diff --git a/org.hl7.fhir.r4/src/main/java/org/hl7/fhir/r4/fhirpath/FHIRPathEngine.java b/org.hl7.fhir.r4/src/main/java/org/hl7/fhir/r4/fhirpath/FHIRPathEngine.java
index 3ca6de5b9..80920c0fa 100644
--- a/org.hl7.fhir.r4/src/main/java/org/hl7/fhir/r4/fhirpath/FHIRPathEngine.java
+++ b/org.hl7.fhir.r4/src/main/java/org/hl7/fhir/r4/fhirpath/FHIRPathEngine.java
@@ -4817,7 +4817,15 @@ public class FHIRPathEngine {
 
   private List<Base> funcToString(ExecutionContext context, List<Base> focus, ExpressionNode exp) {
     List<Base> result = new ArrayList<Base>();
-    result.add(new StringType(convertToString(focus)).noExtensions());
+    for (Base item : focus) {
+      String value = convertToString(item);
+      if (value != null)
+        result.add(new StringType(value).noExtensions());
+    }
+
+    if (result.size() > 1) {
+      throw makeException(exp, I18nConstants.FHIRPATH_NO_COLLECTION, "toString", result.size());
+    }
     return result;
   }
 
diff --git a/org.hl7.fhir.r4b/src/main/java/org/hl7/fhir/r4b/fhirpath/FHIRPathEngine.java b/org.hl7.fhir.r4b/src/main/java/org/hl7/fhir/r4b/fhirpath/FHIRPathEngine.java
index 60d32662d..eaf53f0d1 100644
--- a/org.hl7.fhir.r4b/src/main/java/org/hl7/fhir/r4b/fhirpath/FHIRPathEngine.java
+++ b/org.hl7.fhir.r4b/src/main/java/org/hl7/fhir/r4b/fhirpath/FHIRPathEngine.java
@@ -4820,7 +4820,15 @@ public class FHIRPathEngine {
 
   private List<Base> funcToString(ExecutionContext context, List<Base> focus, ExpressionNode exp) {
     List<Base> result = new ArrayList<Base>();
-    result.add(new StringType(convertToString(focus)).noExtensions());
+    for (Base item : focus) {
+      String value = convertToString(item);
+      if (value != null)
+        result.add(new StringType(value).noExtensions());
+    }
+
+    if (result.size() > 1) {
+      throw makeException(exp, I18nConstants.FHIRPATH_NO_COLLECTION, "toString", result.size());
+    }
     return result;
   }
 
diff --git a/org.hl7.fhir.r4b/src/test/java/org/hl7/fhir/r4b/test/FHIRPathTests.java b/org.hl7.fhir.r4b/src/test/java/org/hl7/fhir/r4b/test/FHIRPathTests.java
index 7a92e17b8..61b40c091 100644
--- a/org.hl7.fhir.r4b/src/test/java/org/hl7/fhir/r4b/test/FHIRPathTests.java
+++ b/org.hl7.fhir.r4b/src/test/java/org/hl7/fhir/r4b/test/FHIRPathTests.java
@@ -336,4 +336,23 @@ public class FHIRPathTests {
     assertEquals(1, results.size());
     assertEquals("123", results.get(0).toString());
   }
+
+  @Test
+  public void testEvaluate_ToStringOnDateValue() {
+    Patient input = new Patient();
+    var dtv = new DateType("2024");
+    input.setBirthDateElement(dtv);
+    List<Base> results = fp.evaluate(input, "Patient.birthDate.toString()");
+    assertEquals(1, results.size());
+    assertEquals("2024", results.get(0).toString());
+  }
+
+  @Test
+  public void testEvaluate_ToStringOnExtensionOnlyValue() {
+    Patient input = new Patient();
+    var dtv = new DateType();
+    input.setBirthDateElement(dtv);
+    List<Base> results = fp.evaluate(input, "Patient.birthDate.toString()");
+    assertEquals(0, results.size());
+  }
 }
\ No newline at end of file
diff --git a/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/fhirpath/FHIRPathEngine.java b/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/fhirpath/FHIRPathEngine.java
index 126ee57cc..c33917860 100644
--- a/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/fhirpath/FHIRPathEngine.java
+++ b/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/fhirpath/FHIRPathEngine.java
@@ -4929,7 +4929,15 @@ public class FHIRPathEngine {
 
   private List<Base> funcToString(ExecutionContext context, List<Base> focus, ExpressionNode exp) {
     List<Base> result = new ArrayList<Base>();
-    result.add(new StringType(convertToString(focus)).noExtensions());
+    for (Base item : focus) {
+      String value = convertToString(item);
+      if (value != null)
