diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 2fbc339..64e2d38 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -203,6 +203,15 @@ jobs:
             exit 1
           }
 
+      - name: Run GUI control state tests
+        shell: pwsh
+        run: |
+          $result = Invoke-Pester -Path "Tests/Unit/Test-GuiControlState.ps1" -Output Detailed -PassThru
+          if ($result.FailedCount -gt 0) {
+            Write-Error "$($result.FailedCount) test(s) failed in Test-GuiControlState.ps1"
+            exit 1
+          }
+
       - name: Run Store search suggestion tests
         shell: pwsh
         run: |
diff --git a/Tests/Unit/Test-GuiControlState.ps1 b/Tests/Unit/Test-GuiControlState.ps1
new file mode 100644
index 0000000..f6ff7d1
--- /dev/null
+++ b/Tests/Unit/Test-GuiControlState.ps1
@@ -0,0 +1,142 @@
+#Requires -Modules Pester
+<#
+.SYNOPSIS
+    Unit tests for GUI helpers that operate on live WPF controls.
+.DESCRIPTION
+    ConvertTo-NormalizedCheckboxState, Set-TriStatePresetCheckBoxState, and
+    Test-ComboBoxContainsMatch take real CheckBox and ComboBox objects, so they
+    cannot be exercised with a plain data stand-in. Each scenario builds the
+    control, calls the function, and returns the resulting state.
+
+    WPF construction needs a single-threaded apartment; the unit suite runs
+    under pwsh, which is multi-threaded, so every scenario runs in its own STA
+    runspace. The runspace shares this process, so the returned hashtable holds
+    real values, not serialized copies.
+#>
+
+BeforeAll {
+    $script:repoRoot = Resolve-Path (Join-Path $PSScriptRoot '..\..') | Select-Object -ExpandProperty Path
+
+    function Invoke-InStaRunspace {
+        param(
+            [Parameter(Mandatory)][scriptblock]$Script,
+            [object[]]$ArgumentList = @()
+        )
+        $runspace = [runspacefactory]::CreateRunspace()
+        $runspace.ApartmentState = 'STA'
+        $runspace.ThreadOptions = 'ReuseThread'
+        $runspace.Open()
+        try {
+            $shell = [powershell]::Create()
+            $shell.Runspace = $runspace
+            [void]$shell.AddScript($Script.ToString())
+            foreach ($argument in $ArgumentList) { [void]$shell.AddArgument($argument) }
+            $output = $shell.Invoke()
+            if ($shell.HadErrors) {
+                throw (($shell.Streams.Error | ForEach-Object { $_.ToString() }) -join '; ')
+            }
+            $shell.Dispose()
+            return $output[-1]
+        }
+        finally {
+            $runspace.Dispose()
+        }
+    }
+
+    # Runs against MainWindow-AppSelection.ps1 loaded inside the STA runspace.
+    $script:appSelectionScenario = {
+        param($repoRoot, $case)
+        Add-Type -AssemblyName PresentationFramework, PresentationCore, WindowsBase -ErrorAction Stop
+        . (Join-Path $repoRoot 'Scripts\GUI\MainWindow-AppSelection.ps1')
+
+        switch ($case) {
+            'normalize-indeterminate' {
+                $cb = New-Object System.Windows.Controls.CheckBox
+                $cb.IsThreeState = $true
+                $cb | Add-Member -NotePropertyName WasIndeterminateBeforeClick -NotePropertyValue $true -Force
+                $cb.IsChecked = $false
+                $result = ConvertTo-NormalizedCheckboxState -CheckBox $cb
+                return @{ Result = $result; IsChecked = $cb.IsChecked; StillFlagged = $cb.WasIndeterminateBeforeClick }
+            }
+            'normalize-checked' {
+                $cb = New-Object System.Windows.Controls.CheckBox
+                $cb.IsChecked = $true
+                return @{ Result = (ConvertTo-NormalizedCheckboxState -CheckBox $cb) }
+            }
+            'normalize-unchecked' {
