Integrate Combine Into an App
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Next episode: Part 2 Quiz: Integrate Combine into an App
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Testing is an important part of development for all apps. You can even write tests against your Combine code. You’ll use a pattern to organize your test logic - the Given-When-Then pattern.
func test_backgroundColorFor50TranslationPercentIsGreen() {
// Given
let viewModel = self.viewModel()
let translationPercent = 0.5
let expected = Color("Green")
var result: Color = .clear
After that, subscribe to the `$backgroundColor` publisher, using a `sink` to capture the value, and store the subscription.
viewModel.$backgroundColor
.sink(receiveValue: {
result = $0
})
.store(in: &subscriptions)
// When
viewModel.updateBackgroundColorForTranslation(translationPercent)
// Then
XCTAssert(result == expected, "Color expected to be \(expected) but was \(result)")
}
func test_fetchJokeSucceeds() {
// Given
let viewModel = self.viewModel()
let expectation = self.expectation(description: #function)
let expected = self.testJoke.value
var result: Joke!
viewModel.$joke
.dropFirst()
.sink(receiveValue: {
result = $0
expectation.fulfill()
})
.store(in: &subscriptions)
// When
viewModel.fetchJoke()
// Then
waitForExpectations(timeout: 1, handler: nil)
XCTAssert(result == expected, "Joke expected to be \(expected) but was \(String(describing: result))")
}