+        result.add(new StringType(value).noExtensions());
+    }
+
+    if (result.size() > 1) {
+      throw makeException(exp, I18nConstants.FHIRPATH_NO_COLLECTION, "toString", result.size());
+    }
     return result;
   }
 
diff --git a/org.hl7.fhir.r5/src/test/java/org/hl7/fhir/r5/test/FHIRPathTests.java b/org.hl7.fhir.r5/src/test/java/org/hl7/fhir/r5/test/FHIRPathTests.java
index 0bb10fd9d..e232cd803 100644
--- a/org.hl7.fhir.r5/src/test/java/org/hl7/fhir/r5/test/FHIRPathTests.java
+++ b/org.hl7.fhir.r5/src/test/java/org/hl7/fhir/r5/test/FHIRPathTests.java
@@ -1,340 +1,359 @@
-package org.hl7.fhir.r5.test;
-
-import java.io.FileNotFoundException;
-import java.io.IOException;
-import java.util.*;
-import java.util.stream.Stream;
-
-import javax.xml.parsers.ParserConfigurationException;
-
-import org.apache.commons.lang3.NotImplementedException;
-import org.fhir.ucum.UcumException;
-import org.hl7.fhir.exceptions.FHIRException;
-import org.hl7.fhir.exceptions.PathEngineException;
-import org.hl7.fhir.r5.context.SimpleWorkerContext;
-import org.hl7.fhir.r5.elementmodel.Manager;
-import org.hl7.fhir.r5.elementmodel.Manager.FhirFormat;
-import org.hl7.fhir.r5.fhirpath.ExpressionNode;
-import org.hl7.fhir.r5.fhirpath.FHIRPathEngine;
-import org.hl7.fhir.r5.fhirpath.TypeDetails;
-import org.hl7.fhir.r5.fhirpath.FHIRPathEngine.IEvaluationContext;
-import org.hl7.fhir.r5.fhirpath.FHIRPathUtilityClasses.FunctionDetails;
-import org.hl7.fhir.r5.elementmodel.ValidatedFragment;
-import org.hl7.fhir.r5.formats.JsonParser;
-import org.hl7.fhir.r5.formats.XmlParser;
-import org.hl7.fhir.r5.model.*;
-import org.hl7.fhir.r5.test.utils.TestingUtilities;
-import org.hl7.fhir.utilities.Utilities;
-import org.hl7.fhir.utilities.npm.FilesystemPackageCacheManager;
-import org.hl7.fhir.utilities.npm.NpmPackage;
-import org.hl7.fhir.utilities.xml.XMLUtil;
-import org.junit.jupiter.api.Assertions;
-import org.junit.jupiter.api.BeforeAll;
-import org.junit.jupiter.api.DisplayName;
-import org.junit.jupiter.api.Test;
-import org.junit.jupiter.params.ParameterizedTest;
-import org.junit.jupiter.params.provider.Arguments;
-import org.junit.jupiter.params.provider.MethodSource;
-import org.w3c.dom.Document;
-import org.w3c.dom.Element;
-import org.w3c.dom.Node;
-import org.xml.sax.SAXException;
-
-import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.mockito.Mockito.mock;
-
-public class FHIRPathTests {
-
-  public enum TestResultType {OK, SYNTAX, SEMANTICS, EXECUTION}
-
-  public class FHIRPathTestEvaluationServices implements IEvaluationContext {
-
-    @Override
-    public List<Base> resolveConstant(FHIRPathEngine engine, Object appContext, String name, boolean beforeContext, boolean explicitConstant) throws PathEngineException {
-      throw new NotImplementedException("Not done yet (FHIRPathTestEvaluationServices.resolveConstant), when item is element");
-    }
-
-    @Override
-    public TypeDetails resolveConstantType(FHIRPathEngine engine, Object appContext, String name, boolean explicitConstant) throws PathEngineException {
-      throw new NotImplementedException("Not done yet (FHIRPathTestEvaluationServices.resolveConstantType), when item is element");
-    }
-
-    @Override
-    public boolean log(String argument, List<Base> focus) {
-      return false;
-    }
-
-    @Override
-    public FunctionDetails resolveFunction(FHIRPathEngine engine, String functionName) {
-      throw new NotImplementedException("Not done yet (FHIRPathTestEvaluationServices.resolveFunction), when item is element (for " + functionName + ")");
-    }
-
-    @Override
-    public TypeDetails checkFunction(FHIRPathEngine engine, Object appContext, String functionName, TypeDetails focus, List<TypeDetails> parameters) throws PathEngineException {
-      throw new NotImplementedException("Not done yet (FHIRPathTestEvaluationServices.checkFunction), when item is element");
