Rich Javascript Assertions Part 2: Sinon

A quick description of the assertions provided by Sinon

Transcript

1. Rich Javascript Assertions Part 2: Sinon Daniel Brook-Roberge Engineering Meeting
2. Rich Assertions • Javascript testing libraries provide a wide variety of test assertions. • Beyond the “basic” assertions of truth, falseness, equality, and type, we have “rich” assertions which assert something more specific. • Rich assertions allow both clearer code and more explanatory error messages on failure. • This talk describes rich assertions in Sinon.
3. Sinon • Sinon is a function mocking library for Javascript. • It can stub out or spy upon functions, and then allows access to the call count, arguments, return values, etc. • The Sinon rich assertions can be included in the Chai assert object by doing: sinon.assert.expose(chai.assert, { prefix: "" });
4. assert.calledOnce • assert.isTrue(stub.calledOnce); becomes assert.calledOnce(stub); • On failure, this prints the name of the stub and the actual call count. • There are also calledTwice and calledThrice assertions.
5. assert.notCalled • assert.isFalse(spy.called); becomes assert.notCalled(spy); • On failure, it shows the name of the stub and the actual call count, just as with calledOnce.
6. assert.calledWith • assert.isTrue(stub.calledWith(arg1,...)); assert.equal(stub.args[0][0], arg1); become assert.calledWith(stub, arg1...); • On failure, it shows the stub name and intended arguments • This assertion allows incomplete matching of argument lists.
7. assert.calledWithExactly • assert.isTrue(spy.calledWithExactly(arg1,...)); assert.deepEqual(spy.args[0], [arg1,...]); become assert.calledWithExactly(spy, arg1,...); • Unlike calledWith, calledWithExactly must include all the function’s arguments to pass.
8. assert.callOrder • assert.callOrder(stub1, stub2,...); passes if and only if the stubs are called in the specified order. • I don’t actually know how to do this without the rich assertion.