     }
 
     func testGliderRegistrationHeader() {
-        let header = IGCHeaderField.parseHLine(hLine: gliderRegistrationString)
+        guard let header = IGCHeaderField.parseHLine(hLine: gliderRegistrationString) else { XCTFail("expecting a reg header but got nil"); return }
         switch header {
         case .gliderRegistration(let registration):
             print("glider registration \(registration)")

    }

    func testAccuracyHeader() {
        let accuracyHeader = IGCHeaderField.parseHLine(hLine: accuracyHeaderString)
        switch accuracyHeader {
        case .accuracy(let acc):
            print("accuracy \(acc)")

    // MARK: - Tests for line parsing

    func testDateHeader() {
        guard let dateHeader = IGCHeaderField.parseHLine(hLine: dateHeaderString) else { XCTFail("expecting a date header but got nil"); return }
        switch dateHeader {
        case .date(let d):
            print("date \(d)")