-    }
-
-    @Override
-    public List<Base> executeFunction(FHIRPathEngine engine, Object appContext, List<Base> focus, String functionName, List<List<Base>> parameters) {
-      throw new NotImplementedException("Not done yet (FHIRPathTestEvaluationServices.executeFunction), when item is element");
-    }
-
-    @Override
-    public Base resolveReference(FHIRPathEngine engine, Object appContext, String url, Base refContext) throws FHIRException {
-      throw new NotImplementedException("Not done yet (FHIRPathTestEvaluationServices.resolveReference), when item is element");
-    }
-
-    @Override
-    public boolean conformsToProfile(FHIRPathEngine engine, Object appContext, Base item, String url) throws FHIRException {
-      if (url.equals("http://hl7.org/fhir/StructureDefinition/Patient"))
-        return true;
-      if (url.equals("http://hl7.org/fhir/StructureDefinition/Person"))
-        return false;
-      throw new FHIRException("unknown profile " + url);
-
-    }
-
-    @Override
-    public ValueSet resolveValueSet(FHIRPathEngine engine, Object appContext, String url) {
-      return context.fetchResource(ValueSet.class, url);
-    }
-
-    @Override
-    public boolean paramIsType(String name, int index) {
-      return false;
-    }
-  }
-
-  private static FHIRPathEngine fp;
-  private final Map<String, Base> resources = new HashMap<String, Base>();
-  private static SimpleWorkerContext context;
-
-  @BeforeAll
-  public static void setUp() throws FileNotFoundException, FHIRException, IOException {
-    context = new SimpleWorkerContext((SimpleWorkerContext) TestingUtilities.getSharedWorkerContext());
-    if (!context.hasPackage("hl7.cda.us.ccda", null)) {
-      FilesystemPackageCacheManager pcm = new FilesystemPackageCacheManager.Builder().build();
-      NpmPackage npm = pcm.loadPackage("hl7.cda.uv.core", "2.0.0");
-      context.loadFromPackage(npm, null);
-      npm = pcm.loadPackage("hl7.cda.us.ccda", "current");
-      context.loadFromPackage(npm, null);
-    }
-    if (fp == null) {
-      fp = new FHIRPathEngine(context);
-    }
-  }
-
-  public static Stream<Arguments> data() throws ParserConfigurationException, SAXException, IOException {
-    Document dom = XMLUtil.parseToDom(TestingUtilities.loadTestResource("r5", "fhirpath", "tests-fhir-r5.xml"));
-
-    List<Element> list = new ArrayList<Element>();
-    List<Element> groups = new ArrayList<Element>();
-    XMLUtil.getNamedChildren(dom.getDocumentElement(), "group", groups);
-    for (Element g : groups) {
-      XMLUtil.getNamedChildren(g, "test", list);
-      XMLUtil.getNamedChildren(g, "modeTest", list);
-    }
-
-    List<Arguments> objects = new ArrayList<>();
-    for (Element e : list) {
-      objects.add(Arguments.of(getName(e), e));
-    }
-
-    return objects.stream();
-  }
-
-  private static Object getName(Element e) {
-    String s = e.getAttribute("name");
-    Element p = (Element) e.getParentNode();
-    int ndx = 0;
-    for (int i = 0; i < p.getChildNodes().getLength(); i++) {
-      Node c = p.getChildNodes().item(i);
-      if (c == e) {
-        break;
-      } else if (c instanceof Element) {
-        ndx++;
-      }
-    }
-    if (Utilities.noString(s)) {
-      s = "?? - G " + p.getAttribute("name") + "[" + Integer.toString(ndx + 1) + "]";
-    } else {
-      s = s + " - G " + p.getAttribute("name") + "[" + Integer.toString(ndx + 1) + "]";
-    }
-    return s;
-  }
-
-  @SuppressWarnings("deprecation")
-  @ParameterizedTest(name = "{index}: file {0}")
-  @MethodSource("data")
-  public void test(String name, Element test) throws FileNotFoundException, IOException, FHIRException, org.hl7.fhir.exceptions.FHIRException, UcumException {
-    // Setting timezone for this test. Grahame is in UTC+11, Travis is in GMT, and I'm here in Toronto, Canada with
-    // all my time based tests failing locally...
