diff --git a/core/tests/unit/ldml/keyboards/ldml_test-test.xml b/core/tests/unit/ldml/keyboards/ldml_test-test.xml
index ba9630e004..a771562bda 100644
--- a/core/tests/unit/ldml/keyboards/ldml_test-test.xml
+++ b/core/tests/unit/ldml/keyboards/ldml_test-test.xml
@@ -4,29 +4,90 @@
   <info keyboard="ldml_test.xml" author="srl295" name="test" />
 
   <tests name="separate">
+    <!-- test direct key output
+    https://www.unicode.org/reports/tr35/tr35-keyboards.html#element-key -->
     <test name="key-1">
       <keystroke key="1" />
       <check result="1:basic:OK" />
     </test>
+    <!-- test a simple transform
+    https://www.unicode.org/reports/tr35/tr35-keyboards.html#element-transform -->
     <test name="key-2">
       <keystroke key="2" />
       <check result="2:simple_transform:OK" />
     </test>
+    <!-- test a transform using a marker
+    https://www.unicode.org/reports/tr35/tr35-keyboards.html#markers -->
     <test name="key-3">
       <keystroke key="3" />
       <check result="3:simple_marker:OK" />
     </test>
+    <!-- test a reorder
+    https://www.unicode.org/reports/tr35/tr35-keyboards.html#element-reorder -->
     <test name="key-4">
       <keystroke key="4" />
       <check result="4:simple_reorder:OK" />
     </test>
+    <!-- test using variable substitution
+    https://www.unicode.org/reports/tr35/tr35-keyboards.html#element-string -->
     <test name="key-5">
       <keystroke key="5" />
       <check result="5:simple_vars:OK" />
     </test>
+    <!-- test a mapped variable substitution
+    https://www.unicode.org/reports/tr35/tr35-keyboards.html#replacement-syntax -->
     <test name="key-6">
       <keystroke key="6" />
       <check result="6:map_var:OK" />
     </test>
+    <!-- test a uset substitution
+    https://www.unicode.org/reports/tr35/tr35-keyboards.html#element-unicodeset -->
+    <test name="key-7">
+      <keystroke key="7" />
+      <check result="7:simple_uset:OK" />
+    </test>
+    <!-- test a different uset substitution
+    https://www.unicode.org/reports/tr35/tr35-keyboards.html#element-unicodeset -->
+    <test name="key-shift-7">
+      <keystroke key="shift-7" />
+      <check result="7:simple_uset:FAIL" />
+    </test>
+    <!-- test pre-existing input context
+    https://www.unicode.org/reports/tr35/tr35-keyboards.html#test-element-startcontext -->
+    <test name="key-8">
+      <startContext to="ABC" />
+      <keystroke key="8" />
+      <check result="8:ctxt:OK" />
+    </test>
+    <!-- test that the input context is required
+    https://www.unicode.org/reports/tr35/tr35-keyboards.html#test-element-startcontext -->
+    <test name="key-8-fail">
+      <startContext to="" /> <!-- w/o context -->
+      <keystroke key="8" />
+      <check result="8:ctxt:FAIL"/>
+    </test>
+    <!-- test context with a non-BMP character
+    https://www.unicode.org/reports/tr35/tr35-keyboards.html#test-element-startcontext -->
+    <test name="key-8-osage">
+      <startContext to="𐓏" />
+      <keystroke key="8" />
+      <check result="8:ctxt:OK" />
+    </test>
+    <!-- test using two pieces of context together with non-BMP chars
+    https://www.unicode.org/reports/tr35/tr35-keyboards.html#test-element-startcontext -->
+    <test name="key-8-osage2">
+      <startContext to="𐒻" />
+      <keystroke key="shift-8" />
+      <keystroke key="8" />
+      <check result="8:ctxt:OK" />
+    </test>
+    <!-- test using two markers across two keystrokes
+    https://www.unicode.org/reports/tr35/tr35-keyboards.html#markers -->
+    <test name="key-9">
+      <startContext to="" />
+      <keystroke key="9" />
+      <keystroke key="shift-9" />
+      <check result="9:split_marker:OK" />
+    </test>
   </tests>
 </keyboardTest3>
diff --git a/core/tests/unit/ldml/keyboards/ldml_test.xml b/core/tests/unit/ldml/keyboards/ldml_test.xml
index 63bd4f1c08..17296a3c8a 100644
--- a/core/tests/unit/ldml/keyboards/ldml_test.xml
+++ b/core/tests/unit/ldml/keyboards/ldml_test.xml
@@ -13,6 +13,12 @@
     <key id="4" output="4:simple_reorder:UNTIED" />
     <key id="5" output="5:simple_vars:${varsok}"/>
     <key id="6" output="6:map_var:B\m{map1}X\m{map2}"/>
+    <key id="7" output="7:simple_uset:FAIL\m{uset7}" /> <!-- will produce OK-->
+    <key id="shift-7" output="7:simple_uset:OK\m{uset7}" /> <!-- will produce FAIL-->
+    <key id="8" output="\m{8ctxt}8:ctxt:FAIL" />
+    <key id="shift-8" output="𐒷" />
+    <key id="9" output="9:split_marker:FAIL\m{marker1}" />
+    <key id="shift-9" output="\m{marker2}" />
   </keys>
 
