Proposed fix for #275

Functions/InModuleScope.ps1

@@ -68,21 +68,7 @@ function InModuleScope
         $script:mockTable = @{}
     }
 
-    try
-    {
-        $modules = @(Get-Module -Name $ModuleName -All -ErrorAction Stop)
-    }
-    catch
-    {
-        throw "No module named '$ModuleName' is currently loaded."
-    }
-
-    if ($modules.Count -gt 1)
-    {
-        throw "Multiple modules named '$ModuleName' are currently loaded.  Make sure to remove any extra copies of the module from your session before testing."
-    }
-
-    $module = $modules[0]
+    $module = Get-ScriptModule -ModuleName $ModuleName -ErrorAction Stop
 
     $originalState = $Pester.SessionState
     $originalScriptBlockScope = Get-ScriptBlockScope -ScriptBlock $ScriptBlock
@@ -101,3 +87,43 @@ function InModuleScope
         Set-ScriptBlockScope -ScriptBlock $ScriptBlock -SessionStateInternal $originalScriptBlockScope
     }
 }
+
+function Get-ScriptModule
+{
+    [CmdletBinding()]
+    param (
+        [Parameter(Mandatory = $true)]
+        [string] $ModuleName
+    )
+
+    try
+    {
+        $modules = @(Get-Module -Name $ModuleName -All -ErrorAction Stop)
+    }
+    catch
+    {
+        throw "No module named '$ModuleName' is currently loaded."
+    }
+
+    $scriptModules = @($modules | Where-Object { $_.ModuleType -eq 'Script' })
+
+    if ($scriptModules.Count -gt 1)
+    {
+        throw "Multiple Script modules named '$ModuleName' are currently loaded.  Make sure to remove any extra copies of the module from your session before testing."
+    }
+
+    if ($scriptModules.Count -eq 0)
+    {
+        $actualTypes = @(
+            $modules |
+            Where-Object { $_.ModuleType -ne 'Script' } |
+            Select-Object -ExpandProperty ModuleType -Unique
+        )
+
+        $actualTypes = $actualTypes -join ', '
+
+        throw "Module '$ModuleName' is not a Script module.  Detected modules of the following types: '$actualTypes'"
+    }
+
+    return $scriptModules[0]
+}

Functions/Mock.ps1

@@ -586,10 +586,8 @@ function Validate-Command([string]$CommandName, [string]$ModuleName) {
     }
 
     if ($ModuleName) {
-        $module = Microsoft.PowerShell.Core\Get-Module $ModuleName -All |
-                  Sort ModuleType |
-                  Where { ($origCommand = & $_ $scriptBlock $commandName) } |
-                  Select -First 1
+        $module = Get-ScriptModule -ModuleName $ModuleName -ErrorAction Stop
+        $origCommand = & $module $scriptBlock $CommandName
     }
 
     $session = $pester.SessionState
@@ -604,7 +602,7 @@ function Validate-Command([string]$CommandName, [string]$ModuleName) {
     }
 
     if ($module) {
-        $session = & @($module)[0] { $ExecutionContext.SessionState }
+        $session = & $module { $ExecutionContext.SessionState }
     }
 
     @{Command = $origCommand; Session = $session}

Pester.Tests.ps1

@@ -251,4 +251,4 @@ InModuleScope Pester {
             }
         }
     }
-}
+}