diff --git a/toolchains/xslt-M4/compose/testing/4_pruning/input/pruning001.xml b/toolchains/xslt-M4/compose/testing/4_pruning/input/pruning001.xml
new file mode 100644
index 000000000..1f330a6a9
--- /dev/null
+++ b/toolchains/xslt-M4/compose/testing/4_pruning/input/pruning001.xml
@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<METASCHEMA xmlns="http://csrc.nist.gov/ns/oscal/metaschema/1.0"
+    module="pruning001">
+    <define-assembly name="box">
+        <formal-name>BOX</formal-name>
+        <description>Just a box, no relationship to anything else.</description>
+        <root-name>BOX</root-name>
+    </define-assembly>
+</METASCHEMA>
\ No newline at end of file
diff --git a/toolchains/xslt-M4/compose/testing/4_pruning/input/pruning002.xml b/toolchains/xslt-M4/compose/testing/4_pruning/input/pruning002.xml
new file mode 100644
index 000000000..b12282240
--- /dev/null
+++ b/toolchains/xslt-M4/compose/testing/4_pruning/input/pruning002.xml
@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<METASCHEMA xmlns="http://csrc.nist.gov/ns/oscal/metaschema/1.0"
+    module="pruning002">
+    <define-assembly name="box">
+        <formal-name>BOX</formal-name>
+        <description>Just a box, no relationship to anything else.</description>
+        <root-name>BOX</root-name>
+        <model>
+            <assembly ref="folder"/>
+        </model>
+    </define-assembly>
+    <define-assembly name="folder">
+        <formal-name>Folder</formal-name>
+        <description>One or more folders belong in a box.</description>
+    </define-assembly>
+</METASCHEMA>
\ No newline at end of file
diff --git a/toolchains/xslt-M4/compose/testing/4_pruning/input/pruning003.xml b/toolchains/xslt-M4/compose/testing/4_pruning/input/pruning003.xml
new file mode 100644
index 000000000..5d86d8432
--- /dev/null
+++ b/toolchains/xslt-M4/compose/testing/4_pruning/input/pruning003.xml
@@ -0,0 +1,14 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<METASCHEMA xmlns="http://csrc.nist.gov/ns/oscal/metaschema/1.0" 
+    module="pruning003">
+    <define-assembly name="box">
+        <formal-name>BOX</formal-name>
+        <description>Just a box, no relationship to anything else.</description>
+        <root-name>BOX</root-name>
+        <model/>
+    </define-assembly>
+    <define-assembly name="folder">
+        <formal-name>Folder</formal-name>
+        <description>One or more folders belong in a box.</description>
+    </define-assembly>
+</METASCHEMA>
\ No newline at end of file
diff --git a/toolchains/xslt-M4/compose/testing/4_pruning/metaschema-prune-unused-definitions.xspec b/toolchains/xslt-M4/compose/testing/4_pruning/metaschema-prune-unused-definitions.xspec
new file mode 100644
index 000000000..662ff934b
--- /dev/null
+++ b/toolchains/xslt-M4/compose/testing/4_pruning/metaschema-prune-unused-definitions.xspec
@@ -0,0 +1,32 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<x:description 
+    xmlns:xs="http://www.w3.org/2001/XMLSchema"
+    xmlns:x="http://www.jenitennison.com/xslt/xspec"
+    xmlns:m="http://csrc.nist.gov/ns/oscal/metaschema/1.0"
+    xmlns="http://csrc.nist.gov/ns/oscal/metaschema/1.0"
+    stylesheet="../../metaschema-prune-unused-definitions.xsl"
+    run-as="external">
+    <x:scenario label="During Metaschema composition">
+        <x:scenario label="during the pruning phase">
+            <x:scenario label="a single root assembly with no references">
+                <x:context href="./input/pruning001.xml"/>
+                <x:expect label="should not throw an exception"
+                    test="$x:result//m:EXCEPTION => empty()"/>
+            </x:scenario>
+            <x:scenario label="top-level definitions with correct references.">
+                <x:context href="./input/pruning002.xml"/>
+                <x:expect label="should not throw an exception"
+                    test="$x:result//m:EXCEPTION => empty()"/>
+            </x:scenario>
+            <x:scenario label="top-level definitions with unused.">
+                <x:context href="./input/pruning003.xml"/>                
+                <x:expect label="throws only exception for an unused definition."
+                    test="count($x:result//m:EXCEPTION) eq 1"/>
+                <x:expect label="and should be of type unused-definition with the proper message."
+                    test="$x:result//m:EXCEPTION[@problem-type = 'unused-definition'] => exists()"/>
+                <x:expect label="and the error message indicates the specific definition that's unused."
+                    test="$x:result//m:EXCEPTION[@problem-type='unused-definition'] = 'REMOVING unused assembly definition for ''folder'' from pruning003'"/>
+            </x:scenario>
+        </x:scenario>
+    </x:scenario>
+</x:description>