diff --git a/hapi-fhir-base/src/main/java/ca/uhn/fhir/util/ParametersUtil.java b/hapi-fhir-base/src/main/java/ca/uhn/fhir/util/ParametersUtil.java
index 0d00118bb0d..a82efced19e 100644
--- a/hapi-fhir-base/src/main/java/ca/uhn/fhir/util/ParametersUtil.java
+++ b/hapi-fhir-base/src/main/java/ca/uhn/fhir/util/ParametersUtil.java
@@ -129,6 +129,15 @@ public class ParametersUtil {
 		return getParameterPartValue(theCtx, theParameter, theParameterName).map(t -> (IPrimitiveType<?>) t).map(t -> t.getValueAsString()).orElse(null);
 	}
 
+	public static Optional<Integer> getParameterPartValueAsInteger(FhirContext theCtx, IBase theParameter, String theParameterName) {
+		return getParameterPartValue(theCtx, theParameter, theParameterName)
+			.filter(t -> IPrimitiveType.class.isAssignableFrom(t.getClass()))
+			.map(t -> (IPrimitiveType<?>) t)
+			.map(IPrimitiveType::getValue)
+			.filter(t -> Integer.class.isAssignableFrom(t.getClass()))
+			.map(t -> (Integer) t);
+	}
+
 	private static <T> List<T> extractNamedParameters(FhirContext theCtx, IBaseParameters theParameters, String theParameterName, Function<IPrimitiveType<?>, T> theMapper) {
 		List<T> retVal = new ArrayList<>();
 
diff --git a/hapi-fhir-jpaserver-test-r4/pom.xml b/hapi-fhir-jpaserver-test-r4/pom.xml
index 5dbd847ba96..aaa9d8b1a1f 100644
--- a/hapi-fhir-jpaserver-test-r4/pom.xml
+++ b/hapi-fhir-jpaserver-test-r4/pom.xml
@@ -45,6 +45,16 @@
 			</exclusions>
 			<scope>test</scope>
 		</dependency>
+		<dependency>
+			<groupId>org.xmlunit</groupId>
+			<artifactId>xmlunit-core</artifactId>
+			<scope>test</scope>
+		</dependency>
+		<dependency>
+			<groupId>javax.json</groupId>
+			<artifactId>javax.json-api</artifactId>
+			<scope>test</scope>
+		</dependency>
     </dependencies>
 
 	<build>
diff --git a/hapi-fhir-jpaserver-test-r4/src/test/java/ca/uhn/fhir/jpa/patch/FhirPatchApplyR4Test.java b/hapi-fhir-jpaserver-test-r4/src/test/java/ca/uhn/fhir/jpa/patch/FhirPatchApplyR4Test.java
index 7e7f9e9cfe5..87eb166506f 100644
--- a/hapi-fhir-jpaserver-test-r4/src/test/java/ca/uhn/fhir/jpa/patch/FhirPatchApplyR4Test.java
+++ b/hapi-fhir-jpaserver-test-r4/src/test/java/ca/uhn/fhir/jpa/patch/FhirPatchApplyR4Test.java
@@ -1,7 +1,9 @@
 package ca.uhn.fhir.jpa.patch;
 
 import ca.uhn.fhir.context.FhirContext;
+import ca.uhn.fhir.context.FhirVersionEnum;
 import ca.uhn.fhir.i18n.Msg;
+import ca.uhn.fhir.parser.IParser;
 import ca.uhn.fhir.rest.server.exceptions.InvalidRequestException;
 import org.hl7.fhir.instance.model.api.IBase;
 import org.hl7.fhir.instance.model.api.IBaseResource;
@@ -21,8 +23,11 @@ import org.hl7.fhir.r4.model.StringType;
 import org.hl7.fhir.r4.model.Type;
 import org.hl7.fhir.r4.model.UriType;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
+import org.springframework.test.util.XmlExpectationsHelper;
 
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
@@ -33,6 +38,7 @@ import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.hasSize;
 import static org.hamcrest.Matchers.is;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
 public class FhirPatchApplyR4Test {
 
@@ -89,6 +95,35 @@ public class FhirPatchApplyR4Test {
 		}
 	}
 
+	@Test
+	public void testInsertToInvalidIndex_minimum() {
+		FhirPatch svc = new FhirPatch(ourCtx);
+
+		Patient patient = new Patient();
+
+		Parameters patch = new Parameters();
+		Parameters.ParametersParameterComponent operation = patch.addParameter();
+		operation.setName("operation");
+		operation
+			.addPart()
+			.setName("type")
+			.setValue(new CodeType("insert"));
+		operation
+			.addPart()
+			.setName("path")
+			.setValue(new StringType("Patient.identifier"));
+		operation
+			.addPart()
+			.setName("index")
+			.setValue(new IntegerType(-1));
+
+		try {
+			svc.apply(patient, patch);
+		} catch (InvalidRequestException e) {
+			assertEquals(Msg.code(1270) + "Invalid insert index -1 for path Patient.identifier - Only have 0 existing entries", e.getMessage());
+		}
+	}
+
 	@Test
 	public void testMoveFromInvalidIndex() {
 		FhirPatch svc = new FhirPatch(ourCtx);
@@ -122,6 +157,39 @@ public class FhirPatchApplyR4Test {
 		}
 	}
 
+	@Test
+	public void testMoveFromInvalidIndex_minimum() {
+		FhirPatch svc = new FhirPatch(ourCtx);
+
+		Patient patient = new Patient();
+
+		Parameters patch = new Parameters();
+		Parameters.ParametersParameterComponent operation = patch.addParameter();
+		operation.setName("operation");
+		operation
+			.addPart()
+			.setName("type")
+			.setValue(new CodeType("move"));
+		operation
+			.addPart()
+			.setName("path")
+			.setValue(new StringType("Patient.identifier"));
+		operation
+			.addPart()
+			.setName("source")
+			.setValue(new IntegerType(-1));
+		operation
+			.addPart()
+			.setName("destination")
+			.setValue(new IntegerType(1));
+
+		try {
+			svc.apply(patient, patch);
+		} catch (InvalidRequestException e) {
+			assertEquals(Msg.code(1268) + "Invalid move source index -1 for path Patient.identifier - Only have 0 existing entries", e.getMessage());
+		}
+	}
+
 	@Test
 	public void testMoveToInvalidIndex() {
 		FhirPatch svc = new FhirPatch(ourCtx);
@@ -156,6 +224,40 @@ public class FhirPatchApplyR4Test {
 		}
 	}
 
