diff --git a/.gitmodules b/.gitmodules
index 04020c84d..696341067 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -16,3 +16,6 @@
 [submodule "src/monad_app_base"]
 	path = src/monad_app_base
 	url = https://msostc.visualstudio.com/DefaultCollection/PS/_git/monad_app_base
+[submodule "ext-src/pester"]
+	path = ext-src/pester
+	url = mshttps://msostc.visualstudio.com/DefaultCollection/PS/_git/Pester
diff --git a/ext-src/pester b/ext-src/pester
new file mode 160000
index 000000000..941efb9fb
--- /dev/null
+++ b/ext-src/pester
@@ -0,0 +1 @@
+Subproject commit 941efb9fbfb56c0ffa5470b150dc7ca9c2ab350b
diff --git a/scripts/Makefile b/scripts/Makefile
index 422b3a627..df2abca4c 100644
--- a/scripts/Makefile
+++ b/scripts/Makefile
@@ -150,6 +150,7 @@ internal-prepare-exec_env: runps.sh
 	cp -r dotnetlibs/*.exe exec_env/app_base
 	cp -r dotnetlibs/lib* exec_env/app_base
 	cp -r dotnetlibs/corerun exec_env/app_base
+	cp -r ../ext-src/pester exec_env/app_base/Modules/Pester
 	cp runps.sh exec_env/app_base
 
 run: $(POWERSHELL_RUN_TARGETS) dotnetlibs/corerun dotnetlibs/Microsoft.PowerShell.Commands.Management.dll dotnetlibs/Microsoft.PowerShell.Commands.Utility.dll dotnetlibs/Microsoft.PowerShell.Security.dll dotnetlibs/api-ms-win-core-registry-l1-1-0.dll internal-prepare-exec_env
diff --git a/scripts/pester/Get-HelloWorld.Tests.ps1 b/scripts/pester/Get-HelloWorld.Tests.ps1
new file mode 100644
index 000000000..eac96930e
--- /dev/null
+++ b/scripts/pester/Get-HelloWorld.Tests.ps1
@@ -0,0 +1,13 @@
+"starting test script" | out-host
+
+$here = Split-Path -Parent $MyInvocation.MyCommand.Path
+$here | out-host
+$sut = (Split-Path -Leaf $MyInvocation.MyCommand.Path).Replace(".Tests.", ".")
+$sut | out-host
+. "$here\$sut"
+ 
+Describe "Get-HelloWorld" {
+    It "outputs 'Hello world!'" {
+        Get-HelloWorld | Should Be 'Hello world!'
+    }
+}
diff --git a/scripts/pester/Get-HelloWorld.ps1 b/scripts/pester/Get-HelloWorld.ps1
new file mode 100644
index 000000000..c89b09a96
--- /dev/null
+++ b/scripts/pester/Get-HelloWorld.ps1
@@ -0,0 +1,3 @@
+function Get-HelloWorld {
+   'Hello world!'
+}
diff --git a/src/monad b/src/monad
index 2ba6fb929..09cd9551a 160000
--- a/src/monad
+++ b/src/monad
@@ -1 +1 @@
-Subproject commit 2ba6fb9291bdb9bfea111369a6c236475bd3c686
+Subproject commit 09cd9551a2caebecc843b84e01aad7126ed7197a