   <layers formId="us">
@@ -24,7 +30,7 @@
       <row keys="space"/>
     </layer>
     <layer modifiers="shift">
-      <row keys="tilde bang at hash dollar percent caret amp asterisk open-paren close-paren underscore plus"/>
+      <row keys="tilde bang at hash dollar percent caret shift-7 shift-8 shift-9 close-paren underscore plus"/>
       <row keys="Q W E R T Y U I O P open-curly close-curly pipe"/>
       <row keys="A S D F G H J K L colon double-quote"/>
       <row keys="Z X C V B N M open-angle close-angle question"/>
@@ -54,6 +60,9 @@
     <!-- 6: regular and rot13 alphabet -->
     <set id="alpha" value="$[alpha1] $[alpha2]"/>
     <set id="nycun" value="$[alpha2] $[alpha1]"/> <!-- 'nycun' in rot13 -->
+    <!-- 7: uset -->
+    <unicodeSet id="7ok" value="[[A_LIFE]-[E]]" /> <!-- = the chars [FAIL]-->
+    <unicodeSet id="7notok" value="[[A-Z]-$[7ok]]"/> <!-- everything not in [FAIL]-->
   </variables>
 
   <transforms type="simple">
@@ -98,16 +107,22 @@
     <!-- 6: swap back -->
     <transformGroup>
         <transform from="($[alpha])\m{map2}($[alpha])\m{map1}" to="$2\m{map1}$1\m{map2}" />
+        <transform from=":(?:$[7notok])+\m{uset7}" to=":FAIL" />
+        <transform from=":(?:$[7ok])+\m{uset7}" to=":OK" />
     </transformGroup>
     <transformGroup>
       <transform from="simple_transform:FAIL" to="simple_transform:OK" />
       <!-- 3: interpret marker results -->
       <transform from="FAIL\m{marker}" to="OK" />
+      <transform from="FAIL\m{marker1}\m{marker2}" to="OK" />
       <!-- 4: interpret reorder results -->
       <transform from="UNITED" to="OK" />
       <transform from="UNTIED" to="FAIL" />
       <!-- 6: if untransformed, BX is a failure. -->
       <transform from=":B\m{.}X\m{.}" to=":FAIL"/>
+      <transform from="ABC\m{8ctxt}(8:ctxt):FAIL" to="$1:OK" />
+      <transform from="𐓏\m{8ctxt}(8:ctxt):FAIL" to="$1:OK" />
+      <transform from="𐒻𐒷\m{8ctxt}(8:ctxt):FAIL" to="$1:OK" />
     </transformGroup>
   </transforms>