[Time saver] Writing tests when you have long list of parameters

[wsmelton]

The main pattern we use now for the unit test we do with dbatools and Pester is the following:

Describe "$CommandName Unit Tests" -Tag 'UnitTests' {
    Context "Validate parameters" {
        [array]$params = ([Management.Automation.CommandMetaData]$ExecutionContext.SessionState.InvokeCommand.GetCommand($CommandName, 'Function')).Parameters.Keys
        [object[]]$knownParameters = <comma-separated list of parameters>

        It "Should only contain our specific parameters" {
            Compare-Object -ReferenceObject $knownParameters -DifferenceObject $params | Should -BeNullOrEmpty
        }
    }
}

We steer away from using Get-Command anymore as it has too much overhead when we have hundreds of tests to run through in Appevyor. The $knownParameters is where you will place the parameters the command has support for. We do this so we can make sure we are monitoring the parameters that get added in a given command. (If you see a command that needs a new parameter make sure to create a feature request for it 😉)

A small function I keep in my profile for writing tests so I can more easily get the initial list of parameters is to reuse a portion of what our test does as well:

function Get-CommandParameterList {
    [cmdletbinding()]
    param(
        [Parameter(Position = 0)]
        [string]
        $Command,

        [switch]
        $Raw
    )
    $keys = ([Management.Automation.CommandMetaData]$ExecutionContext.SessionState.InvokeCommand.GetCommand($Command,'Function')).Parameters.Keys
    if ($keys) {
        if ($Raw) {
            $keys
        } else {
            "'{0}'" -f ($keys -join "','")
        }
    } else {
        Write-Warning "No parmaters found for [$Command]"
    }
}

Example:

Get-CommandParameterList Connect-DbaInstance | clip -- this will copy the list to the clipboard and then I can simply paste it right into the test.