diff --git a/test-suite/tests/ab-err-xs0006-001.xml b/test-suite/tests/ab-err-xs0006-001.xml
new file mode 100644
index 00000000..4e7f67d9
--- /dev/null
+++ b/test-suite/tests/ab-err-xs0006-001.xml
@@ -0,0 +1,34 @@
+<t:test xmlns:t="http://xproc.org/ns/testsuite/3.0"
+        xmlns:err="http://www.w3.org/ns/xproc-error"
+        expected="fail" code="err:XS0006">
+<t:info>
+  <t:title>Test ab-err-xs0006-001</t:title>
+  <t:revision-history>
+    <t:revision>
+      <t:date>2025-01-03</t:date>
+      <t:author>
+        <t:name>Achim Berndzen</t:name>
+      </t:author>
+      <t:description xmlns="http://www.w3.org/1999/xhtml">
+        <p>Initial commit.</p>
+      </t:description>
+    </t:revision>
+  </t:revision-history>
+</t:info>
+<t:description xmlns="http://www.w3.org/1999/xhtml">
+  <p>Tests that <code>err:XS0006</code> is raised.</p>
+</t:description>
+
+<t:pipeline>
+  <p:declare-step xmlns:p="http://www.w3.org/ns/xproc"
+                  xmlns:ex="http://test"
+                  version="3.0">
+    <p:output port="result"/>
+
+    <p:identity>
+      <p:with-input><doc /></p:with-input>
+    </p:identity>
+    <p:sink />
+  </p:declare-step>
+</t:pipeline>
+</t:test>
diff --git a/test-suite/tests/ab-err-xs0006-002.xml b/test-suite/tests/ab-err-xs0006-002.xml
new file mode 100644
index 00000000..d1d7c61f
--- /dev/null
+++ b/test-suite/tests/ab-err-xs0006-002.xml
@@ -0,0 +1,36 @@
+<t:test xmlns:t="http://xproc.org/ns/testsuite/3.0"
+        xmlns:err="http://www.w3.org/ns/xproc-error"
+        expected="fail" code="err:XS0006">
+<t:info>
+  <t:title>Test ab-err-xs0006-002</t:title>
+  <t:revision-history>
+    <t:revision>
+      <t:date>2025-01-03</t:date>
+      <t:author>
+        <t:name>Achim Berndzen</t:name>
+      </t:author>
+      <t:description xmlns="http://www.w3.org/1999/xhtml">
+        <p>Initial commit.</p>
+      </t:description>
+    </t:revision>
+  </t:revision-history>
+</t:info>
+<t:description xmlns="http://www.w3.org/1999/xhtml">
+  <p>Tests that <code>err:XS0006</code> is raised.</p>
+</t:description>
+
+<t:pipeline>
+  <p:declare-step xmlns:p="http://www.w3.org/ns/xproc"
+                  xmlns:ex="http://test"
+                  version="3.0">
+    <p:output port="result"><result /></p:output>
+    
+    <p:for-each>
+      <p:with-input><source /></p:with-input>
+      <p:output port="result" />
+      <p:sink />
+    </p:for-each>
+    
+  </p:declare-step>
+</t:pipeline>
+</t:test>
diff --git a/test-suite/tests/ab-err-xs0006-003.xml b/test-suite/tests/ab-err-xs0006-003.xml
new file mode 100644
index 00000000..818cbdef
--- /dev/null
+++ b/test-suite/tests/ab-err-xs0006-003.xml
@@ -0,0 +1,47 @@
+<t:test xmlns:t="http://xproc.org/ns/testsuite/3.0"
+        xmlns:err="http://www.w3.org/ns/xproc-error"
+        expected="fail" code="err:XS0006">
+<t:info>
+  <t:title>Test ab-err-xs0006-003</t:title>
+  <t:revision-history>
+    <t:revision>
+      <t:date>2025-01-03</t:date>
+      <t:author>
+        <t:name>Achim Berndzen</t:name>
+      </t:author>
+      <t:description xmlns="http://www.w3.org/1999/xhtml">
+        <p>Initial commit.</p>
+      </t:description>
+    </t:revision>
+  </t:revision-history>
+</t:info>
+<t:description xmlns="http://www.w3.org/1999/xhtml">
+  <p>Tests that <code>err:XS0006</code> is raised.</p>
+</t:description>
+
+<t:pipeline>
+  <p:declare-step xmlns:p="http://www.w3.org/ns/xproc"
+    xmlns:ex="http://test"
+    version="3.0">
+    <p:output port="result"><result /></p:output>
+    
+    <p:identity>
+      <p:with-input><source /></p:with-input>
+    </p:identity>
+    
+    <p:choose>
+      <p:when test="true()">
+        <p:output port="result" />
+        <p:sink />
+      </p:when>
+      <p:otherwise>
+        <p:output port="result" />
+        <p:identity>
+          <p:with-input><otherwise /></p:with-input>
+        </p:identity>
+      </p:otherwise>
+    </p:choose>
+    
+  </p:declare-step>
+</t:pipeline>
+</t:test>
