Additional messages can be logged during a test case.
## Streaming macros
All these macros allow heterogenous sequences of values to be streaming using the insertion operator (```<<```) in the same way that std::ostream, std::cout, etc support it.
E.g.:
```c++
INFO( "The number is " <<i);
```
(Note that there is no initial ```<<``` - instead the insertion sequence is placed in parentheses.)
These macros come in three forms:
**INFO(** _message expression_**)**
The message is logged to a buffer, but only reported if a subsequent failure occurs within the same test case. This allows you to log contextual information in case of failures which is not shown during a successful test run. The buffer is cleared on the next successful assertion.
**SCOPED_INFO(** _message expression_**)**
As INFO, but is only in effect during the current scope. If a failure occurs beyond the end of the scope the message is not logged. In a looped block the message is reset on each iteration.
**WARN(** _message expression_**)**
The message is always reported.
**FAIL(** _message expression_**)**
The message is reported and the test case fails.
## Quickly capture a variable value
**CAPTURE(** _expression_**)**
Sometimes you just want to log the name and value of a variable. While you can easily do this with the INFO macro, above, as a convenience the CAPTURE macro handles the stringising of the variable name for you (actually it works with any expression, not just variables).