-    TimeZone.setDefault(TimeZone.getTimeZone("UTC+1100"));
-
-    fp.setHostServices(new FHIRPathTestEvaluationServices());
-    String input = test.getAttribute("inputfile");
-    String expression = XMLUtil.getNamedChild(test, "expression").getTextContent();
-    TestResultType fail = TestResultType.OK;
-    if ("syntax".equals(XMLUtil.getNamedChild(test, "expression").getAttribute("invalid"))) {
-      fail = TestResultType.SYNTAX;
-    } else if ("semantic".equals(XMLUtil.getNamedChild(test, "expression").getAttribute("invalid"))) {
-      fail = TestResultType.SEMANTICS;      
-    } else if ("execution".equals(XMLUtil.getNamedChild(test, "expression").getAttribute("invalid"))) {
-      fail = TestResultType.EXECUTION;      
-    };
-    fp.setAllowPolymorphicNames("lenient/polymorphics".equals(test.getAttribute("mode")));
-    boolean skipStaticCheck = false;
-    if ("true".equals(test.getAttribute("skipStaticCheck")))
-      skipStaticCheck = true;
-    Base res = null;
-
-    List<Base> outcome = new ArrayList<Base>();
-
-    System.out.println(name);
-
-    ExpressionNode node = null;
-    try {
-      node = fp.parse(expression);
-      Assertions.assertTrue(fail != TestResultType.SYNTAX, String.format("Expected exception didn't occur parsing %s", expression));
-    } catch (Exception e) {
-      System.out.println("Parsing Error: "+e.getMessage());
-      Assertions.assertTrue(fail == TestResultType.SYNTAX, String.format("Unexpected exception parsing %s: " + e.getMessage(), expression));
-    }
-    
-    if (node != null) {
-      if (!Utilities.noString(input)) {
-        res = resources.get(input);
-        if (res == null) {
-          if ("cda".equals(test.getAttribute("mode"))) {
-            res = Manager.makeParser(fp.getWorker(), FhirFormat.XML).parseSingle(TestingUtilities.loadTestResourceStream("r5", input), null);            
-          } else if (input.endsWith(".json")) {
-            res = new JsonParser().parse(TestingUtilities.loadTestResourceStream("r5", input));              
-          } else {
-            res = new XmlParser().parse(TestingUtilities.loadTestResourceStream("r5", input));
-          }
-          resources.put(input, res);
-        }        
-      }
-      
-      if (!skipStaticCheck) {
-        try {
-          if (Utilities.noString(input)) {
-            fp.check(null, null, node);
-          } else {
-            fp.check(res, res.fhirType(), res.fhirType(), node);
-          }
-          Assertions.assertTrue(fail != TestResultType.SEMANTICS, String.format("Expected exception didn't occur checking %s", expression));
-        } catch (Exception e) {
-          System.out.println("Checking Error: "+e.getMessage());
-          Assertions.assertTrue(fail == TestResultType.SEMANTICS, String.format("Unexpected exception checking %s: " + e.getMessage(), expression));
-          node = null;
-        }
-      }
-    }
-    
-    if (node != null) {
-      try {
-        if ("element".equals(test.getAttribute("mode"))) {
-          List<ValidatedFragment> e = Manager.parse(fp.getWorker(), TestingUtilities.loadTestResourceStream("r5", input), input.endsWith(".json") ? FhirFormat.JSON : FhirFormat.XML);                        
-          outcome = fp.evaluate(e.get(0).getElement(), node);
-        } else {
-          outcome = fp.evaluate(res, node);
-        }
-        Assertions.assertTrue(fail == TestResultType.OK, String.format("Expected exception didn't occur executing %s", expression));
-      } catch (Exception e) {
-        System.out.println("Execution Error: "+e.getMessage());
-        Assertions.assertTrue(fail == TestResultType.EXECUTION, String.format("Unexpected exception executing %s: " + e.getMessage(), expression));
-        node = null;
-      }
-    }
-
-    if (fp.hasLog()) {
-      System.out.println(name);
-      System.out.println(fp.takeLog());
-    }
-
-    if (node != null) {
-      if ("true".equals(test.getAttribute("predicate"))) {
-        boolean ok = fp.convertToBoolean(outcome);
-        outcome.clear();
-        outcome.add(new BooleanType(ok));
-      }
-
-      List<Element> expected = new ArrayList<Element>();
-      XMLUtil.getNamedChildren(test, "output", expected);
-      assertEquals(outcome.size(), expected.size(), String.format("Expected %d objects but found %d for expression %s", expected.size(), outcome.size(), expression));
-      if ("false".equals(test.getAttribute("ordered"))) {
-        for (int i = 0; i < Math.min(outcome.size(), expected.size()); i++) {
-          String tn = outcome.get(i).fhirType();
-          String s;
-          if (outcome.get(i) instanceof Quantity) {
-            s = fp.convertToString(outcome.get(i));
-          } else {
-            s = ((PrimitiveType) outcome.get(i)).asStringValue();
-          }
-          boolean found = false;
-          for (Element e : expected) {
-            if ((Utilities.noString(e.getAttribute("type")) || e.getAttribute("type").equals(tn)) &&
