I think this message should clarify that private methods are not accessible in expectations. It might seem obvious to some, but it reads (to me) like "I was trying to make a left turn, but I was thirsty" (the "but" being somewhat orthogonal to the expectation).

In normal use, calling privates from the outside results in an error e.g. 

```
NoMethodError: private method `print' called for "this":String
```

Why not treat these as errors as well, e.g. 

```
NoMethodError: private method `print' called for "this":String (expectations on private methods are not supported)
```

Or even take it a step further:

```
UnsupportedOperationError: expectation set on private method `print' for "this":String
```