+	@Test
+	public void testMoveToInvalidIndex_minimum() {
+		FhirPatch svc = new FhirPatch(ourCtx);
+
+		Patient patient = new Patient();
+		patient.addIdentifier().setSystem("sys");
+
+		Parameters patch = new Parameters();
+		Parameters.ParametersParameterComponent operation = patch.addParameter();
+		operation.setName("operation");
+		operation
+			.addPart()
+			.setName("type")
+			.setValue(new CodeType("move"));
+		operation
+			.addPart()
+			.setName("path")
+			.setValue(new StringType("Patient.identifier"));
+		operation
+			.addPart()
+			.setName("source")
+			.setValue(new IntegerType(0));
+		operation
+			.addPart()
+			.setName("destination")
+			.setValue(new IntegerType(-1));
+
+		try {
+			svc.apply(patient, patch);
+		} catch (InvalidRequestException e) {
+			assertEquals(Msg.code(1269) + "Invalid move destination index -1 for path Patient.identifier - Only have 0 existing entries", e.getMessage());
+		}
+	}
+
 	@Test
 	public void testDeleteItemWithExtension() {
 		FhirPatch svc = new FhirPatch(ourCtx);
@@ -496,4 +598,49 @@ public class FhirPatchApplyR4Test {
 		}
 	}
 
