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Expectations.md

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Expectations and confirmations

Check for expected values, outcomes, and asynchronous events in tests.

Overview

Use expect(_:_:sourceLocation:) and require(_:_:sourceLocation:)-5l63q macros to validate expected outcomes. To validate that an error is thrown, or not thrown, the testing library provides several overloads of the macros that you can use. For more information, see doc:testing-for-errors-in-swift-code.

Use a Confirmation to confirm the occurrence of an asynchronous event that you can't check directly using an expectation. For more information, see doc:testing-asynchronous-code.

Validate your code's result

To validate that your code produces an expected value, use expect(_:_:sourceLocation:). This macro captures the expression you pass, and provides detailed information when the code doesn't satisfy the expectation.

@Test func calculatingOrderTotal() {
  let calculator = OrderCalculator()
  #expect(calculator.total(of: [3, 3]) == 7)
  // Prints "Expectation failed: calculator.total(of: [3, 3]) == 7"
}

Your test keeps running after expect(_:_:sourceLocation:) fails. To stop the test when the code doesn't satisfy a requirement, use require(_:_:sourceLocation:)-5l63q instead:

@Test func returningCustomerRemembersUsualOrder() throws {
  let customer = try #require(Customer(id: 123))
  // The test runner doesn't reach this line if the customer is nil.
  #expect(customer.usualOrder.countOfItems == 2)
}

require(_:_:sourceLocation:)-5l63q throws an instance of ExpectationFailedError when your code fails to satisfy the requirement.

Topics

Checking expectations

  • expect(_:_:sourceLocation:)
  • require(_:_:sourceLocation:)-5l63q
  • require(_:_:sourceLocation:)-6w9oo

Checking that errors are thrown

  • doc:testing-for-errors-in-swift-code
  • expect(throws:_:sourceLocation:performing:)-1hfms
  • expect(throws:_:sourceLocation:performing:)-7du1h
  • expect(_:sourceLocation:performing:throws:)
  • require(throws:_:sourceLocation:performing:)-7n34r
  • require(throws:_:sourceLocation:performing:)-4djuw
  • require(_:sourceLocation:performing:throws:)

Checking how processes exit

  • doc:exit-testing
  • expect(processExitsWith:observing:_:sourceLocation:performing:)
  • require(processExitsWith:observing:_:sourceLocation:performing:)
  • ExitStatus
  • ExitTest

Confirming that asynchronous events occur

  • doc:testing-asynchronous-code
  • confirmation(_:expectedCount:isolation:sourceLocation:_:)-5mqz2
  • confirmation(_:expectedCount:isolation:sourceLocation:_:)-l3il
  • Confirmation

Retrieving information about checked expectations

  • Expectation
  • ExpectationFailedError

Representing source locations

  • SourceLocation