diff --git a/Tests/Unit/Test-FeaturesJson.ps1 b/Tests/Unit/Test-FeaturesJson.ps1
index 517f56d..caafa1e 100644
--- a/Tests/Unit/Test-FeaturesJson.ps1
+++ b/Tests/Unit/Test-FeaturesJson.ps1
@@ -137,4 +137,42 @@ Describe 'Features.json' {
             $feature.RequiresRestorePoint | Should -BeTrue
         }
     }
+
+    It 'gives every feature a category that is defined' {
+        # The GUI groups cards by category. A feature naming a category that does
+        # not exist has no column to render in. A null category is allowed: those
+        # are the CLI-only pseudo-features that are not shown as cards.
+        $categoryNames = @($script:json.Categories.Name)
+        $orphans = @($script:features | Where-Object { $_.Category -and $_.Category -notin $categoryNames } |
+                ForEach-Object { "$($_.FeatureId) -> $($_.Category)" })
+        $orphans | Should -BeNullOrEmpty -Because "features naming a category that is not defined: $($orphans -join '; ')"
+    }
+
+    It 'wires every UiGroup to real features and a real category' {
+        # A combobox option maps to FeatureIds. If one names a feature that does
+        # not exist, selecting that option applies nothing, silently. And the
+        # group needs a category to render in, like any card.
+        $featureIds = @($script:features.FeatureId)
+        $categoryNames = @($script:json.Categories.Name)
+        $problems = New-Object System.Collections.Generic.List[string]
+
+        foreach ($group in @($script:json.UiGroups)) {
+            if ($group.Category -notin $categoryNames) {
+                $problems.Add("group $($group.GroupId) -> undefined category $($group.Category)")
+            }
+            foreach ($value in @($group.Values)) {
+                foreach ($featureId in @($value.FeatureIds)) {
+                    if ($featureId -notin $featureIds) {
+                        $problems.Add("group $($group.GroupId) -> undefined feature $featureId")
+                    }
+                    elseif ($featureId -notin $script:entryParameterNames) {
+                        $problems.Add("group $($group.GroupId) feature $featureId has no CLI parameter")
+                    }
+                }
+            }
+        }
+
+        @($script:json.UiGroups).Count | Should -BeGreaterThan 0 -Because 'the config must actually define UI groups'
+        $problems | Should -BeNullOrEmpty -Because "UiGroup wiring problems: $($problems -join '; ')"
+    }
 }
diff --git a/Tests/Unit/Test-SafetyGuards.ps1 b/Tests/Unit/Test-SafetyGuards.ps1
index 6ae4a48..10ec0cc 100644
--- a/Tests/Unit/Test-SafetyGuards.ps1
+++ b/Tests/Unit/Test-SafetyGuards.ps1
@@ -180,6 +180,41 @@ Describe 'Winnow script loading' {
                 }
             }
         }
+
+        # For each Winnow function, its declared parameters and whether it takes
+        # arbitrary arguments ($args or ValueFromRemainingArguments), plus every
+        # named argument passed to a Winnow function anywhere in the loaded code.
+        $script:functionInfo = @{}
+        $script:paramArgCalls = New-Object System.Collections.Generic.List[object]
+        foreach ($relative in @('winnow.ps1') + $script:loadedScripts) {
+            $ast = [System.Management.Automation.Language.Parser]::ParseFile((Join-Path $script:loadRoot $relative), [ref]$null, [ref]$null)
+            foreach ($definition in $ast.FindAll({ param($n) $n -is [System.Management.Automation.Language.FunctionDefinitionAst] }, $true)) {
+                $names = @()
+                if ($definition.Body.ParamBlock) { $names = @($definition.Body.ParamBlock.Parameters.Name.VariablePath.UserPath) }
+                elseif ($definition.Parameters) { $names = @($definition.Parameters.Name.VariablePath.UserPath) }
+                $body = $definition.Extent.Text
+                $script:functionInfo[$definition.Name] = [PSCustomObject]@{
+                    Params      = $names
+                    AcceptsArgs = ($body -match '\$args\b') -or ($body -match 'ValueFromRemainingArguments')
+                }
+            }
+        }
+        foreach ($relative in @('winnow.ps1') + $script:loadedScripts) {
+            $ast = [System.Management.Automation.Language.Parser]::ParseFile((Join-Path $script:loadRoot $relative), [ref]$null, [ref]$null)
+            foreach ($call in $ast.FindAll({ param($n) $n -is [System.Management.Automation.Language.CommandAst] }, $true)) {
+                $name = $call.GetCommandName()
+                if (-not $name -or -not $script:functionInfo.ContainsKey($name)) { continue }
+                foreach ($element in $call.CommandElements) {
+                    if ($element -is [System.Management.Automation.Language.CommandParameterAst]) {
+                        $script:paramArgCalls.Add([PSCustomObject]@{
+                                Function = $name
+                                Param    = $element.ParameterName
+                                Where    = ('{0}:{1}' -f $relative, $call.Extent.StartLineNumber)
+                            })
+                    }
+                }
+            }
+        }
     }
 
     It 'dot-sources every script under Scripts apart from the ones kept out by design' {
@@ -224,4 +259,26 @@ Describe 'Winnow script loading' {
         $script:commandCalls.Count | Should -BeGreaterThan 1000 -Because 'the scan must actually see the scripts'
         $unresolved | Should -BeNullOrEmpty -Because "calls that resolve to nothing: $($unresolved -join '; ')"
     }
+
+    It 'passes only declared parameters to Winnow functions' {
+        # A named argument that matches no parameter fails at run time with "A
+        # parameter cannot be found that matches parameter name". PowerShell
+        # accepts an unambiguous prefix (-Desc for -Description) and the common
+        # parameters, so both are allowed here. Functions that take $args are
+        # skipped because they accept anything.
+        $common = @('Verbose', 'Debug', 'ErrorAction', 'ErrorVariable', 'WarningAction', 'WarningVariable',
+            'InformationAction', 'InformationVariable', 'OutVariable', 'OutBuffer', 'PipelineVariable', 'WhatIf', 'Confirm')
+
+        $badArgs = @(foreach ($use in $script:paramArgCalls) {
+                $info = $script:functionInfo[$use.Function]
+                if ($info.AcceptsArgs) { continue }
+                $valid = @($info.Params) + $common
+                $lower = $use.Param.ToLowerInvariant()
+                $matches = @($valid | Where-Object { $_.ToLowerInvariant() -eq $lower -or $_.ToLowerInvariant().StartsWith($lower) })
+                if ($matches.Count -eq 0) { "$($use.Function) -$($use.Param) at $($use.Where)" }
+            })
+
+        $script:paramArgCalls.Count | Should -BeGreaterThan 0 -Because 'the scan must see named arguments'
+        $badArgs | Should -BeNullOrEmpty -Because "parameters that match nothing: $($badArgs -join '; ')"
+    }
 }