Really simple test for a database.

DatabaseTests.ps1

function Invoke-DatabaseTest
{
    param(
        [parameter(mandatory = $true)]
        [ValidateNotNullOrEmpty()]
        [String] $DatabasePort,
        [parameter(mandatory = $true)]
        [ValidateNotNullOrEmpty()]
        [String] $DatabaseName,
    )

    $Result = Invoke-Sqlcmd -Query "SELECT COUNT(*) FROM [Production].[Product]" -ConnectionString "Server=localhost,$($DatabasePort);Database=$($DatabaseName);User ID=sa;Password=ThisIsAReallyCoolPassword123;"
    if($Result.Count -lt 1)
    {
        Write-Host "No results returned!"
        exit 1
    }
}