Isolated Test — Stripped-Down
How do you isolate-test a function when it has dependency(s) on it?
The gist of isolated test means we are not going to pass-in the real dependency. Like stunt doubles, we need a ‘double’ on the dependencies, namely test doubles.
- Mock. Mocking a dependency is merely to install a register on the dependency. A mocked dependency registers any calls to it: # of executions, and parameters.
- Stub. Stubbing a dependency is to return canned (hardcoded) results from the dependency.
These test doubles are designed for one sole purpose, to ensure our function interacts/contacts (act, react) correctly with the dependencies (without actually interact with it)
function (dependency) {
......
.........
......result = dependency(parameter1, parameter2, ....);....
.....return;
}
Illustrated in the stripped-down algorithms.
- We want to verify that function acted with correct parameters, executed the right amount (once, twice, thrice)
- We want to verify that function reacts correctly based on the canned results, i.e: by asserting on the state of the function.
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