MtuTestCallback

```
public interface MtuTestCallback
```
Callback used to test out an MTU size adjustment. Some phones (OnePlus 2, Moto Pure X are 2 we know of for sure) will report a success on getting a larger MTU, but fail when trying to write with the requested MTU size. This callback exists to test the MTU before saying things are fine. Once the MTU request comes back as a success, this callback will be invoked to see if a test should be performed. The onResult(TestResult) method will be called if it either fails, or succeeds. If the write fails, the device will be disconnected, as once a bluetooth operation times out in this manner, nothing else will work until the device gets re-connected.

Nested Classes
Modifier and Type	Interface and Description
`static class`	`MtuTestCallback.MtuTestEvent` Class passed in to `onTestRequest(MtuTestEvent)` when an MTU has been successfully negotiated to see if SweetBlue should now test it to make sure it works as it's supposed to.
`static class`	`MtuTestCallback.Please` Please class used to tell SweetBlue if it should test the new MTU size, and if so, which service uuid, and char uuid to use, and the data to write (the data should be the size of the MTU size requested to properly test).
`static class`	`MtuTestCallback.TestResult` Enumeration reporting the result of an MTU test.

All Methods Instance Methods Abstract Methods
Modifier and Type	Method and Description
`void`	`onResult(MtuTestCallback.TestResult result)` This gets called if the MTU test succeeds, or fails.
`MtuTestCallback.Please`	`onTestRequest(MtuTestCallback.MtuTestEvent event)` This gets called after `BleDevice.negotiateMtu(int, ReadWriteListener)` or any of it's overloads is called, and it returns a success.

Interface MtuTestCallback