-                (Utilities.noString(e.getTextContent()) || e.getTextContent().equals(s))) {
-              found = true;
-            }
-          }
-          Assertions.assertTrue(found, String.format("Outcome %d: Value %s of type %s not expected for %s", i, s, tn, expression));
-        }
-      } else {
-        for (int i = 0; i < Math.min(outcome.size(), expected.size()); i++) {
-          String tn = expected.get(i).getAttribute("type");
-          if (!Utilities.noString(tn)) {
-            assertEquals(tn, outcome.get(i).fhirType(), String.format("Outcome %d: Type should be %s but was %s", i, tn, outcome.get(i).fhirType()));
-          }
-          String v = expected.get(i).getTextContent();
-          if (!Utilities.noString(v)) {
-            if (outcome.get(i) instanceof Quantity) {
-              Quantity q = fp.parseQuantityString(v);
-              Assertions.assertTrue(outcome.get(i).equalsDeep(q), String.format("Outcome %d: Value should be %s but was %s", i, v, outcome.get(i).toString()));
-            } else {
-              Assertions.assertTrue(outcome.get(i) instanceof PrimitiveType, String.format("Outcome %d: Value should be a primitive type but was %s", i, outcome.get(i).fhirType()));
-              if (!(v.equals(((PrimitiveType) outcome.get(i)).fpValue()))) {
-                System.out.println(name);
-                System.out.println(String.format("Outcome %d: Value should be %s but was %s for expression %s", i, v, ((PrimitiveType) outcome.get(i)).fpValue(), expression));
-              }
-              assertEquals(v, ((PrimitiveType) outcome.get(i)).fpValue(), String.format("Outcome %d: Value should be %s but was %s for expression %s", i, v, ((PrimitiveType) outcome.get(i)).fpValue(), expression));
-            }
-          }
-        }
-      }
-    }
-  }
-
-  @Test
-  @DisplayName("resolveConstant returns a list of Base")
-  public void resolveConstantReturnsList() {
-    final String DUMMY_CONSTANT_1 = "dummyConstant1";
-    final String DUMMY_CONSTANT_2 = "dummyConstant2";
-    fp.setHostServices(new FHIRPathTestEvaluationServices() {
-      @Override
-      public List<Base> resolveConstant(FHIRPathEngine engine, Object appContext, String name, boolean beforeContext, boolean explicitConstant) throws PathEngineException {
-
-        return Arrays.asList(
-          new StringType(DUMMY_CONSTANT_1).noExtensions(),
-          new StringType(DUMMY_CONSTANT_2).noExtensions());
-      }
-    });
-
-    ExpressionNode expressionNode = fp.parse("%dummyConstant");
-
-    List<Base> result = fp.evaluate(null, expressionNode);
-    assertEquals(2, result.size());
-    assertEquals(DUMMY_CONSTANT_1, result.get(0).primitiveValue());
-    assertEquals(DUMMY_CONSTANT_2, result.get(1).primitiveValue());
-  }
-
-  @Test
-  public void testEvaluate_Id() {
-    Patient input = new Patient();
-    input.setId(new IdType("http://base/Patient/123/_history/222"));
-    List<Base> results = fp.evaluate(input, "Patient.id");
-    assertEquals(1, results.size());
-    assertEquals("123", results.get(0).toString());
-  }
+package org.hl7.fhir.r5.test;
+
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.util.*;
+import java.util.stream.Stream;
+
+import javax.xml.parsers.ParserConfigurationException;
+
+import org.apache.commons.lang3.NotImplementedException;
+import org.fhir.ucum.UcumException;
+import org.hl7.fhir.exceptions.FHIRException;
+import org.hl7.fhir.exceptions.PathEngineException;
+import org.hl7.fhir.r5.context.SimpleWorkerContext;
+import org.hl7.fhir.r5.elementmodel.Manager;
+import org.hl7.fhir.r5.elementmodel.Manager.FhirFormat;
+import org.hl7.fhir.r5.fhirpath.ExpressionNode;
+import org.hl7.fhir.r5.fhirpath.FHIRPathEngine;
+import org.hl7.fhir.r5.fhirpath.TypeDetails;
+import org.hl7.fhir.r5.fhirpath.FHIRPathEngine.IEvaluationContext;
+import org.hl7.fhir.r5.fhirpath.FHIRPathUtilityClasses.FunctionDetails;
+import org.hl7.fhir.r5.elementmodel.ValidatedFragment;
+import org.hl7.fhir.r5.formats.JsonParser;
+import org.hl7.fhir.r5.formats.XmlParser;
+import org.hl7.fhir.r5.model.*;
+import org.hl7.fhir.r5.test.utils.TestingUtilities;
+import org.hl7.fhir.utilities.Utilities;
+import org.hl7.fhir.utilities.npm.FilesystemPackageCacheManager;
+import org.hl7.fhir.utilities.npm.NpmPackage;
+import org.hl7.fhir.utilities.xml.XMLUtil;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+import org.w3c.dom.Document;
+import org.w3c.dom.Element;
+import org.w3c.dom.Node;
+import org.xml.sax.SAXException;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.mockito.Mockito.mock;
+
+public class FHIRPathTests {
+
+  public enum TestResultType {OK, SYNTAX, SEMANTICS, EXECUTION}
+
+  public class FHIRPathTestEvaluationServices implements IEvaluationContext {
+
+    @Override
+    public List<Base> resolveConstant(FHIRPathEngine engine, Object appContext, String name, boolean beforeContext, boolean explicitConstant) throws PathEngineException {