+	// This implements the official HL7 test suite, as defined in http://hl7.org/fhir/R4/test-cases.zip. There may be some overlap with the cases above.
+	@ParameterizedTest
+	@CsvSource(textBlock = """
+		No Difference, <Patient xmlns="http://hl7.org/fhir"><birthDate value="1920-01-01"/></Patient>, <Parameters xmlns="http://hl7.org/fhir"></Parameters>, <Patient xmlns="http://hl7.org/fhir"><birthDate value="1920-01-01"/></Patient>
+		Replace Primitive, <Patient xmlns="http://hl7.org/fhir"><birthDate value="1920-01-01"/></Patient>, <Parameters xmlns="http://hl7.org/fhir"><parameter><name value="operation"/><part><name value="type"/><valueCode value="replace"/></part><part><name value="path"/><valueString value="Patient.birthDate"/></part><part><name value="value"/><valueDate value="1930-01-01"/></part></parameter></Parameters>, <Patient xmlns="http://hl7.org/fhir"><birthDate value="1930-01-01"/></Patient>
+		Delete Primitive, <Patient xmlns="http://hl7.org/fhir"><birthDate value="1920-01-01"/></Patient>, <Parameters xmlns="http://hl7.org/fhir"><parameter><name value="operation"/><part><name value="type"/><valueCode value="delete"/></part><part><name value="path"/><valueString value="Patient.birthDate"/></part></parameter></Parameters>, <Patient xmlns="http://hl7.org/fhir"></Patient>
+		Add Primitive, <Patient xmlns="http://hl7.org/fhir"></Patient>, <Parameters xmlns="http://hl7.org/fhir"><parameter><name value="operation"/><part><name value="type"/><valueCode value="add"/></part><part><name value="path"/><valueString value="Patient"/></part><part><name value="name"/><valueString value="birthDate"/></part><part><name value="value"/><valueDate value="1930-01-01"/></part></parameter></Parameters>, <Patient xmlns="http://hl7.org/fhir"><birthDate value="1930-01-01"/></Patient>
+		Delete Primitive #2, <Patient xmlns="http://hl7.org/fhir"><birthDate value="1920-01-01"/></Patient>, <Parameters xmlns="http://hl7.org/fhir"><parameter><name value="operation"/><part><name value="type"/><valueCode value="delete"/></part><part><name value="path"/><valueString value="Patient.birthDate"/></part></parameter></Parameters>, <Patient xmlns="http://hl7.org/fhir"></Patient>
+		Replace Nested Primitive #1, <Patient xmlns="http://hl7.org/fhir"><contact><name><text value="a name"/></name><gender value="male"/></contact></Patient>, <Parameters xmlns="http://hl7.org/fhir"><parameter><name value="operation"/><part><name value="type"/><valueCode value="replace"/></part><part><name value="path"/><valueString value="Patient.contact[0].gender"/></part><part><name value="value"/><valueCode value="female"/></part></parameter></Parameters>, <Patient xmlns="http://hl7.org/fhir"><contact><name><text value="a name"/></name><gender value="female"/></contact></Patient>
+		Replace Nested Primitive #2, <Patient xmlns="http://hl7.org/fhir"><contact><name><text value="a name"/></name><gender value="male"/></contact></Patient>, <Parameters xmlns="http://hl7.org/fhir"><parameter><name value="operation"/><part><name value="type"/><valueCode value="replace"/></part><part><name value="path"/><valueString value="Patient.contact[0].name.text"/></part><part><name value="value"/><valueString value="the name"/></part></parameter></Parameters>, <Patient xmlns="http://hl7.org/fhir"><contact><name><text value="the name"/></name><gender value="male"/></contact></Patient>
+		Delete Nested Primitive #1, <Patient xmlns="http://hl7.org/fhir"><contact><name><text value="a name"/></name><gender value="male"/></contact></Patient>, <Parameters xmlns="http://hl7.org/fhir"><parameter><name value="operation"/><part><name value="type"/><valueCode value="delete"/></part><part><name value="path"/><valueString value="Patient.contact[0].gender"/></part></parameter></Parameters>, <Patient xmlns="http://hl7.org/fhir"><contact><name><text value="a name"/></name></contact></Patient>
+		Delete Nested Primitive #2, <Patient xmlns="http://hl7.org/fhir"><contact><name><text value="a name"/></name><gender value="male"/></contact></Patient>, <Parameters xmlns="http://hl7.org/fhir"><parameter><name value="operation"/><part><name value="type"/><valueCode value="delete"/></part><part><name value="path"/><valueString value="Patient.contact[0].name.text"/></part></parameter></Parameters>, <Patient xmlns="http://hl7.org/fhir"><contact><gender value="male"/></contact></Patient>
+		Add Nested Primitive, <Patient xmlns="http://hl7.org/fhir"><contact><name><text value="a name"/></name></contact></Patient>, <Parameters xmlns="http://hl7.org/fhir"><parameter><name value="operation"/><part><name value="type"/><valueCode value="add"/></part><part><name value="path"/><valueString value="Patient.contact[0]"/></part><part><name value="name"/><valueString value="gender"/></part><part><name value="value"/><valueCode value="male"/></part></parameter></Parameters>, <Patient xmlns="http://hl7.org/fhir"><contact><name><text value="a name"/></name><gender value="male"/></contact></Patient>
+		Add Complex, <Patient xmlns="http://hl7.org/fhir"></Patient>, <Parameters xmlns="http://hl7.org/fhir"><parameter><name value="operation"/><part><name value="type"/><valueCode value="add"/></part><part><name value="path"/><valueString value="Patient"/></part><part><name value="name"/><valueString value="maritalStatus"/></part><part><name value="value"/><valueCodeableConcept><text value="married"/></valueCodeableConcept></part></parameter></Parameters>, <Patient xmlns="http://hl7.org/fhir"><maritalStatus><text value="married"/></maritalStatus></Patient>
+		Replace Complex, <Patient xmlns="http://hl7.org/fhir"><maritalStatus id="1"><text value="married"/></maritalStatus></Patient>, <Parameters xmlns="http://hl7.org/fhir"><parameter><name value="operation"/><part><name value="type"/><valueCode value="replace"/></part><part><name value="path"/><valueString value="Patient.maritalStatus"/></part><part><name value="value"/><valueCodeableConcept id="2"><text value="not married"/></valueCodeableConcept></part></parameter></Parameters>, <Patient xmlns="http://hl7.org/fhir"><maritalStatus id="2"><text value="not married"/></maritalStatus></Patient>
+		Delete Complex, <Patient xmlns="http://hl7.org/fhir"><maritalStatus><text value="married"/></maritalStatus></Patient>, <Parameters xmlns="http://hl7.org/fhir"><parameter><name value="operation"/><part><name value="type"/><valueCode value="delete"/></part><part><name value="path"/><valueString value="Patient.maritalStatus"/></part></parameter></Parameters>, <Patient xmlns="http://hl7.org/fhir"></Patient>
+		Add Anonymous Type, <Patient xmlns="http://hl7.org/fhir"></Patient>, <Parameters xmlns="http://hl7.org/fhir"><parameter><name value="operation"/><part><name value="type"/><valueCode value="add"/></part><part><name value="path"/><valueString value="Patient"/></part><part><name value="name"/><valueString value="contact"/></part><part><name value="value"/><part><name value="name"/><valueHumanName><text value="a name"/></valueHumanName></part></part></parameter></Parameters>, <Patient xmlns="http://hl7.org/fhir"><contact><name><text value="a name"/></name></contact></Patient>
+		Delete Anonymous Type, <Patient xmlns="http://hl7.org/fhir"><contact><name><text value="a name"/></name></contact></Patient>, <Parameters xmlns="http://hl7.org/fhir"><parameter><name value="operation"/><part><name value="type"/><valueCode value="delete"/></part><part><name value="path"/><valueString value="Patient.contact[0]"/></part></parameter></Parameters>, <Patient xmlns="http://hl7.org/fhir"></Patient>
