 
 extension ObservableBlockingTest {
     func testFirst_empty() {
-        XCTAssertNil(try! Observable<Int>.empty().toBlocking().first())
+        XCTAssertNil(try Observable<Int>.empty().toBlocking().first())
     }
     
     func testFirst_return() {
-        XCTAssertEqual(try! Observable.just(42).toBlocking().first(), 42)
+        XCTAssertEqual(try Observable.just(42).toBlocking().first(), 42)
     }
     
     func testFirst_fail() {


extension ObservableBlockingTest {
    func testLast_empty() {
        XCTAssertNil(try! Observable<Int>.empty().toBlocking().last())
    }
    
    func testLast_return() {
        XCTAssertEqual(try! Observable.just(42).toBlocking().last(), 42)
    }
    
    func testLast_fail() {

    }
    
    func testFirst_someData() {
        XCTAssertEqual(try Observable.of(42, 43, 44, 45).toBlocking().first(), 42)
    }
    
    func testFirst_withRealScheduler() {