+      throw new NotImplementedException("Not done yet (FHIRPathTestEvaluationServices.resolveConstant), when item is element");
+    }
+
+    @Override
+    public TypeDetails resolveConstantType(FHIRPathEngine engine, Object appContext, String name, boolean explicitConstant) throws PathEngineException {
+      throw new NotImplementedException("Not done yet (FHIRPathTestEvaluationServices.resolveConstantType), when item is element");
+    }
+
+    @Override
+    public boolean log(String argument, List<Base> focus) {
+      return false;
+    }
+
+    @Override
+    public FunctionDetails resolveFunction(FHIRPathEngine engine, String functionName) {
+      throw new NotImplementedException("Not done yet (FHIRPathTestEvaluationServices.resolveFunction), when item is element (for " + functionName + ")");
+    }
+
+    @Override
+    public TypeDetails checkFunction(FHIRPathEngine engine, Object appContext, String functionName, TypeDetails focus, List<TypeDetails> parameters) throws PathEngineException {
+      throw new NotImplementedException("Not done yet (FHIRPathTestEvaluationServices.checkFunction), when item is element");
+    }
+
+    @Override
+    public List<Base> executeFunction(FHIRPathEngine engine, Object appContext, List<Base> focus, String functionName, List<List<Base>> parameters) {
+      throw new NotImplementedException("Not done yet (FHIRPathTestEvaluationServices.executeFunction), when item is element");
+    }
+
+    @Override
+    public Base resolveReference(FHIRPathEngine engine, Object appContext, String url, Base refContext) throws FHIRException {
+      throw new NotImplementedException("Not done yet (FHIRPathTestEvaluationServices.resolveReference), when item is element");
+    }
+
+    @Override
+    public boolean conformsToProfile(FHIRPathEngine engine, Object appContext, Base item, String url) throws FHIRException {
+      if (url.equals("http://hl7.org/fhir/StructureDefinition/Patient"))
+        return true;
+      if (url.equals("http://hl7.org/fhir/StructureDefinition/Person"))
+        return false;
+      throw new FHIRException("unknown profile " + url);
+
+    }
+
+    @Override
+    public ValueSet resolveValueSet(FHIRPathEngine engine, Object appContext, String url) {
+      return context.fetchResource(ValueSet.class, url);
+    }
+
+    @Override
+    public boolean paramIsType(String name, int index) {
+      return false;
+    }
+  }
+
+  private static FHIRPathEngine fp;
+  private final Map<String, Base> resources = new HashMap<String, Base>();
+  private static SimpleWorkerContext context;
+
+  @BeforeAll
+  public static void setUp() throws FileNotFoundException, FHIRException, IOException {
+    context = new SimpleWorkerContext((SimpleWorkerContext) TestingUtilities.getSharedWorkerContext());
+    if (!context.hasPackage("hl7.cda.us.ccda", null)) {
+      FilesystemPackageCacheManager pcm = new FilesystemPackageCacheManager.Builder().build();
+      NpmPackage npm = pcm.loadPackage("hl7.cda.uv.core", "2.0.0");
+      context.loadFromPackage(npm, null);
+      npm = pcm.loadPackage("hl7.cda.us.ccda", "current");
+      context.loadFromPackage(npm, null);
+    }
+    if (fp == null) {
+      fp = new FHIRPathEngine(context);
+    }
+  }
+
+  public static Stream<Arguments> data() throws ParserConfigurationException, SAXException, IOException {
+    Document dom = XMLUtil.parseToDom(TestingUtilities.loadTestResource("r5", "fhirpath", "tests-fhir-r5.xml"));
+
+    List<Element> list = new ArrayList<Element>();
+    List<Element> groups = new ArrayList<Element>();
+    XMLUtil.getNamedChildren(dom.getDocumentElement(), "group", groups);
+    for (Element g : groups) {
+      XMLUtil.getNamedChildren(g, "test", list);
+      XMLUtil.getNamedChildren(g, "modeTest", list);
+    }
+
+    List<Arguments> objects = new ArrayList<>();
+    for (Element e : list) {
+      objects.add(Arguments.of(getName(e), e));
+    }
+
+    return objects.stream();
+  }
+
+  private static Object getName(Element e) {
+    String s = e.getAttribute("name");
+    Element p = (Element) e.getParentNode();
+    int ndx = 0;
+    for (int i = 0; i < p.getChildNodes().getLength(); i++) {
+      Node c = p.getChildNodes().item(i);
+      if (c == e) {
+        break;
+      } else if (c instanceof Element) {
+        ndx++;
+      }
+    }
+    if (Utilities.noString(s)) {
+      s = "?? - G " + p.getAttribute("name") + "[" + Integer.toString(ndx + 1) + "]";
+    } else {
+      s = s + " - G " + p.getAttribute("name") + "[" + Integer.toString(ndx + 1) + "]";
+    }
+    return s;
+  }
+
+  @SuppressWarnings("deprecation")
+  @ParameterizedTest(name = "{index}: file {0}")
+  @MethodSource("data")
+  public void test(String name, Element test) throws FileNotFoundException, IOException, FHIRException, org.hl7.fhir.exceptions.FHIRException, UcumException {
+    // Setting timezone for this test. Grahame is in UTC+11, Travis is in GMT, and I'm here in Toronto, Canada with
+    // all my time based tests failing locally...
