Why I get error message printed on the console when running these two simple samples ?
I want that I get “Error testing :)” printed on the console insted of:

Get-WmiObject : The RPC server is
unavailable. (Exception from HRESULT:
0x800706BA) At line:3 char:15
+ Get-WmiObject <<<< -ComputerName possibly.nonexisting.domain.com
-Credential (Get-Credential) -Class Win32_logicaldisk
+ CategoryInfo : InvalidOperation: (:) [Get-WmiObject],
COMException
+ FullyQualifiedErrorId : GetWMICOMException,Microsoft.PowerShell.Commands.GetWmiObjectCommand

or

Attempted to divide by zero. At line:3
char:13
+ $i = 1/ <<<< 0
+ CategoryInfo : NotSpecified: (:) [],
ParentContainsErrorRecordException
+ FullyQualifiedErrorId : RuntimeException

First example:

Second example:

Thank you very much!

First example

The error happens at compile/parsing time (PowerShell is clever enough), so that the code is not even executed and it cannot catch anything, indeed. Try this code instead and you will catch an exception:

Second example

If you set $ErrorActionPreference = 'Stop' globally then you will get “Error testing :)” printed, as expected. But your $ErrorActionPreference is presumably 'Continue': in that case there is no terminating error/exception and you just get the non terminating error message printed to the host by the engine.

Instead of the global $ErrorActionPreference option you can also play with Get-WmiObject parameter ErrorAction. Try to set it to Stop and you will catch an exception.