Testing and Debugging

Insert messages to see where you get, check values of key variables
- More advanced version of this: use debugging tool; set breakpoints
Apply “binary search” pattern: check status at mid-point of questionable code, then mid-point of appropriate half, etc.
Not sure what an error message means? You can often copy and paste it into your favorite search engine and get suggestions about what it might mean.
Null pointer exception: The most common cause of this error message is a method call on a null object, e.g.,
```
                obj.methodCall(param1, param2)
                
```
where obj is (unexpectedly) null.