Open Radar

 
Summary:
Swift tests do not have access to the XCTAssertThrows family of macros. In addition, Swift does not provide a try-catch mechanism. This makes testing any code that raises a runtime exception impossible.

Steps to Reproduce:
1. Define a function that asserts a user is logged in:

func assertUserIsLoggedIn(isLoggedIn: Bool) {
	if(!isLoggedIn) {
		NSException.raise(NSInternalInconsistencyException,
			format: "Programmer error. This function should only be called after authentication.",
			arguments: CVaListPointer(fromUnsafePointer: UnsafePointer()))
	}
}

2. Attempt to write a unit test that confirms that the function behaves as expected. That is, the test should pass if the function raises when given a false value as a parameter.

Expected Results:
Expected (1):

Using XCTAssertThrows, I am able to test the function:

XCTAssertThrows(assertUserIsLoggedIn(false), "expected function to raise")

Expected (2):

Using try-catch, I am able to test the function:

var raised = false
@try {
    assertUserIsLoggedIn(false)
} @catch {
    raised = true
}
XCTAssertTrue(raised, "excpected function to raise")

Actual Results:
There is no way to test the function. The following test will fail:

class UserAssertionTests: XCTestCase {
    func testAssertUserIsLoggedInRaisesWhenNotLoggedIn() {
		assertUserIsLoggedIn(false) // Exception causes test failure.
    }
}

Version:
Xcode Version 6.0 (6A215l), OS X 10.10 (14A238x)

Notes:
In WWDC 2013, Apple developers appeared to be enthusiastic about improving unit testing and continuous integration in Xcode. But without a way to test runtime errors, developers writing in Swift are severely limited in how they can test their applications.

Related thread on the Apple Developer Forums: https://devforums.apple.com/message/970961

Configuration:
This problem does not exist when writing tests in Objective-C.