Likeness concept for Pester

gistfile1.ps1

function Assert-ValueObjectAreAlike ($ReferenceObject, $DifferenceObject, $ExcludeProperty)
{
    [string[]] $properties =  ($ReferenceObject.psObject.Properties.Name + $DifferenceObject.psObject.Properties.Name ) | 
        sort -Unique | 
        where { $_ -notlike $ExcludeProperty }

    -not ( Compare-Object -ReferenceObject $ReferenceObject -DifferenceObject $DifferenceObject  -Property $properties )
}

#usual use case
$a= [pscustomobject]@{
    a = 1
    b = 2
    c = 3
}
$b = [pscustomobject]@{
    a = 1
    b = 2
    c = 3
    d = 4 # not present on the $a
}

Assert-ValueObjectAreAlike -ReferenceObject $a -DifferenceObject $b #false

Assert-ValueObjectAreAlike -ReferenceObject $a -DifferenceObject $b -ExcludeProperty 'd' #true


#not so usual use case
$ps = ps | select -First 2
Assert-ValueObjectAreAlike -ReferenceObject $ps[0] -DifferenceObject $ps[1] #writes few errors then returns false

$b = [pscustomobject]@{
    a = 1
    b = 2
    c = 3
    d = 4
}

$d = [pscustomobject]@{
    a = 1
    b = 2
    c = 3
    d = 5
}

$a= [pscustomobject]@{
    a = 1
    b = $b
}
$c = [pscustomobject]@{
    a=1
    b=$d
}
Assert-ValueObjectAreAlike $a $c

#result working with reference types makes this very complex problem, 
#psobjects references (in properties) are considered equal by the compare-object

#related sources 
#https://github.com/AutoFixture/AutoFixture/issues/48
#http://www.nuget.org/packages/DeepEqual