This is a major release which introduces many new featues, such as sandboxes, as well as new convenience methods and assertions.

This major release also comes with some breaking changes:

Breaking Changes

• removed reset method. #35 (@stalniy)
  You will need to update any callsites to spy.reset() to instead assign a new spy to that variable or property.

• exposes original function body in spy.toString calls #93 (@stalniy)
  If you check the spy.toString() output in your tests, this will need to be changed to accomodate for this change.

Features

• added spy.returns #35 (@stalniy)
  Allows to create spies that return constant value

• added spy.on #61 (#38, @stalniy)
  Allows to add spies on existing methods

• added posibility to replace original method when spying with spy.on #68 (#62, @stalniy)

chai.spy.on(array, 'push', returns => 5)
chai.spy.on(array, 'push', function() {
  // custom implementation
})

• added spy.restore #61 (#38, @stalniy)
  Allows to remove spies added by spy.on and restore original method implementation

• added support for sanboxes #61 (#38, @stalniy)
  Now it's possible to create sanboxes and track/restore spies in sandbox

• added support for nth call checks #75 (#59, @cnexans)
  Allows to check spy arguments on specified call

const spy = chai.spy()

spy(1); // first call
spy(2); // second call
spy(3); // third call
spy(i); // nth call

expect(spy).to.have.been.first.called.with(1)
expect(spy).to.have.been.second.called.with(2)
expect(spy).to.have.been.third.called.with(3)
expect(spy).on.nth(i).be.called.with(i)

Bug Fixes

• removed dead links in README #84, #80 (#79, @damianb)
• fixed formatting in README #67 (@jethrolarson)
• added MIT license to package.json #58 (@reiz)
• fixed .with when multiple identical arguments are passed in spy call #56 (#45, @meeber)
• updated reference to github repository #42 (@robcolburn)

Documentation

• better organization for spy methods #92 (@stalniy)
• added documentation about sanboxes #92 (@stalniy)