+		List unchanged, <Patient xmlns="http://hl7.org/fhir"><identifier><system value="http://example.org"/><value value="value 1"/></identifier><identifier><system value="http://example.org"/><value value="value 2"/></identifier></Patient>, <Parameters xmlns="http://hl7.org/fhir"></Parameters>, <Patient xmlns="http://hl7.org/fhir"><identifier><system value="http://example.org"/><value value="value 1"/></identifier><identifier><system value="http://example.org"/><value value="value 2"/></identifier></Patient>
+		List unchanged contents changed, <Patient xmlns="http://hl7.org/fhir"><identifier id="a"><system value="http://example.org"/><value value="value 1"/></identifier><identifier id="b"><system value="http://example.org"/><value value="value 2"/></identifier></Patient>, <Parameters xmlns="http://hl7.org/fhir"><parameter><name value="operation"/><part><name value="type"/><valueCode value="replace"/></part><part><name value="path"/><valueString value="Patient.identifier[0].value"/></part><part><name value="value"/><valueString value="value 2"/></part></parameter><parameter><name value="operation"/><part><name value="type"/><valueCode value="replace"/></part><part><name value="path"/><valueString value="Patient.identifier[1].value"/></part><part><name value="value"/><valueString value="value 1"/></part></parameter></Parameters>, <Patient xmlns="http://hl7.org/fhir"><identifier id="a"><system value="http://example.org"/><value value="value 2"/></identifier><identifier id="b"><system value="http://example.org"/><value value="value 1"/></identifier></Patient>
+		Add to list, <Patient xmlns="http://hl7.org/fhir"><identifier><system value="http://example.org"/><value value="value 1"/></identifier><identifier><system value="http://example.org"/><value value="value 2"/></identifier></Patient>, <Parameters xmlns="http://hl7.org/fhir"><parameter><name value="operation"/><part><name value="type"/><valueCode value="insert"/></part><part><name value="path"/><valueString value="Patient.identifier"/></part><part><name value="index"/><valueInteger value="2"/></part><part><name value="value"/><valueIdentifier><system value="http://example.org"/><value value="value 3"/></valueIdentifier></part></parameter></Parameters>, <Patient xmlns="http://hl7.org/fhir"><identifier><system value="http://example.org"/><value value="value 1"/></identifier><identifier><system value="http://example.org"/><value value="value 2"/></identifier><identifier><system value="http://example.org"/><value value="value 3"/></identifier></Patient>
+		Insert in list #1, <Patient xmlns="http://hl7.org/fhir"><identifier><system value="http://example.org"/><value value="value 1"/></identifier><identifier><system value="http://example.org"/><value value="value 2"/></identifier></Patient>, <Parameters xmlns="http://hl7.org/fhir"><parameter><name value="operation"/><part><name value="type"/><valueCode value="insert"/></part><part><name value="path"/><valueString value="Patient.identifier"/></part><part><name value="index"/><valueInteger value="1"/></part><part><name value="value"/><valueIdentifier><system value="http://example.org"/><value value="value 3"/></valueIdentifier></part></parameter></Parameters>, <Patient xmlns="http://hl7.org/fhir"><identifier><system value="http://example.org"/><value value="value 1"/></identifier><identifier><system value="http://example.org"/><value value="value 3"/></identifier><identifier><system value="http://example.org"/><value value="value 2"/></identifier></Patient>
+		Insert in list #2, <Patient xmlns="http://hl7.org/fhir"><identifier><system value="http://example.org"/><value value="value 1"/></identifier><identifier><system value="http://example.org"/><value value="value 2"/></identifier></Patient>, <Parameters xmlns="http://hl7.org/fhir"><parameter><name value="operation"/><part><name value="type"/><valueCode value="insert"/></part><part><name value="path"/><valueString value="Patient.identifier"/></part><part><name value="index"/><valueInteger value="0"/></part><part><name value="value"/><valueIdentifier><system value="http://example.org"/><value value="value 3"/></valueIdentifier></part></parameter></Parameters>, <Patient xmlns="http://hl7.org/fhir"><identifier><system value="http://example.org"/><value value="value 3"/></identifier><identifier><system value="http://example.org"/><value value="value 1"/></identifier><identifier><system value="http://example.org"/><value value="value 2"/></identifier></Patient>
+		Delete from List #1, <Patient xmlns="http://hl7.org/fhir"><identifier><system value="http://example.org"/><value value="value 1"/></identifier><identifier><system value="http://example.org"/><value value="value 2"/></identifier><identifier><system value="http://example.org"/><value value="value 3"/></identifier></Patient>, <Parameters xmlns="http://hl7.org/fhir"><parameter><name value="operation"/><part><name value="type"/><valueCode value="delete"/></part><part><name value="path"/><valueString value="Patient.identifier[0]"/></part></parameter></Parameters>, <Patient xmlns="http://hl7.org/fhir"><identifier><system value="http://example.org"/><value value="value 2"/></identifier><identifier><system value="http://example.org"/><value value="value 3"/></identifier></Patient>
+		Delete from List #2, <Patient xmlns="http://hl7.org/fhir"><identifier><system value="http://example.org"/><value value="value 1"/></identifier><identifier><system value="http://example.org"/><value value="value 2"/></identifier><identifier><system value="http://example.org"/><value value="value 3"/></identifier></Patient>, <Parameters xmlns="http://hl7.org/fhir"><parameter><name value="operation"/><part><name value="type"/><valueCode value="delete"/></part><part><name value="path"/><valueString value="Patient.identifier[1]"/></part></parameter></Parameters>, <Patient xmlns="http://hl7.org/fhir"><identifier><system value="http://example.org"/><value value="value 1"/></identifier><identifier><system value="http://example.org"/><value value="value 3"/></identifier></Patient>
+		Delete from List #3, <Patient xmlns="http://hl7.org/fhir"><identifier><system value="http://example.org"/><value value="value 1"/></identifier><identifier><system value="http://example.org"/><value value="value 2"/></identifier><identifier><system value="http://example.org"/><value value="value 3"/></identifier></Patient>, <Parameters xmlns="http://hl7.org/fhir"><parameter><name value="operation"/><part><name value="type"/><valueCode value="delete"/></part><part><name value="path"/><valueString value="Patient.identifier[2]"/></part></parameter></Parameters>, <Patient xmlns="http://hl7.org/fhir"><identifier><system value="http://example.org"/><value value="value 1"/></identifier><identifier><system value="http://example.org"/><value value="value 2"/></identifier></Patient>
+		Reorder List #1, <Patient xmlns="http://hl7.org/fhir"><identifier><system value="http://example.org"/><value value="value 1"/></identifier><identifier><system value="http://example.org"/><value value="value 2"/></identifier><identifier><system value="http://example.org"/><value value="value 3"/></identifier><identifier><system value="http://example.org"/><value value="value 4"/></identifier></Patient>, <Parameters xmlns="http://hl7.org/fhir"><parameter><name value="operation"/><part><name value="type"/><valueCode value="move"/></part><part><name value="path"/><valueString value="Patient.identifier"/></part><part><name value="source"/><valueInteger value="3"/></part><part><name value="destination"/><valueInteger value="1"/></part></parameter></Parameters>, <Patient xmlns="http://hl7.org/fhir"><identifier><system value="http://example.org"/><value value="value 1"/></identifier><identifier><system value="http://example.org"/><value value="value 4"/></identifier><identifier><system value="http://example.org"/><value value="value 2"/></identifier><identifier><system value="http://example.org"/><value value="value 3"/></identifier></Patient>
