Testing assertion in Swift

Question

I\'m writing unit tests for a method that has an assertion. The Swift Language guide recommends using assertions for \"invalid conditions\":

Assertion

Answer 1

Agree with nschum's comment that it doesn't seem right to unit test assert because by default it wont be in the prod code. But if you really wanted to do it, here is the assert version for reference:

override assert

func assert(@autoclosure condition: () -> Bool, @autoclosure _ message: () -> String = "", file: StaticString = __FILE__, line: UInt = __LINE__) {
    assertClosure(condition(), message(), file, line)
}
var assertClosure: (Bool, String, StaticString, UInt) -> () = defaultAssertClosure
let defaultAssertClosure = {Swift.assert($0, $1, file: $2, line: $3)}

helper extension

extension XCTestCase {

    func expectAssertFail(expectedMessage: String, testcase: () -> Void) {
        // arrange
        var wasCalled = false
        var assertionCondition: Bool? = nil
        var assertionMessage: String? = nil
        assertClosure = { condition, message, _, _ in
            assertionCondition = condition
            assertionMessage = message
            wasCalled = true
        }

        // act
        testcase()

        // assert
        XCTAssertTrue(wasCalled, "assert() was never called")
        XCTAssertFalse(assertionCondition!, "Expected false to be passed to the assert")
        XCTAssertEqual(assertionMessage, expectedMessage)

        // clean up
        assertClosure = defaultAssertClosure
    }
}