Verifying function call and inspecting arguments using sinon spies

Question

In your case, you are trying to see if bar was called, so you want to spy bar rather than foo.

As described in the doc :

function bar(x,y) {
  console.debug(x, y);
}
function foo(z) {
  bar(z, z+1);
}
// Spy on the function "bar" of the global object.
var spy = sinon.spy(window, "bar");

// Now, the "bar" function has been replaced by a "Spy" object
// (so this is not necessarily what you want to do) 

foo(1);

bar.getCall(0).args => should be [1,2]

Now, spying on the internals of the function strongly couples your test of “foo” to its implementation, so you’ll fall into the usual “mockist vs classical” debate.

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