+    TimeZone.setDefault(TimeZone.getTimeZone("UTC+1100"));
+
+    fp.setHostServices(new FHIRPathTestEvaluationServices());
+    String input = test.getAttribute("inputfile");
+    String expression = XMLUtil.getNamedChild(test, "expression").getTextContent();
+    TestResultType fail = TestResultType.OK;
+    if ("syntax".equals(XMLUtil.getNamedChild(test, "expression").getAttribute("invalid"))) {
+      fail = TestResultType.SYNTAX;
+    } else if ("semantic".equals(XMLUtil.getNamedChild(test, "expression").getAttribute("invalid"))) {
+      fail = TestResultType.SEMANTICS;      
+    } else if ("execution".equals(XMLUtil.getNamedChild(test, "expression").getAttribute("invalid"))) {
+      fail = TestResultType.EXECUTION;      
+    };
+    fp.setAllowPolymorphicNames("lenient/polymorphics".equals(test.getAttribute("mode")));
+    boolean skipStaticCheck = false;
+    if ("true".equals(test.getAttribute("skipStaticCheck")))
+      skipStaticCheck = true;
+    Base res = null;
+
+    List<Base> outcome = new ArrayList<Base>();
+
+    System.out.println(name);
+
+    ExpressionNode node = null;
+    try {
+      node = fp.parse(expression);
+      Assertions.assertTrue(fail != TestResultType.SYNTAX, String.format("Expected exception didn't occur parsing %s", expression));
+    } catch (Exception e) {
+      System.out.println("Parsing Error: "+e.getMessage());
+      Assertions.assertTrue(fail == TestResultType.SYNTAX, String.format("Unexpected exception parsing %s: " + e.getMessage(), expression));
+    }
+    
+    if (node != null) {
+      if (!Utilities.noString(input)) {
+        res = resources.get(input);
+        if (res == null) {
+          if ("cda".equals(test.getAttribute("mode"))) {
+            res = Manager.makeParser(fp.getWorker(), FhirFormat.XML).parseSingle(TestingUtilities.loadTestResourceStream("r5", input), null);            
+          } else if (input.endsWith(".json")) {
+            res = new JsonParser().parse(TestingUtilities.loadTestResourceStream("r5", input));              
+          } else {
+            res = new XmlParser().parse(TestingUtilities.loadTestResourceStream("r5", input));
+          }
+          resources.put(input, res);
+        }        
+      }
+      
+      if (!skipStaticCheck) {
+        try {
+          if (Utilities.noString(input)) {
+            fp.check(null, null, node);
+          } else {
+            fp.check(res, res.fhirType(), res.fhirType(), node);
+          }
+          Assertions.assertTrue(fail != TestResultType.SEMANTICS, String.format("Expected exception didn't occur checking %s", expression));
+        } catch (Exception e) {
+          System.out.println("Checking Error: "+e.getMessage());
+          Assertions.assertTrue(fail == TestResultType.SEMANTICS, String.format("Unexpected exception checking %s: " + e.getMessage(), expression));
+          node = null;
+        }
+      }
+    }
+    
+    if (node != null) {
+      try {
+        if ("element".equals(test.getAttribute("mode"))) {
+          List<ValidatedFragment> e = Manager.parse(fp.getWorker(), TestingUtilities.loadTestResourceStream("r5", input), input.endsWith(".json") ? FhirFormat.JSON : FhirFormat.XML);                        
+          outcome = fp.evaluate(e.get(0).getElement(), node);
+        } else {
+          outcome = fp.evaluate(res, node);
+        }
+        Assertions.assertTrue(fail == TestResultType.OK, String.format("Expected exception didn't occur executing %s", expression));
+      } catch (Exception e) {
+        System.out.println("Execution Error: "+e.getMessage());
+        Assertions.assertTrue(fail == TestResultType.EXECUTION, String.format("Unexpected exception executing %s: " + e.getMessage(), expression));
+        node = null;
+      }
+    }
+
+    if (fp.hasLog()) {
+      System.out.println(name);
+      System.out.println(fp.takeLog());
+    }
+
+    if (node != null) {
+      if ("true".equals(test.getAttribute("predicate"))) {
+        boolean ok = fp.convertToBoolean(outcome);
+        outcome.clear();
+        outcome.add(new BooleanType(ok));
+      }
+
+      List<Element> expected = new ArrayList<Element>();
+      XMLUtil.getNamedChildren(test, "output", expected);
+      assertEquals(outcome.size(), expected.size(), String.format("Expected %d objects but found %d for expression %s", expected.size(), outcome.size(), expression));
