Unit Tests in Swift Playground

UnitTests.swift

class Tests: XCTestCase {
    override func setUp() {
        super.setUp()
    }
    override func tearDown() {
        super.tearDown()
    }
}

class TestObserver: NSObject, XCTestObservation {

    func testCase(_ testCase: XCTestCase,
                  didFailWithDescription description: String,
                  inFile filePath: String?,
                  atLine lineNumber: Int) {
        assertionFailure(description, line: UInt(lineNumber))
    }
}

let testObserver = TestObserver()
XCTestObservationCenter.shared.addTestObserver(testObserver)

Tests.defaultTestSuite.run()