         var data = a.withUnsafeBufferPointer {
             return Data(buffer: $0)
         }
-        let expectedSize = strideof(UInt8.self) * a.count
+        let expectedSize = MemoryLayout<UInt8>.stride * a.count
         expectEqual(expectedSize, data.count)
         
         let underlyingBuffer = unsafeBitCast(malloc(expectedSize - 1)!, to: UnsafeMutablePointer<UInt8>.self)

            return Data(buffer: $0)
        }
        
        var expectedSize = strideof(Int32.self) * a.count
        expectEqual(expectedSize, data.count)
        
        [false, true].withUnsafeBufferPointer {
            data.append($0)
        }
        
        expectedSize += strideof(Bool.self) * 2
        expectEqual(expectedSize, data.count)
        
        let underlyingBuffer = unsafeBitCast(malloc(expectedSize)!, to: UnsafeMutablePointer<UInt8>.self)

            return Data(buffer: $0)
        }
        
        expectEqual(data.count, MemoryLayout<MyStruct>.stride * 3)
        
        
        // append
