Update NEWS.md

Author: 0xtch

NEWS.md

@@ -112,6 +112,8 @@
 
 10. `fwrite()` returns a clearer error message when `na = data.frame()` is used, [#7866](https://github.com/Rdatatable/data.table/issues/7866). Thanks @mcol for the report and the fix.
 
+11. `test()` now fails on unexpected console output, with the message `Test <num> produced unexpected output`, consistent with how unexpected warnings and messages are already handled, [#7847](https://github.com/Rdatatable/data.table/issues/7847). Thanks @MichaelChirico for the suggestion and @0xtch for the implementation.
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 ## data.table [v1.18.4](https://github.com/Rdatatable/data.table/milestone/45) (6 May 2026)
 
 ### BUG FIXES