BLACK FRIDAY SALE: Save big on all my Swift books and bundles! >>

How to check and unwrap optionals in tests using XCTUnwrap()

Swift version: 5.6

Paul Hudson    @twostraws   

When writing tests, it’s common to want to unwrap an optional before checking it for a particular value. XCTUnwrap() does exactly that for us: it attempts to unwrap the optional, but will throw an error (and thus fail the test) if the optional is nil.

For example, if you have a User struct with a getAuthenticationToken() method that returns an optional string, you can use XCTUnwrap() like this:

func testTokenGenerationSucceeds() throws {
    let user = User()
    let token = try XCTUnwrap(user.getAuthenticationToken())
    XCTAssertEqual(token.count, 40)
}

That test is marked with throws, which allows us to call XCTUnwrap() and propagate any errors if it finds our optional is empty.

This approach is cleaner than what we might have written previously:

func testTokenGenerationSucceeds2() {
    let user = User()
    if let token = user.getAuthenticationToken() {
        XCTAssertEqual(token.count, 40)
    } else {
        XCTFail("Failed to generate valid token.")
    }
}

It’s worth adding that in trivial cases such as this one, it’s possible to compare optionals with non-optionals in less code, like this:

func testTokenGenerationSucceeds3() throws {
    let user = User()
    XCTAssertEqual(user.getAuthenticationToken()?.count, 40)
}

However, things aren’t so straightforward when you need to work with optional chaining in a longer test – that’s really where XCTUnwrap() will come into its own.

Hacking with Swift is sponsored by RevenueCat

SPONSORED In-app subscriptions are a pain to implement, hard to test, and full of edge cases. RevenueCat makes it straightforward and reliable so you can get back to building your app. Oh, and it's free if your app makes less than $10k/mo.

Learn more

Sponsor Hacking with Swift and reach the world's largest Swift community!

Available from iOS 13.0

Similar solutions…

About the Swift Knowledge Base

This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.

BUY OUR BOOKS
Buy Pro Swift Buy Pro SwiftUI Buy Swift Design Patterns Buy Testing Swift Buy Hacking with iOS Buy Swift Coding Challenges Buy Swift on Sundays Volume One Buy Server-Side Swift Buy Advanced iOS Volume One Buy Advanced iOS Volume Two Buy Advanced iOS Volume Three Buy Hacking with watchOS Buy Hacking with tvOS Buy Hacking with macOS Buy Dive Into SpriteKit Buy Swift in Sixty Seconds Buy Objective-C for Swift Developers Buy Beyond Code

Was this page useful? Let us know!

Average rating: 4.5/5

 
Unknown user

You are not logged in

Log in or create account
 

Link copied to your pasteboard.