Why does Travis fail despite all unit tests succeeding?

Trying to set up continuous integration for what is basically an empty and fresh swift project in Xcode 7 (code below). In the travis log I can see that all (two) unit tests succeeded. Travis outputs the error in the screenshot below. Any ideas?

Noteworthy:

1. Scheme has been set to 'Shared'.
2. All two Unit Tests succeed.

Screenshot of Travis-CI log output

Contents of .travis.yml

language: objective-c
osx_image: xcode7
xcode_project: Toys.xcodeproj
xcode_scheme: Toys
xcode_sdk: iphonesimulator9.0

Contents of Toy.swift (the only modified file in the main target)

import Foundation

class Toy {

    func isToy() -> Bool {
        return true
    }

    func isExpensive() -> Bool {
        return true
    }
}

Contents of ToysTests.swift

import XCTest

@testable import Toys

class ToysTests: XCTestCase {

    override func setUp() {
        super.setUp()
    }

    override func tearDown() {
        super.tearDown()
    }

    func testIsToy() {

        if let myToy: Toy? = Toy() {

            XCTAssertTrue(myToy!.isToy())

        }
    }

    func testIsExpensive() {

        if let myToy: Toy? = Toy() {
            XCTAssertTrue(myToy!.isExpensive())
        }
    }
}