how to ref. a value from another powershell script?

suppose i have 2 powershell scripts, t开发者_StackOverflow社区est1.ps1 and test2.ps1

#test1.ps1

$a="test1"

##################

#test2.ps1

echo $a

how to ref. $a in test2.ps1 from test1.ps1?

In Script 1:

Set-Variable -Name a -Value "test1" -Scope Global