+		Reorder List #2, <Patient xmlns="http://hl7.org/fhir"><identifier><system value="http://example.org"/><value value="value 1"/></identifier><identifier><system value="http://example.org"/><value value="value 2"/></identifier><identifier><system value="http://example.org"/><value value="value 3"/></identifier><identifier><system value="http://example.org"/><value value="value 4"/></identifier></Patient>, <Parameters xmlns="http://hl7.org/fhir"><parameter><name value="operation"/><part><name value="type"/><valueCode value="move"/></part><part><name value="path"/><valueString value="Patient.identifier"/></part><part><name value="source"/><valueInteger value="3"/></part><part><name value="destination"/><valueInteger value="0"/></part></parameter></Parameters>, <Patient xmlns="http://hl7.org/fhir"><identifier><system value="http://example.org"/><value value="value 4"/></identifier><identifier><system value="http://example.org"/><value value="value 1"/></identifier><identifier><system value="http://example.org"/><value value="value 2"/></identifier><identifier><system value="http://example.org"/><value value="value 3"/></identifier></Patient>
+		Reorder List #3, <Patient xmlns="http://hl7.org/fhir"><identifier><system value="http://example.org"/><value value="value 1"/></identifier><identifier><system value="http://example.org"/><value value="value 2"/></identifier><identifier><system value="http://example.org"/><value value="value 3"/></identifier><identifier><system value="http://example.org"/><value value="value 4"/></identifier></Patient>, <Parameters xmlns="http://hl7.org/fhir"><parameter><name value="operation"/><part><name value="type"/><valueCode value="move"/></part><part><name value="path"/><valueString value="Patient.identifier"/></part><part><name value="source"/><valueInteger value="3"/></part><part><name value="destination"/><valueInteger value="2"/></part></parameter></Parameters>, <Patient xmlns="http://hl7.org/fhir"><identifier><system value="http://example.org"/><value value="value 1"/></identifier><identifier><system value="http://example.org"/><value value="value 2"/></identifier><identifier><system value="http://example.org"/><value value="value 4"/></identifier><identifier><system value="http://example.org"/><value value="value 3"/></identifier></Patient>
+		Reorder List #4, <Patient xmlns="http://hl7.org/fhir"><identifier><system value="http://example.org"/><value value="value 1"/></identifier><identifier><system value="http://example.org"/><value value="value 2"/></identifier><identifier><system value="http://example.org"/><value value="value 3"/></identifier><identifier><system value="http://example.org"/><value value="value 4"/></identifier></Patient>, <Parameters xmlns="http://hl7.org/fhir"><parameter><name value="operation"/><part><name value="type"/><valueCode value="move"/></part><part><name value="path"/><valueString value="Patient.identifier"/></part><part><name value="source"/><valueInteger value="0"/></part><part><name value="destination"/><valueInteger value="3"/></part></parameter></Parameters>, <Patient xmlns="http://hl7.org/fhir"><identifier><system value="http://example.org"/><value value="value 2"/></identifier><identifier><system value="http://example.org"/><value value="value 3"/></identifier><identifier><system value="http://example.org"/><value value="value 4"/></identifier><identifier><system value="http://example.org"/><value value="value 1"/></identifier></Patient>
+		Reorder List #5, <Patient xmlns="http://hl7.org/fhir"><identifier><system value="http://example.org"/><value value="value 1"/></identifier><identifier><system value="http://example.org"/><value value="value 2"/></identifier><identifier><system value="http://example.org"/><value value="value 3"/></identifier><identifier><system value="http://example.org"/><value value="value 4"/></identifier></Patient>, <Parameters xmlns="http://hl7.org/fhir"><parameter><name value="operation"/><part><name value="type"/><valueCode value="move"/></part><part><name value="path"/><valueString value="Patient.identifier"/></part><part><name value="source"/><valueInteger value="1"/></part><part><name value="destination"/><valueInteger value="0"/></part></parameter><parameter><name value="operation"/><part><name value="type"/><valueCode value="move"/></part><part><name value="path"/><valueString value="Patient.identifier"/></part><part><name value="source"/><valueInteger value="2"/></part><part><name value="destination"/><valueInteger value="1"/></part></parameter></Parameters>, <Patient xmlns="http://hl7.org/fhir"><identifier><system value="http://example.org"/><value value="value 2"/></identifier><identifier><system value="http://example.org"/><value value="value 3"/></identifier><identifier><system value="http://example.org"/><value value="value 1"/></identifier><identifier><system value="http://example.org"/><value value="value 4"/></identifier></Patient>
+		Reorder List #6, <Patient xmlns="http://hl7.org/fhir"><identifier><system value="http://example.org"/><value value="value 1"/></identifier><identifier><system value="http://example.org"/><value value="value 2"/></identifier><identifier><system value="http://example.org"/><value value="value 3"/></identifier><identifier><system value="http://example.org"/><value value="value 4"/></identifier></Patient>, <Parameters xmlns="http://hl7.org/fhir"><parameter><name value="operation"/><part><name value="type"/><valueCode value="move"/></part><part><name value="path"/><valueString value="Patient.identifier"/></part><part><name value="source"/><valueInteger value="3"/></part><part><name value="destination"/><valueInteger value="0"/></part></parameter><parameter><name value="operation"/><part><name value="type"/><valueCode value="move"/></part><part><name value="path"/><valueString value="Patient.identifier"/></part><part><name value="source"/><valueInteger value="3"/></part><part><name value="destination"/><valueInteger value="1"/></part></parameter><parameter><name value="operation"/><part><name value="type"/><valueCode value="move"/></part><part><name value="path"/><valueString value="Patient.identifier"/></part><part><name value="source"/><valueInteger value="3"/></part><part><name value="destination"/><valueInteger value="2"/></part></parameter></Parameters>, <Patient xmlns="http://hl7.org/fhir"><identifier><system value="http://example.org"/><value value="value 4"/></identifier><identifier><system value="http://example.org"/><value value="value 3"/></identifier><identifier><system value="http://example.org"/><value value="value 2"/></identifier><identifier><system value="http://example.org"/><value value="value 1"/></identifier></Patient>
+		""")
+	public void testHL7Cases(String theName, String theInputResource, String thePatch, String theOutputResource) throws Exception {
+		IParser parser = ourCtx.newXmlParser();
+		Patient patient = parser.parseResource(Patient.class, theInputResource);
+		Parameters parameters = parser.parseResource(Parameters.class, thePatch);
+		Patient expectedPatient = parser.parseResource(Patient.class, theOutputResource);
+
+		FhirPatch svc = new FhirPatch(ourCtx);
+		svc.apply(patient, parameters);
+
+		new XmlExpectationsHelper().assertXmlEqual(theOutputResource, parser.encodeResourceToString(patient));
+		assertTrue(expectedPatient.equalsDeep(patient), theName);
+	}
 }
diff --git a/hapi-fhir-storage/src/main/java/ca/uhn/fhir/jpa/patch/FhirPatch.java b/hapi-fhir-storage/src/main/java/ca/uhn/fhir/jpa/patch/FhirPatch.java
index 4aa6e60f2a5..4b1f882debf 100644
--- a/hapi-fhir-storage/src/main/java/ca/uhn/fhir/jpa/patch/FhirPatch.java
+++ b/hapi-fhir-storage/src/main/java/ca/uhn/fhir/jpa/patch/FhirPatch.java
@@ -53,6 +53,20 @@ import static org.apache.commons.lang3.StringUtils.isNotBlank;
 
