feat: Added documentation for Bicep post-deployment tests (#713)

Author: AlexanderSehr

docs/content/specs/bicep/_index.md

@@ -524,3 +524,62 @@ Example - `AVM Module Issue template` module name entry for the Bicep resource m
 ---
 
 <br>
+
+#### ID: BCPNFR16 - Category: Testing - Post-deployment tests
+
+For each test case in the `e2e` folder, you can optionally add post-deployment Pester tests that are executed once the corresponding deployment completed and before the removal logic kicks in.
+
+To leverage the feature you must
+- Use Pester as a test framework in each test file
+- Name the file with the suffix `"*.tests.ps1"`
+- Place each test file the `e2e` test's folder or any subfolder (e.g., `e2e/max/myTest.tests.ps1` or `e2e/max/tests/myTest.tests.ps1`)
+- Implement an input parameter `TestInputData` in the following way:
+  ```pwsh
+  param (
+      [Parameter(Mandatory = $false)]
+      [hashtable] $TestInputData = @{}
+  )
+  ```
+  Through this parameter you can make use of every output the `main.test.bicep` file returns, as well as the path to the test template file in case you want to extract data from it directly.
+
+  For example, with an output such as `output resourceId string = testDeployment[1].outputs.resourceId` defined in the `main.test.bicep` file, the `$TestInputData` would look like
+  ```pwsh
+  $TestInputData = @{
+    DeploymentOutputs    = @{
+      resourceId = @{
+        Type  = "String"
+        Value = "/subscriptions/***/resourceGroups/dep-***-keyvault.vaults-kvvpe-rg/providers/Microsoft.KeyVault/vaults/***kvvpe001"
+      }
+    }
+    ModuleTestFolderPath = "/home/runner/work/bicep-registry-modules/bicep-registry-modules/avm/res/key-vault/vault/tests/e2e/private-endpoint"
+  }
+  ```
+  A full test file may look like
+
+  {{< expand "➕ Pester post-deployment test file example" "expand/collapse">}}
+
+  ```pwsh
+  param (
+      [Parameter(Mandatory = $false)]
+      [hashtable] $TestInputData = @{}
+  )
+
+  Describe 'Validate private endpoint deployment' {
+
+      Context 'Validate sucessful deployment' {
+
+          It "Private endpoints should be deployed in resource group" {
+
+              $keyVaultResourceId = $TestInputData.DeploymentOutputs.resourceId.Value
+              $testResourceGroup = ($keyVaultResourceId -split '\/')[4]
+              $deployedPrivateEndpoints = Get-AzPrivateEndpoint -ResourceGroupName   $testResourceGroup
+              $deployedPrivateEndpoints.Count | Should -BeGreaterThan 0
+          }
+      }
+  }
+  ```
+  {{< /expand >}}
+
+---
+
+<br>