diff --git a/test-suite/tests/ab-err-xs0006-004.xml b/test-suite/tests/ab-err-xs0006-004.xml
new file mode 100644
index 00000000..3a65bda3
--- /dev/null
+++ b/test-suite/tests/ab-err-xs0006-004.xml
@@ -0,0 +1,47 @@
+<t:test xmlns:t="http://xproc.org/ns/testsuite/3.0"
+        xmlns:err="http://www.w3.org/ns/xproc-error"
+        expected="fail" code="err:XS0006">
+<t:info>
+  <t:title>Test ab-err-xs0006-004</t:title>
+  <t:revision-history>
+    <t:revision>
+      <t:date>2025-01-03</t:date>
+      <t:author>
+        <t:name>Achim Berndzen</t:name>
+      </t:author>
+      <t:description xmlns="http://www.w3.org/1999/xhtml">
+        <p>Initial commit.</p>
+      </t:description>
+    </t:revision>
+  </t:revision-history>
+</t:info>
+<t:description xmlns="http://www.w3.org/1999/xhtml">
+  <p>Tests that <code>err:XS0006</code> is raised.</p>
+</t:description>
+
+<t:pipeline>
+  <p:declare-step xmlns:p="http://www.w3.org/ns/xproc"
+    xmlns:ex="http://test"
+    version="3.0">
+    <p:output port="result"><result /></p:output>
+    
+    <p:identity>
+      <p:with-input><source /></p:with-input>
+    </p:identity>
+    
+    <p:choose>
+      <p:when test="true()">
+        <p:output port="result" />
+        <p:identity>
+          <p:with-input><otherwise /></p:with-input>
+        </p:identity>
+      </p:when>
+      <p:otherwise>
+        <p:output port="result" />
+        <p:sink />
+      </p:otherwise>
+    </p:choose>
+    
+  </p:declare-step>
+</t:pipeline>
+</t:test>
diff --git a/test-suite/tests/ab-err-xs0006-005.xml b/test-suite/tests/ab-err-xs0006-005.xml
new file mode 100644
index 00000000..bb1d04b4
--- /dev/null
+++ b/test-suite/tests/ab-err-xs0006-005.xml
@@ -0,0 +1,38 @@
+<t:test xmlns:t="http://xproc.org/ns/testsuite/3.0"
+        xmlns:err="http://www.w3.org/ns/xproc-error"
+        expected="fail" code="err:XS0006">
+<t:info>
+  <t:title>Test ab-err-xs0006-005</t:title>
+  <t:revision-history>
+    <t:revision>
+      <t:date>2025-01-03</t:date>
+      <t:author>
+        <t:name>Achim Berndzen</t:name>
+      </t:author>
+      <t:description xmlns="http://www.w3.org/1999/xhtml">
+        <p>Initial commit.</p>
+      </t:description>
+    </t:revision>
+  </t:revision-history>
+</t:info>
+<t:description xmlns="http://www.w3.org/1999/xhtml">
+  <p>Tests that <code>err:XS0006</code> is raised.</p>
+</t:description>
+
+<t:pipeline>
+  <p:declare-step xmlns:p="http://www.w3.org/ns/xproc"
+    xmlns:ex="http://test"
+    version="3.0">
+    <p:output port="result"><result /></p:output>
+    
+    <p:group>
+      <p:output port="result" />
+      <p:identity>
+        <p:with-input><doc /></p:with-input>
+      </p:identity>
+      <p:sink />
+    </p:group>
+    
+  </p:declare-step>
+</t:pipeline>
+</t:test>
diff --git a/test-suite/tests/ab-err-xs0006-006.xml b/test-suite/tests/ab-err-xs0006-006.xml
new file mode 100644
index 00000000..dc6af713
--- /dev/null
+++ b/test-suite/tests/ab-err-xs0006-006.xml
@@ -0,0 +1,38 @@
+<t:test xmlns:t="http://xproc.org/ns/testsuite/3.0"
+        xmlns:err="http://www.w3.org/ns/xproc-error"
+        expected="fail" code="err:XS0006">
+<t:info>
+  <t:title>Test ab-err-xs0006-006</t:title>
+  <t:revision-history>
+    <t:revision>
+      <t:date>2025-01-04</t:date>
+      <t:author>
+        <t:name>Achim Berndzen</t:name>
+      </t:author>
+      <t:description xmlns="http://www.w3.org/1999/xhtml">
+        <p>Initial commit.</p>
+      </t:description>
+    </t:revision>
+  </t:revision-history>
+</t:info>
+<t:description xmlns="http://www.w3.org/1999/xhtml">
+  <p>Tests that <code>err:XS0006</code> is raised.</p>
+</t:description>
+
+<t:pipeline>
+  <p:declare-step xmlns:p="http://www.w3.org/ns/xproc"
+    xmlns:ex="http://test"
+    version="3.0">
+    <p:output port="result"><result /></p:output>
+    
+    <p:identity>
+      <p:with-input><source /></p:with-input>
+    </p:identity>
+    
+    <p:viewport match="*">
+      <p:sink />
+    </p:viewport>
+    
+  </p:declare-step>
+</t:pipeline>
+</t:test>