 public class FhirPatch {
 
+	public static final String OPERATION_ADD = "add";
+	public static final String OPERATION_DELETE = "delete";
+	public static final String OPERATION_INSERT = "insert";
+	public static final String OPERATION_MOVE = "move";
+	public static final String OPERATION_REPLACE = "replace";
+	public static final String PARAMETER_DESTINATION = "destination";
+	public static final String PARAMETER_INDEX = "index";
+	public static final String PARAMETER_NAME = "name";
+	public static final String PARAMETER_OPERATION = "operation";
+	public static final String PARAMETER_PATH = "path";
+	public static final String PARAMETER_SOURCE = "source";
+	public static final String PARAMETER_TYPE = "type";
+	public static final String PARAMETER_VALUE = "value";
+
 	private final FhirContext myContext;
 	private boolean myIncludePreviousValueInDiff;
 	private Set<EncodeContextPath> myIgnorePaths = Collections.emptySet();
@@ -81,232 +95,288 @@ public class FhirPatch {
 
 	public void apply(IBaseResource theResource, IBaseResource thePatch) {
 
-		List<IBase> opParameters = ParametersUtil.getNamedParameters(myContext, thePatch, "operation");
-		for (IBase nextOp : opParameters) {
-			String type = ParametersUtil.getParameterPartValueAsString(myContext, nextOp, "type");
-			String path = ParametersUtil.getParameterPartValueAsString(myContext, nextOp, "path");
-			Optional<IBase> valuePart = ParametersUtil.getParameterPart(myContext, nextOp, "value");
-			Optional<IBase> valuePartValue = ParametersUtil.getParameterPartValue(myContext, nextOp, "value");
-
+		List<IBase> opParameters = ParametersUtil.getNamedParameters(myContext, thePatch, PARAMETER_OPERATION);
+		for (IBase nextOperation : opParameters) {
+			String type = ParametersUtil.getParameterPartValueAsString(myContext, nextOperation, PARAMETER_TYPE);
 			type = defaultString(type);
-			path = defaultString(path);
-
-			String containingPath;
-			String elementName;
-			Integer removeIndex = null;
-			Integer insertIndex = null;
-			if ("delete".equals(type)) {
-				if (path.endsWith(")")) {
-					// This is probably a filter, so we're probably dealing with a list
-					int filterArgsIndex = path.lastIndexOf('('); // Let's hope there aren't nested parentheses
-					int lastDotIndex = path.lastIndexOf('.', filterArgsIndex); // There might be a dot inside the parentheses, so look to the left of that
-					int secondLastDotIndex = path.lastIndexOf('.', lastDotIndex-1);
-					containingPath = path.substring(0, secondLastDotIndex);
-					elementName = path.substring(secondLastDotIndex + 1, lastDotIndex);
-				} else if (path.endsWith("]")) {
-					// This is almost definitely a list
-					int openBracketIndex = path.lastIndexOf('[');
-					int lastDotIndex = path.lastIndexOf('.', openBracketIndex);
-					containingPath = path.substring(0, lastDotIndex);
-					elementName = path.substring(lastDotIndex + 1, openBracketIndex);
-				} else {
-					doDelete(theResource, path);
-					continue;
-				}
-
-			} else if ("add".equals(type)) {
-
-				containingPath = path;
-				elementName = ParametersUtil.getParameterPartValueAsString(myContext, nextOp, "name");
-
-			} else if ("replace".equals(type)) {
-
-				int lastDot = path.lastIndexOf(".");
-				containingPath = path.substring(0, lastDot);
-				elementName = path.substring(lastDot + 1);
-
-			} else if ("insert".equals(type)) {
-
-				int lastDot = path.lastIndexOf(".");
-				containingPath = path.substring(0, lastDot);
-				elementName = path.substring(lastDot + 1);
-				insertIndex = ParametersUtil
-					.getParameterPartValue(myContext, nextOp, "index")
-					.map(t -> (IPrimitiveType<Integer>) t)
-					.map(t -> t.getValue())
-					.orElseThrow(() -> new InvalidRequestException("No index supplied for insert operation"));
-
-			} else if ("move".equals(type)) {
-
-				int lastDot = path.lastIndexOf(".");
-				containingPath = path.substring(0, lastDot);
-				elementName = path.substring(lastDot + 1);
-				insertIndex = ParametersUtil
-					.getParameterPartValue(myContext, nextOp, "destination")
-					.map(t -> (IPrimitiveType<Integer>) t)
-					.map(t -> t.getValue())
-					.orElseThrow(() -> new InvalidRequestException("No index supplied for insert operation"));
-				removeIndex = ParametersUtil
-					.getParameterPartValue(myContext, nextOp, "source")
-					.map(t -> (IPrimitiveType<Integer>) t)
-					.map(t -> t.getValue())
-					.orElseThrow(() -> new InvalidRequestException("No index supplied for insert operation"));
 
