Add nested re-mock pattern to repro #2829

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: nohwnd

.repro2829/repro.ps1

@@ -100,6 +100,7 @@ Import-Module (Join-Path $modDir 'ReproMod.psd1') -Force
 $container = New-PesterContainer -ScriptBlock {
     Describe 'Repro 2829' {
         BeforeAll {
+            # Describe-scope (BeforeAll) default mocks, exactly like dbatools' BeforeAll.
             Mock -CommandName Invoke-Program -ModuleName ReproMod -MockWith {
                 [PSCustomObject]@{ Successful = $true; ExitCode = [uint32[]]0 }
             }
@@ -111,11 +112,43 @@ $container = New-PesterContainer -ScriptBlock {
             # a -ParameterFilter mock, like dbatools' Get-DbaCmObject mock
             Mock -CommandName Get-Content -ModuleName ReproMod -MockWith { 'x' } -ParameterFilter { $Path -eq 'never' }
         }
-        It 'engages the -ModuleName mock reached via ForEach-Object' {
-            $result = Install-Thing -ComputerName 'HOST'
-            Should -Invoke -CommandName Invoke-Program -Exactly 1 -Scope It -ModuleName ReproMod
-            Should -Invoke -CommandName Test-PendingReboot -Exactly 1 -Scope It -ModuleName ReproMod
-            $result.Successful | Should -Be $true
+
+        Context 'Validate installs of each version' {
+            It 'A - relies on the Describe/BeforeAll mock only' {
+                $result = Install-Thing -ComputerName 'HOST'
+                Should -Invoke -CommandName Invoke-Program -Exactly 1 -Scope It -ModuleName ReproMod
+                $result.Successful | Should -Be $true
+            }
+            It 'B - re-mocks Invoke-Program inside the It (nested), like the restart/tools tests' {
+                Mock -CommandName Invoke-Program -ModuleName ReproMod -MockWith {
+                    [PSCustomObject]@{ Successful = $true; ExitCode = [uint32[]]3010 }
+                }
+                $result = Install-Thing -ComputerName 'HOST'
+                $result.ExitCode | Should -Be 3010
+            }
+            It 'C - relies on the Describe mock again AFTER a nested re-mock' {
+                $result = Install-Thing -ComputerName 'HOST'
+                $result.Successful | Should -Be $true
+                $result.ExitCode | Should -Be 0
+            }
+        }
+
+        Context 'Negative tests' {
+            It 'D - re-mocks Invoke-Program to failure then reverts, like "fails when update execution has failed"' {
+                #override default mock
+                Mock -CommandName Invoke-Program -ModuleName ReproMod -MockWith {
+                    [PSCustomObject]@{ Successful = $false; ExitCode = [uint32[]]12345 }
+                }
+                (Install-Thing -ComputerName 'HOST').Successful | Should -Be $false
+                (Install-Thing -ComputerName 'HOST').ExitCode | Should -Be 12345
+                #revert default mock
+                Mock -CommandName Invoke-Program -ModuleName ReproMod -MockWith {
+                    [PSCustomObject]@{ Successful = $true; ExitCode = [uint32[]]0 }
+                }
+            }
+            It 'E - relies on the Describe mock again AFTER the negative re-mock+revert' {
+                (Install-Thing -ComputerName 'HOST').Successful | Should -Be $true
+            }
         }
     }
 }