diff --git a/test-suite/tests/ab-err-xs0006-007.xml b/test-suite/tests/ab-err-xs0006-007.xml
new file mode 100644
index 00000000..d7ad623d
--- /dev/null
+++ b/test-suite/tests/ab-err-xs0006-007.xml
@@ -0,0 +1,39 @@
+<t:test xmlns:t="http://xproc.org/ns/testsuite/3.0"
+        xmlns:err="http://www.w3.org/ns/xproc-error"
+        expected="fail" code="err:XS0006">
+<t:info>
+  <t:title>Test ab-err-xs0006-007</t:title>
+  <t:revision-history>
+    <t:revision>
+      <t:date>2025-01-04</t:date>
+      <t:author>
+        <t:name>Achim Berndzen</t:name>
+      </t:author>
+      <t:description xmlns="http://www.w3.org/1999/xhtml">
+        <p>Initial commit.</p>
+      </t:description>
+    </t:revision>
+  </t:revision-history>
+</t:info>
+<t:description xmlns="http://www.w3.org/1999/xhtml">
+  <p>Tests that <code>err:XS0006</code> is raised.</p>
+</t:description>
+
+<t:pipeline>
+  <p:declare-step xmlns:p="http://www.w3.org/ns/xproc"
+    xmlns:ex="http://test"
+    version="3.0">
+    <p:output port="result"><result /></p:output>
+    
+    <p:identity>
+      <p:with-input><source /></p:with-input>
+    </p:identity>
+    
+    <p:viewport match="*">
+      <p:output port="result" />
+      <p:sink />
+    </p:viewport>
+    
+  </p:declare-step>
+</t:pipeline>
+</t:test>
diff --git a/test-suite/tests/ab-err-xs0006-008.xml b/test-suite/tests/ab-err-xs0006-008.xml
new file mode 100644
index 00000000..0b0143a6
--- /dev/null
+++ b/test-suite/tests/ab-err-xs0006-008.xml
@@ -0,0 +1,44 @@
+<t:test xmlns:t="http://xproc.org/ns/testsuite/3.0"
+        xmlns:err="http://www.w3.org/ns/xproc-error"
+        expected="fail" code="err:XS0006">
+<t:info>
+  <t:title>Test ab-err-xs0006-008</t:title>
+  <t:revision-history>
+    <t:revision>
+      <t:date>2025-01-04</t:date>
+      <t:author>
+        <t:name>Achim Berndzen</t:name>
+      </t:author>
+      <t:description xmlns="http://www.w3.org/1999/xhtml">
+        <p>Initial commit.</p>
+      </t:description>
+    </t:revision>
+  </t:revision-history>
+</t:info>
+<t:description xmlns="http://www.w3.org/1999/xhtml">
+  <p>Tests that <code>err:XS0006</code> is raised.</p>
+</t:description>
+
+<t:pipeline>
+  <p:declare-step xmlns:p="http://www.w3.org/ns/xproc"
+    xmlns:ex="http://test"
+    version="3.0">
+    <p:output port="result"><result /></p:output>
+    
+    <p:identity>
+      <p:with-input><source /></p:with-input>
+    </p:identity>
+    
+    <p:try>
+      <p:output port="result" />
+      <p:sink />
+      
+      <p:catch>
+        <p:output port="result" />
+        <p:identity />
+      </p:catch>
+    </p:try>
+    
+  </p:declare-step>
+</t:pipeline>
+</t:test>
diff --git a/test-suite/tests/ab-err-xs0006-009.xml b/test-suite/tests/ab-err-xs0006-009.xml
new file mode 100644
index 00000000..33e821bf
--- /dev/null
+++ b/test-suite/tests/ab-err-xs0006-009.xml
@@ -0,0 +1,44 @@
+<t:test xmlns:t="http://xproc.org/ns/testsuite/3.0"
+        xmlns:err="http://www.w3.org/ns/xproc-error"
+        expected="fail" code="err:XS0006">
+<t:info>
+  <t:title>Test ab-err-xs0006-009</t:title>
+  <t:revision-history>
+    <t:revision>
+      <t:date>2025-01-04</t:date>
+      <t:author>
+        <t:name>Achim Berndzen</t:name>
+      </t:author>
+      <t:description xmlns="http://www.w3.org/1999/xhtml">
+        <p>Initial commit.</p>
+      </t:description>
+    </t:revision>
+  </t:revision-history>
+</t:info>
+<t:description xmlns="http://www.w3.org/1999/xhtml">
+  <p>Tests that <code>err:XS0006</code> is raised.</p>
+</t:description>
+
+<t:pipeline>
+  <p:declare-step xmlns:p="http://www.w3.org/ns/xproc"
+    xmlns:ex="http://test"
+    version="3.0">
+    <p:output port="result"><result /></p:output>
+    
+    <p:identity>
+      <p:with-input><source /></p:with-input>
+    </p:identity>
+    
+    <p:try>
+      <p:output port="result" />
+      <p:identity />
+      
+      <p:catch>
+        <p:output port="result" />
+        <p:sink />
+      </p:catch>
+    </p:try>
+    
+  </p:declare-step>
+</t:pipeline>
+</t:test>