+			if (OPERATION_DELETE.equals(type)) {
+				handleDeleteOperation(theResource, nextOperation);
+			} else if (OPERATION_ADD.equals(type)) {
+				handleAddOperation(theResource, nextOperation);
+			} else if (OPERATION_REPLACE.equals(type)) {
+				handleReplaceOperation(theResource, nextOperation);
+			} else if (OPERATION_INSERT.equals(type)) {
+				handleInsertOperation(theResource, nextOperation);
+			} else if (OPERATION_MOVE.equals(type)) {
+				handleMoveOperation(theResource, nextOperation);
 			} else {
-
 				throw new InvalidRequestException(Msg.code(1267) + "Unknown patch operation type: " + type);
-
 			}
-
-			List<IBase> paths = myContext.newFhirPath().evaluate(theResource, containingPath, IBase.class);
-			for (IBase next : paths) {
-
-				BaseRuntimeElementDefinition<?> elementDef = myContext.getElementDefinition(next.getClass());
-
-				String childName = elementName;
-				BaseRuntimeChildDefinition childDef = elementDef.getChildByName(childName);
-				BaseRuntimeElementDefinition<?> childElement;
-				if (childDef == null) {
-					childName = elementName + "[x]";
-					childDef = elementDef.getChildByName(childName);
-					childElement = childDef.getChildByName(childDef.getValidChildNames().iterator().next());
-				} else {
-					childElement = childDef.getChildByName(childName);
-				}
-
-				if ("move".equals(type)) {
-
-					List<IBase> existingValues = new ArrayList<>(childDef.getAccessor().getValues(next));
-					if (removeIndex == null || removeIndex >= existingValues.size()) {
-						String msg = myContext.getLocalizer().getMessage(FhirPatch.class, "invalidMoveSourceIndex", removeIndex, path, existingValues.size());
-						throw new InvalidRequestException(Msg.code(1268) + msg);
-					}
-					IBase newValue = existingValues.remove(removeIndex.intValue());
-
-					if (insertIndex == null || insertIndex > existingValues.size()) {
-						String msg = myContext.getLocalizer().getMessage(FhirPatch.class, "invalidMoveDestinationIndex", insertIndex, path, existingValues.size());
-						throw new InvalidRequestException(Msg.code(1269) + msg);
-					}
-					existingValues.add(insertIndex, newValue);
-
-					childDef.getMutator().setValue(next, null);
-					for (IBase nextNewValue : existingValues) {
-						childDef.getMutator().addValue(next, nextNewValue);
-					}
-
-					continue;
-				} else if ("delete".equals(type)) {
-					List<IBase> existingValues = new ArrayList<>(childDef.getAccessor().getValues(next));
-					List<IBase> elementsToRemove = myContext.newFhirPath().evaluate(theResource, path, IBase.class);
-					existingValues.removeAll(elementsToRemove);
-
-					childDef.getMutator().setValue(next, null);
-					for (IBase nextNewValue : existingValues) {
-						childDef.getMutator().addValue(next, nextNewValue);
-					}
-
-					continue;
-				}
-
-				IBase newValue;
-				if (valuePartValue.isPresent()) {
-					newValue = valuePartValue.get();
-				} else {
-					newValue = childElement.newInstance();
-
-					if (valuePart.isPresent()) {
-						List<IBase> valuePartParts = myContext.newTerser().getValues(valuePart.get(), "part");
-						for (IBase nextValuePartPart : valuePartParts) {
-
-							String name = myContext.newTerser().getSingleValue(nextValuePartPart, "name", IPrimitiveType.class).map(t -> t.getValueAsString()).orElse(null);
-							if (isNotBlank(name)) {
-
-								Optional<IBase> value = myContext.newTerser().getSingleValue(nextValuePartPart, "value[x]", IBase.class);
-								if (value.isPresent()) {
-
-									BaseRuntimeChildDefinition partChildDef = childElement.getChildByName(name);
-									if (partChildDef == null) {
-										name = name + "[x]";
-										partChildDef = childElement.getChildByName(name);
-									}
-									partChildDef.getMutator().addValue(newValue, value.get());
-
-								}
-
-							}
-
-						}
-					}
-
-				}
-
-				if (IBaseEnumeration.class.isAssignableFrom(childElement.getImplementingClass()) || XhtmlNode.class.isAssignableFrom(childElement.getImplementingClass())) {
-					// If the compositeElementDef is an IBaseEnumeration, we will use the actual compositeElementDef definition to build one, since
-					// it needs the right factory object passed to its constructor
-					IPrimitiveType<?> newValueInstance = (IPrimitiveType<?>) childElement.newInstance();
-					newValueInstance.setValueAsString(((IPrimitiveType<?>) newValue).getValueAsString());
-					childDef.getMutator().setValue(next, newValueInstance);
-					newValue = newValueInstance;
-				}
-
-				if ("insert".equals(type)) {
-
-					List<IBase> existingValues = new ArrayList<>(childDef.getAccessor().getValues(next));
-					if (insertIndex == null || insertIndex > existingValues.size()) {
-						String msg = myContext.getLocalizer().getMessage(FhirPatch.class, "invalidInsertIndex", insertIndex, path, existingValues.size());
-						throw new InvalidRequestException(Msg.code(1270) + msg);
-					}
-					existingValues.add(insertIndex, newValue);
-
-					childDef.getMutator().setValue(next, null);
-					for (IBase nextNewValue : existingValues) {
-						childDef.getMutator().addValue(next, nextNewValue);
-					}
-
-				} else if ("add".equals(type)) {
-					childDef.getMutator().addValue(next, newValue);
-				} else if ("replace".equals(type)) {
-					childDef.getMutator().setValue(next, newValue);
-				}
-			}
-
-
 		}
-
 	}
 
