When using sinon I just want to replace my function's return value and don't need other infos like how many time it was called. Which one of them is better?

sinon.replace(Component.prototype, 'getValue', () => 123);

const myStub = sinon.stub(Component.prototype, 'getValue');
myStub.return(123);

When using sinon I just want to replace my function's return value and don't need other infos like how many time it was called. Which one of them is better?

sinon.replace(Component.prototype, 'getValue', () => 123);

const myStub = sinon.stub(Component.prototype, 'getValue');
myStub.return(123);

• javascript
• sinon

1 Answer 1

I rarely see sinon.replace being used in many projects. The advantage of using stub is you can modify the return value many times for example.

let getValueStub;

before(function() {
   getValueStub = sinon.stub(Component.prototype, 'getValue');
})

after(function() {
   sinon.restore();
})

it('test case A if return value is 123', function() {
   getValueStub.returns(123);
   // do expectation
})

it('test case B if return value is 234', function() {
   getValueStub.returns(234);
   // do expectation
})

Meanwhile, for replace, based on Sinon documentation, you can use it only one time.

sandbox.replace(object, property, replacement);

Replaces property on object with replacement argument. Attempts to replace an already replaced value cause an exception.

replacement can be any value, including spies, stubs and fakes.

For example:

sinon.replace(Component.prototype, 'getValue', function () {
  return 123;
});

sinon.replace(Component.prototype, 'getValue', function () { // this will return error
  return 456;
});

it will return error

TypeError: Attempted to replace getValue which is already replaced

You probably can achieve the same thing like stub with sinon.replace by replacing the function with stub

getValueStub = sinon.stub();    
sinon.replace(Component.prototype, 'getValue', getValueStub);

getValueStub.returns(123); 
getValueStub.returns(456);

Still, I prefer use sinon.stub due to simplicity.

Reference:

https://sinonjs/releases/v7.2.2/sandbox/#sandboxreplaceobject-property-replacement