     appendedSequence = [Int]().asSequence().append(sequence1)
     XCTAssertTrue(appendedSequence.asArray().count == sequence1.asArray().count)
     
+    appendedSequence = [Int]().asSequence().append([Int]().asSequence())
+    XCTAssertTrue(appendedSequence.asArray().count == 0)
+    
   }
   
   

    
    sequence1 = numbers.asSequence().delete(12)
    XCTAssertTrue(sequence1.asArray().count == numbers.count)
    
    XCTAssertTrue(empty.asSequence().delete("").asArray().count == 0)
    
  }

    
    let numbers = [4, 2, 5, 6, 1, 2, 3]
    
    XCTAssertTrue(numbers.asSequence().dropwhile( { $0 <= 5 } ).asArray().count == 4)
    
    XCTAssertTrue(numbers.asSequence().dropwhile( { $0 <= 3 } ).asArray().count == numbers.count)
    
    XCTAssertTrue(empty.asSequence().dropwhile( {$0 == "A"} ).asArray().count == 0)
    
  }
  
