This spec-code

var methodTest = sinon.stub();
methodTest('y');
methodTest.should.have.been.calledOnce
    .and.calledWith('y');

causes

✖ validates each validation
      Chrome 43.0.2357 (Mac OS X 10.9.5)
    TypeError: Cannot read property 'and' of undefined

with karma@0.13 version.

I've created simple project for bug repro:
https://github.com/AlexKVal/karma-test

master branch uses karma@0.13 and causes test fail
karma13 https://travis-ci.org/AlexKVal/karma-test/builds/71240835

https://github.com/AlexKVal/karma-test/tree/karma12 branch uses karma@0.12 version and works fine
karma12 https://travis-ci.org/AlexKVal/karma-test/builds/71240954