. $PSScriptRoot\..\..\Load-PesterModules.ps1
$here = Split-Path -Parent $MyInvocation.MyCommand.Path
$sut = (Split-Path -Leaf $MyInvocation.MyCommand.Path) -replace '\.tests\.', '.'
$functionPath = Join-Path -Path $here -ChildPath $sut
Write-Host "Overriding SUT: $functionPath"
Import-Module $functionPath -Force
$moduleForMock = ""

Describe "Get-CoalescedStringValue" {

    Context "Logic" {

        It "Returns ValueA if it Is Not Null, Empty, or WhiteSpace" {

            $valueA = "I am the very model"
            $valueB = "of a modern Major-General"
            Get-CoalescedStringValue -ValueA $valueA -ValueB $valueB | Should Be $valueA
        }

        It "Returns ValueB if ValueA is Null" {

            $valueA = $null
            $valueB = "I've information vegetable, animal, and mineral"
            Get-CoalescedStringValue -ValueA $valueA -ValueB $valueB | Should Be $valueB
        }

        It "Returns ValueB if ValueA is Whitespace" {

            $valueA = "                "
            $valueB = "I know the kings of England, and I quote the fights Historical"
            Get-CoalescedStringValue -ValueA $valueA -ValueB $valueB | Should Be $valueB
        }

        It "Returns ValueB if ValueA is an Empty String" {

            $valueA = ""
            $valueB = "From Marathon to Waterloo, in order categorical"
            Get-CoalescedStringValue -ValueA $valueA -ValueB $valueB | Should Be $valueB
        }
    }

    Context "Edge Cases" {

        It "Returns an empty string and Writes a Warning if ValueA and ValueB are Both Null" {

            Mock -CommandName Write-Warning -ModuleName $moduleForMock -MockWith {}

            $valueA = $null
            $valueB = $null
            Get-CoalescedStringValue -ValueA $valueA -ValueB $valueB | Should Be ([String]::Empty)
            Assert-MockCalled -ModuleName $moduleForMock -CommandName Write-Warning -Times 1 -Exactly -Scope It `
                -ParameterFilter { $Message -Match "Value B is null, empty, or whitespace." }
        }

        It "Returns ValueB and Writes a Warning if ValueA is null and ValueB is Whitespace" {

            Mock -CommandName Write-Warning -ModuleName $moduleForMock -MockWith {}

            $valueA = $null
            $valueB = "              "
            Get-CoalescedStringValue -ValueA $valueA -ValueB $valueB | Should Be $valueB
            Assert-MockCalled -ModuleName $moduleForMock -CommandName Write-Warning -Times 1 -Exactly -Scope It `
                -ParameterFilter { $Message -Match "Value B is null, empty, or whitespace." }
        }

        It "Returns ValueB and Writes a Warning if ValueA is null and ValueB is an Empty String" {

            Mock -CommandName Write-Warning -ModuleName $moduleForMock -MockWith {}

            $valueA = $null
            $valueB = ""
            Get-CoalescedStringValue -ValueA $valueA -ValueB $valueB | Should Be $valueB
            Assert-MockCalled -ModuleName $moduleForMock -CommandName Write-Warning -Times 1 -Exactly -Scope It `
                -ParameterFilter { $Message -Match "Value B is null, empty, or whitespace." }
        }
    }
}