Do not cleanup previous mocks in inner Invoke-Pester

src/Main.ps1

@@ -638,16 +638,17 @@ function Invoke-Pester {
         # this will inherit to child scopes and allow Describe / Context to run directly from a file or command line
         $invokedViaInvokePester = $true
 
+        if ($null -eq $state) {
+            # Cleanup any leftover mocks from previous runs, but only if we are not running in a nested Pester-run
+            # todo: move mock cleanup to BeforeAllBlockContainer when there is any?
+            Remove-MockFunctionsAndAliases -SessionState $PSCmdlet.SessionState
+        }
+
         # this will inherit to child scopes and allow Pester to run in Pester, not checking if this is
         # already defined because we want a clean state for this Invoke-Pester even if it runs inside another
         # testrun (which calls Invoke-Pester itself)
         $state = New-PesterState
 
-        # TODO: Remove all references to mock table, there should not be many.
-        $script:mockTable = @{}
-        # todo: move mock cleanup to BeforeAllBlockContainer when there is any
-        Remove-MockFunctionsAndAliases -SessionState $PSCmdlet.SessionState
-
         # store CWD so we can revert any changes at the end
         $initialPWD = $pwd.Path
     }

src/functions/Pester.SessionState.Mock.ps1

@@ -1195,7 +1195,9 @@ function Invoke-Mock {
     # if we are targeting a module use the behaviors for the current module, but if there is no default the fall back to the non-module default behavior.
     # do not fallback to non-module filtered behaviors. This is here for safety, and for compatibility when doing Mock Remove-Item {}, and then mocking in module
     # then the default mock for Remove-Item should be effective.
-    $behaviors = if ($targettingAModule) {
+
+    # using @() to always get array. This avoids null error in Invoke-MockInternal when no behaviors where found (if-else unwraps the lists)
+    $behaviors = @(if ($targettingAModule) {
         # we have default module behavior add it to the filtered behaviors if there are any
         if ($null -ne $moduleDefaultBehavior) {
             $moduleBehaviors.Add($moduleDefaultBehavior)
@@ -1217,7 +1219,7 @@ function Invoke-Mock {
         }
 
         $nonModuleBehaviors
-    }
+    })
 
     $callHistory = (Get-MockDataForCurrentScope).CallHistory
 

tst/functions/Mock.Tests.ps1

@@ -1287,9 +1287,6 @@ Describe 'Dot Source Test' {
     }
 
     It "Doesn't call the mock with any other parameters" {
-        InPesterModuleScope {
-            $global:calls = $mockTable['||Test-Path'].CallHistory
-        }
         Should -Invoke Test-Path -Exactly 0 -ParameterFilter { $Path -ne 'Test' } -Scope Describe
     }
 }
@@ -3138,3 +3135,38 @@ Describe 'Mocking in manifest modules' {
         Should -Invoke -CommandName 'myManifestPrivateFunction' -ModuleName $moduleName -Exactly -Times 1
     }
 }
+
+Describe 'Mocking with nested Pester runs' {
+    BeforeAll {
+        Mock Get-Date { 1 }
+
+        $innerRun = Invoke-Pester -Container (New-PesterContainer -ScriptBlock {
+                Describe 'inner' {
+                    It 'local mock works' {
+                        Mock Get-Command { 2 }
+                        Get-Command | Should -Be 2
+                    }
+
+                    It 'outer mock is not available' {
+                        Get-Date | Should -Not -Be 1
+                    }
+                }
+            }) -Output None -PassThru
+    }
+
+    It 'Mocks in outer run works after nested Invoke-Pester' {
+        # https://github.com/pester/Pester/issues/2074
+        Get-Date | Should -Be 1
+        # Outer mock should not have been called from nested run
+        Should -Invoke Get-Date -Exactly -Times 1
+    }
+
+    It 'Mocking works in nested run' {
+        $innerRun.Result | Should -Be 'Passed'
+        $innerRun.PassedCount | Should -Be 2
+    }
+
+    It 'Mocks in nested run do not leak to outside' {
+        Get-Command Get-ChildItem | Should -Not -Be 2
+    }
+}