Unit test a ViewModel with a mocked NetworkService
WHAT IT TESTS: dependency injection and test isolation. OUTLINE: inject the protocol, supply a mock returning canned data, assert published state transitions. RED FLAG: hitting the real network or testing the concrete service instead of the ViewModel.
WHAT IT TESTS: whether you isolate units via protocol-based dependency injection. ANSWER OUTLINE: the ViewModel takes NetworkService as an init parameter; in the test you pass a MockNetworkService conforming to that protocol that returns a stubbed success result; you trigger the fetch and assert the ViewModel's published or observable state moves from loading to loaded with the expected model. RED FLAG: making a real URLSession call, depending on live servers, or asserting on the mock rather than the ViewModel's resulting state.
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- #ios
- #swift
- #unit-testing
- #dependency-injection
- #mocking
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