Specifying Test Double Behavior

Once we have a testdouble.js function, we need to specify some behavior, analogous to how RSpec’s test doubles use allow and expect with chained methods like to_receive.

Adding behavior

In testdouble.js, we add behavior with the when method, and the API to it is a little unusual. Here’s a basic usage:

const fake = td.object["remoteInit"]
td.when(fake.remoteInit(1)).thenReturn(7)

There are two parts to this when invocation:

• The call to when itself.
• The chained method afterward that defines the behavior.

The argument to when is meant to be the entire ...