Windows PowerShell command on Get-command Mock

NAME
    Mock
    
SYNOPSIS
    Mocks the behavior of an existing command with an alternate
    implementation.
    
    
SYNTAX
    Mock [[-CommandName] ] [[-MockWith] ] [-Verifiable] [[-ParameterFilter] ] 
    [[-ModuleName] ] []
    
    
DESCRIPTION
    This creates new behavior for any existing command within the scope of a
    Describe or Context block. The function allows you to specify a script block
    that will become the command's new behavior.
    
    Optionally, you may create a Parameter Filter which will examine the
    parameters passed to the mocked command and will invoke the mocked
    behavior only if the values of the parameter values pass the filter. If
    they do not, the original command implementation will be invoked instead
    of a mock.
    
    You may create multiple mocks for the same command, each using a different
    ParameterFilter. ParameterFilters will be evaluated in reverse order of
    their creation. The last one created will be the first to be evaluated.
    The mock of the first filter to pass will be used. The exception to this
    rule are Mocks with no filters. They will always be evaluated last since
    they will act as a "catch all" mock.
    
    Mocks can be marked Verifiable. If so, the Assert-VerifiableMocks command
    can be used to check if all Verifiable mocks were actually called. If any
    verifiable mock is not called, Assert-VerifiableMocks will throw an
    exception and indicate all mocks not called.
    
    If you wish to mock commands that are called from inside a script module,
    you can do so by using the -ModuleName parameter to the Mock command. This
    injects the mock into the specified module. If you do not specify a
    module name, the mock will be created in the same scope as the test script.
    You may mock the same command multiple times, in different scopes, as needed.
    Each module's mock maintains a separate call history and verified status.
    

PARAMETERS
    -CommandName 
        The name of the command to be mocked.
        
        Required?                    false
        Position?                    1
        Default value                
        Accept pipeline input?       false
        Accept wildcard characters?  false
        
    -MockWith 
        A ScriptBlock specifying the behvior that will be used to mock CommandName.
        The default is an empty ScriptBlock.
        NOTE: Do not specify param or dynamicparam blocks in this script block.
        These will be injected automatically based on the signature of the command
        being mocked, and the MockWith script block can contain references to the
        mocked commands parameter variables.
        
        Required?                    false
        Position?                    2
        Default value                {}
        Accept pipeline input?       false
        Accept wildcard characters?  false
        
    -Verifiable []
        When this is set, the mock will be checked when Assert-VerifiableMocks is
        called.
        
        Required?                    false
        Position?                    named
        Default value                False
        Accept pipeline input?       false
        Accept wildcard characters?  false
        
    -ParameterFilter 
        An optional filter to limit mocking behavior only to usages of
        CommandName where the values of the parameters passed to the command
        pass the filter.
        
        This ScriptBlock must return a boolean value. See examples for usage.
        
        Required?                    false
        Position?                    3
        Default value                {$True}
        Accept pipeline input?       false
        Accept wildcard characters?  false
        
    -ModuleName 
        Optional string specifying the name of the module where this command
        is to be mocked.  This should be a module that _calls_ the mocked
        command; it doesn't necessarily have to be the same module which
        originally implemented the command.
        
        Required?                    false
        Position?                    4
        Default value                
        Accept pipeline input?       false
        Accept wildcard characters?  false
        
    
        This cmdlet supports the common parameters: Verbose, Debug,
        ErrorAction, ErrorVariable, WarningAction, WarningVariable,
        OutBuffer, PipelineVariable, and OutVariable. For more information, see 
        about_CommonParameters (https:/go.microsoft.com/fwlink/?LinkID=113216). 
    
INPUTS
    
OUTPUTS
    
    -------------------------- EXAMPLE 1 --------------------------
    
    PS C:\>Mock Get-ChildItem { return @{FullName = "A_File.TXT"} }
    
    Using this Mock, all calls to Get-ChildItem will return a hashtable with a
    FullName property returning "A_File.TXT"
    
    
    
    
    -------------------------- EXAMPLE 2 --------------------------
    
    PS C:\>Mock Get-ChildItem { return @{FullName = "A_File.TXT"} } -ParameterFilter { $Path -and 
    $Path.StartsWith($env:temp) }
    
    This Mock will only be applied to Get-ChildItem calls within the user's temp directory.
    