+                $cb = New-Object System.Windows.Controls.CheckBox
+                $cb.IsChecked = $false
+                return @{ Result = (ConvertTo-NormalizedCheckboxState -CheckBox $cb) }
+            }
+            default {
+                # tri-state: case is "Total,Selected"
+                $parts = $case -split ','
+                $cb = New-Object System.Windows.Controls.CheckBox
+                $cb.IsThreeState = $true
+                Set-TriStatePresetCheckBoxState -CheckBox $cb -Total ([int]$parts[0]) -Selected ([int]$parts[1])
+                return @{ IsChecked = $cb.IsChecked; IsNull = ($null -eq $cb.IsChecked); IsEnabled = $cb.IsEnabled }
+            }
+        }
+    }
+
+    $script:comboScenario = {
+        param($repoRoot, $searchText)
+        Add-Type -AssemblyName PresentationFramework, PresentationCore, WindowsBase -ErrorAction Stop
+        . (Join-Path $repoRoot 'Scripts\GUI\MainWindow-TweaksBuilder.ps1')
+
+        $combo = New-Object System.Windows.Controls.ComboBox
+        $item = New-Object System.Windows.Controls.ComboBoxItem
+        $item.Content = 'Show search box'
+        [void]$combo.Items.Add($item)
+        [void]$combo.Items.Add('Hide taskbar')
+        return @{ Match = (Test-ComboBoxContainsMatch -ComboBox $combo -SearchText $searchText) }
+    }
+}
+
+Describe 'ConvertTo-NormalizedCheckboxState' {
+    It 'treats a checkbox that was indeterminate before the click as checked' {
+        $r = Invoke-InStaRunspace -Script $script:appSelectionScenario -ArgumentList @($script:repoRoot, 'normalize-indeterminate')
+        $r.Result | Should -BeTrue
+        $r.IsChecked | Should -BeTrue
+        $r.StillFlagged | Should -BeFalse -Because 'the one-shot flag is cleared'
+    }
+
+    It 'reports a checked box as checked and an unchecked box as unchecked' {
+        (Invoke-InStaRunspace -Script $script:appSelectionScenario -ArgumentList @($script:repoRoot, 'normalize-checked')).Result | Should -BeTrue
+        (Invoke-InStaRunspace -Script $script:appSelectionScenario -ArgumentList @($script:repoRoot, 'normalize-unchecked')).Result | Should -BeFalse
+    }
+}
+
+Describe 'Set-TriStatePresetCheckBoxState' {
+    It 'disables and unchecks the box when nothing is available' {
+        $r = Invoke-InStaRunspace -Script $script:appSelectionScenario -ArgumentList @($script:repoRoot, '0,0')
+        $r.IsEnabled | Should -BeFalse
+        $r.IsChecked | Should -BeFalse
+    }
+
+    It 'unchecks when none selected, checks when all selected' {
+        $none = Invoke-InStaRunspace -Script $script:appSelectionScenario -ArgumentList @($script:repoRoot, '3,0')
+        $none.IsEnabled | Should -BeTrue
+        $none.IsChecked | Should -BeFalse
+
+        $all = Invoke-InStaRunspace -Script $script:appSelectionScenario -ArgumentList @($script:repoRoot, '3,3')
+        $all.IsChecked | Should -BeTrue
+    }
+
+    It 'goes indeterminate on a partial selection' {
+        $r = Invoke-InStaRunspace -Script $script:appSelectionScenario -ArgumentList @($script:repoRoot, '3,1')
+        $r.IsNull | Should -BeTrue
+        $r.IsEnabled | Should -BeTrue
+    }
+}
+
+Describe 'Test-ComboBoxContainsMatch' {
+    It 'finds a match in a ComboBoxItem and in a plain string item' {
+        (Invoke-InStaRunspace -Script $script:comboScenario -ArgumentList @($script:repoRoot, 'search')).Match | Should -BeTrue
+        (Invoke-InStaRunspace -Script $script:comboScenario -ArgumentList @($script:repoRoot, 'taskbar')).Match | Should -BeTrue
+    }
+
+    It 'returns false when no item contains the search text' {
+        (Invoke-InStaRunspace -Script $script:comboScenario -ArgumentList @($script:repoRoot, 'nonexistent')).Match | Should -BeFalse
+    }
+}