function dummy {
    return Get-Date -f "dd"
}

$here = Split-Path -Parent $MyInvocation.MyCommand.Path
$sut = (Split-Path -Leaf $MyInvocation.MyCommand.Path) -replace '.Tests.', '.'
. "$here$sut"

Describe "dummy" {
    Mock Get-Date { return "01" } -Verifiable -ParameterFilter {$f -match "dd"}

    It "does something useful" {
        dummy

        Assert-VerifiableMocks
    }
}

Describing dummy
 [-] does something useful 99ms
   RuntimeException:  Expected Get-Date to be called with $f -match "dd"
   at Assert-VerifiableMocks, C:Program FilesWindowsPowerShellModulesPester3.4.0FunctionsMock.ps1: line 434
   at <ScriptBlock>, E:…dummy.Tests.ps1: line 11
Tests completed in 99ms
Passed: 0 Failed: 1 Skipped: 0 Pending: 0 Inconclusive: 0

Name                           Value
----                           -----
PSVersion                      5.1.14393.1198
PSEdition                      Desktop
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0...}
BuildVersion                   10.0.14393.1198
CLRVersion                     4.0.30319.42000
WSManStackVersion              3.0
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1

Mock Get-Date { return "01" } -Verifiable -ParameterFilter {$format -match "dd"}

Describing dummy
 [+] does something useful 31ms