiedFunction.withArgs(...).returns(...).withArgs(...).returns(...).
Type: ...*
An array of any types
MIT © Dustin Specker