+      if ("false".equals(test.getAttribute("ordered"))) {
+        for (int i = 0; i < Math.min(outcome.size(), expected.size()); i++) {
+          String tn = outcome.get(i).fhirType();
+          String s;
+          if (outcome.get(i) instanceof Quantity) {
+            s = fp.convertToString(outcome.get(i));
+          } else {
+            s = ((PrimitiveType) outcome.get(i)).asStringValue();
+          }
+          boolean found = false;
+          for (Element e : expected) {
+            if ((Utilities.noString(e.getAttribute("type")) || e.getAttribute("type").equals(tn)) &&
+                (Utilities.noString(e.getTextContent()) || e.getTextContent().equals(s))) {
+              found = true;
+            }
+          }
+          Assertions.assertTrue(found, String.format("Outcome %d: Value %s of type %s not expected for %s", i, s, tn, expression));
+        }
+      } else {
+        for (int i = 0; i < Math.min(outcome.size(), expected.size()); i++) {
+          String tn = expected.get(i).getAttribute("type");
+          if (!Utilities.noString(tn)) {
+            assertEquals(tn, outcome.get(i).fhirType(), String.format("Outcome %d: Type should be %s but was %s", i, tn, outcome.get(i).fhirType()));
+          }
+          String v = expected.get(i).getTextContent();
+          if (!Utilities.noString(v)) {
+            if (outcome.get(i) instanceof Quantity) {
+              Quantity q = fp.parseQuantityString(v);
+              Assertions.assertTrue(outcome.get(i).equalsDeep(q), String.format("Outcome %d: Value should be %s but was %s", i, v, outcome.get(i).toString()));
+            } else {
+              Assertions.assertTrue(outcome.get(i) instanceof PrimitiveType, String.format("Outcome %d: Value should be a primitive type but was %s", i, outcome.get(i).fhirType()));
+              if (!(v.equals(((PrimitiveType) outcome.get(i)).fpValue()))) {
+                System.out.println(name);
+                System.out.println(String.format("Outcome %d: Value should be %s but was %s for expression %s", i, v, ((PrimitiveType) outcome.get(i)).fpValue(), expression));
+              }
+              assertEquals(v, ((PrimitiveType) outcome.get(i)).fpValue(), String.format("Outcome %d: Value should be %s but was %s for expression %s", i, v, ((PrimitiveType) outcome.get(i)).fpValue(), expression));
+            }
+          }
+        }
+      }
+    }
+  }
+
+  @Test
+  @DisplayName("resolveConstant returns a list of Base")
+  public void resolveConstantReturnsList() {
+    final String DUMMY_CONSTANT_1 = "dummyConstant1";
+    final String DUMMY_CONSTANT_2 = "dummyConstant2";
+    fp.setHostServices(new FHIRPathTestEvaluationServices() {
+      @Override
+      public List<Base> resolveConstant(FHIRPathEngine engine, Object appContext, String name, boolean beforeContext, boolean explicitConstant) throws PathEngineException {
+
+        return Arrays.asList(
+          new StringType(DUMMY_CONSTANT_1).noExtensions(),
+          new StringType(DUMMY_CONSTANT_2).noExtensions());
+      }
+    });
+
+    ExpressionNode expressionNode = fp.parse("%dummyConstant");
+
+    List<Base> result = fp.evaluate(null, expressionNode);
+    assertEquals(2, result.size());
+    assertEquals(DUMMY_CONSTANT_1, result.get(0).primitiveValue());
+    assertEquals(DUMMY_CONSTANT_2, result.get(1).primitiveValue());
+  }
+
+  @Test
+  public void testEvaluate_Id() {
+    Patient input = new Patient();
+    input.setId(new IdType("http://base/Patient/123/_history/222"));
+    List<Base> results = fp.evaluate(input, "Patient.id");
+    assertEquals(1, results.size());
+    assertEquals("123", results.get(0).toString());
+  }
+
+  @Test
+  public void testEvaluate_ToStringOnDateValue() {
+    Patient input = new Patient();
+    var dtv = new DateType("2024");
+    input.setBirthDateElement(dtv);
+    List<Base> results = fp.evaluate(input, "Patient.birthDate.toString()");
+    assertEquals(1, results.size());
+    assertEquals("2024", results.get(0).toString());
+  }
+
+  @Test
+  public void testEvaluate_ToStringOnExtensionOnlyValue() {
+    Patient input = new Patient();
+    var dtv = new DateType();
+    input.setBirthDateElement(dtv);
+    List<Base> results = fp.evaluate(input, "Patient.birthDate.toString()");
+    assertEquals(0, results.size());
+  }
 }
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