    
    
    
    -------------------------- EXAMPLE 3 --------------------------
    
    PS C:\>Mock Set-Content {} -Verifiable -ParameterFilter { $Path -eq "some_path" -and $Value -eq "Expected Value" }
    
    When this mock is used, if the Mock is never invoked and Assert-VerifiableMocks is called, an exception will be 
    thrown. The command behavior will do nothing since the ScriptBlock is empty.
    
    
    
    
    -------------------------- EXAMPLE 4 --------------------------
    
    PS C:\>Mock Get-ChildItem { return @{FullName = "A_File.TXT"} } -ParameterFilter { $Path -and 
    $Path.StartsWith($env:temp\1) }
    
    Mock Get-ChildItem { return @{FullName = "B_File.TXT"} } -ParameterFilter { $Path -and 
    $Path.StartsWith($env:temp\2) }
    Mock Get-ChildItem { return @{FullName = "C_File.TXT"} } -ParameterFilter { $Path -and 
    $Path.StartsWith($env:temp\3) }
    
    Multiple mocks of the same command may be used. The parameter filter determines which is invoked. Here, if 
    Get-ChildItem is called on the "2" directory of the temp folder, then B_File.txt will be returned.
    
    
    
    
    -------------------------- EXAMPLE 5 --------------------------
    
    PS C:\>Mock Get-ChildItem { return @{FullName="B_File.TXT"} } -ParameterFilter { $Path -eq "$env:temp\me" }
    
    Mock Get-ChildItem { return @{FullName="A_File.TXT"} } -ParameterFilter { $Path -and $Path.StartsWith($env:temp) }
    
    Get-ChildItem $env:temp\me
    
    Here, both mocks could apply since both filters will pass. A_File.TXT will be returned because it was the most 
    recent Mock created.
    
    
    
    
    -------------------------- EXAMPLE 6 --------------------------
    
    PS C:\>Mock Get-ChildItem { return @{FullName = "B_File.TXT"} } -ParameterFilter { $Path -eq "$env:temp\me" }
    
    Mock Get-ChildItem { return @{FullName = "A_File.TXT"} }
    
    Get-ChildItem c:\windows
    
    Here, A_File.TXT will be returned. Since no filter was specified, it will apply to any call to Get-ChildItem that 
    does not pass another filter.
    
    
    
    
    -------------------------- EXAMPLE 7 --------------------------
    
    PS C:\>Mock Get-ChildItem { return @{FullName = "B_File.TXT"} } -ParameterFilter { $Path -eq "$env:temp\me" }
    
    Mock Get-ChildItem { return @{FullName = "A_File.TXT"} }
    
    Get-ChildItem $env:temp\me
    
    Here, B_File.TXT will be returned. Even though the filterless mock was created more recently. This illustrates 
    that filterless Mocks are always evaluated last regardlss of their creation order.
    
    
    
    
    -------------------------- EXAMPLE 8 --------------------------
    
    PS C:\>Mock Get-ChildItem { return @{FullName = "A_File.TXT"} } -ModuleName MyTestModule
    
    Using this Mock, all calls to Get-ChildItem from within the MyTestModule module
    will return a hashtable with a FullName property returning "A_File.TXT"
    
    
    
    
    -------------------------- EXAMPLE 9 --------------------------
    
    PS C:\>Get-Module -Name ModuleMockExample | Remove-Module
    
    New-Module -Name ModuleMockExample  -ScriptBlock {
        function Hidden { "Internal Module Function" }
        function Exported { Hidden }
    
        Export-ModuleMember -Function Exported
    } | Import-Module -Force
    
    Describe "ModuleMockExample" {
    
        It "Hidden function is not directly accessible outside the module" {
            { Hidden } | Should Throw
        }
    
        It "Original Hidden function is called" {
            Exported | Should Be "Internal Module Function"
        }
    
        It "Hidden is replaced with our implementation" {
            Mock Hidden { "Mocked" } -ModuleName ModuleMockExample
            Exported | Should Be "Mocked"
        }
    }
    
    This example shows how calls to commands made from inside a module can be
    mocked by using the -ModuleName parameter.
    
    
    
    
    
RELATED LINKS
    Assert-MockCalled
    Assert-VerifiableMocks
    Describe
    Context
    It
    about_Should
    about_Mocking