-	private void doDelete(IBaseResource theResource, String thePath) {
-		List<IBase> paths = myContext.newFhirPath().evaluate(theResource, thePath, IBase.class);
-		for (IBase next : paths) {
-			myContext.newTerser().visit(next, new IModelVisitor2() {
-				@Override
-				public boolean acceptElement(IBase theElement, List<IBase> theContainingElementPath, List<BaseRuntimeChildDefinition> theChildDefinitionPath, List<BaseRuntimeElementDefinition<?>> theElementDefinitionPath) {
-					if (theElement instanceof IPrimitiveType) {
-						((IPrimitiveType<?>) theElement).setValueAsString(null);
+	private void handleAddOperation(IBaseResource theResource, IBase theParameters) {
+
+		String path = ParametersUtil.getParameterPartValueAsString(myContext, theParameters, PARAMETER_PATH);
+		String elementName = ParametersUtil.getParameterPartValueAsString(myContext, theParameters, PARAMETER_NAME);
+
+		String containingPath = defaultString(path);
+
+		List<IBase> containingElements = myContext.newFhirPath().evaluate(theResource, containingPath, IBase.class);
+		for (IBase nextElement : containingElements) {
+			ChildDefinition childDefinition = findChildDefinition(nextElement, elementName);
+
+			IBase newValue = getNewValue(theParameters, nextElement, childDefinition);
+
+			childDefinition.getChildDef().getMutator().addValue(nextElement, newValue);
+		}
+	}
+
+	private void handleInsertOperation(IBaseResource theResource, IBase theParameters) {
+
+		String path = ParametersUtil.getParameterPartValueAsString(myContext, theParameters, PARAMETER_PATH);
+		path = defaultString(path);
+
+		int lastDot = path.lastIndexOf(".");
+		String containingPath = path.substring(0, lastDot);
+		String elementName = path.substring(lastDot + 1);
+		Integer insertIndex = ParametersUtil
+			.getParameterPartValueAsInteger(myContext, theParameters, PARAMETER_INDEX)
+			.orElseThrow(() -> new InvalidRequestException("No index supplied for insert operation"));
+
+		List<IBase> containingElements = myContext.newFhirPath().evaluate(theResource, containingPath, IBase.class);
+		for (IBase nextElement : containingElements) {
+
+			ChildDefinition childDefinition = findChildDefinition(nextElement, elementName);
+
+			IBase newValue = getNewValue(theParameters, nextElement, childDefinition);
+
+			List<IBase> existingValues = new ArrayList<>(childDefinition.getChildDef().getAccessor().getValues(nextElement));
+			if (insertIndex == null || insertIndex < 0 || insertIndex > existingValues.size()) {
+				String msg = myContext.getLocalizer().getMessage(FhirPatch.class, "invalidInsertIndex", insertIndex, path, existingValues.size());
+				throw new InvalidRequestException(Msg.code(1270) + msg);
+			}
+			existingValues.add(insertIndex, newValue);
+
+			childDefinition.getChildDef().getMutator().setValue(nextElement, null);
+			for (IBase nextNewValue : existingValues) {
+				childDefinition.getChildDef().getMutator().addValue(nextElement, nextNewValue);
+			}
+		}
+	}
+
+	private void handleDeleteOperation(IBaseResource theResource, IBase theParameters) {
+
+		String path = ParametersUtil.getParameterPartValueAsString(myContext, theParameters, PARAMETER_PATH);
+		path = defaultString(path);
+
+		String containingPath;
+		String elementName;
+
+		if (path.endsWith(")")) {
+			// This is probably a filter, so we're probably dealing with a list
+			int filterArgsIndex = path.lastIndexOf('('); // Let's hope there aren't nested parentheses
+			int lastDotIndex = path.lastIndexOf('.', filterArgsIndex); // There might be a dot inside the parentheses, so look to the left of that
+			int secondLastDotIndex = path.lastIndexOf('.', lastDotIndex-1);
+			containingPath = path.substring(0, secondLastDotIndex);
+			elementName = path.substring(secondLastDotIndex + 1, lastDotIndex);
+		} else if (path.endsWith("]")) {
+			// This is almost definitely a list
+			int openBracketIndex = path.lastIndexOf('[');
+			int lastDotIndex = path.lastIndexOf('.', openBracketIndex);
+			containingPath = path.substring(0, lastDotIndex);
+			elementName = path.substring(lastDotIndex + 1, openBracketIndex);
+		} else {
+			containingPath = path;
+			elementName = null;
+		}
+
+		List<IBase> containingElements = myContext.newFhirPath().evaluate(theResource, containingPath, IBase.class);
+		for (IBase nextElement : containingElements) {
+			if (elementName == null) {
+				deleteSingleElement(nextElement);
+			} else {
+				deleteFromList(theResource, nextElement, elementName, path);
+			}
+		}
+	}
+
+	private void deleteFromList(IBaseResource theResource, IBase theContainingElement, String theListElementName, String theElementToDeletePath) {
+		ChildDefinition childDefinition = findChildDefinition(theContainingElement, theListElementName);
+
+		List<IBase> existingValues = new ArrayList<>(childDefinition.getChildDef().getAccessor().getValues(theContainingElement));
+		List<IBase> elementsToRemove = myContext.newFhirPath().evaluate(theResource, theElementToDeletePath, IBase.class);
+		existingValues.removeAll(elementsToRemove);
+
+		childDefinition.getChildDef().getMutator().setValue(theContainingElement, null);
+		for (IBase nextNewValue : existingValues) {
+			childDefinition.getChildDef().getMutator().addValue(theContainingElement, nextNewValue);
+		}
+	}
+
+	private void handleReplaceOperation(IBaseResource theResource, IBase theParameters) {
+		String path = ParametersUtil.getParameterPartValueAsString(myContext, theParameters, PARAMETER_PATH);
+		path = defaultString(path);
+
+		int lastDot = path.lastIndexOf(".");
+		String containingPath = path.substring(0, lastDot);
+		String elementName = path.substring(lastDot + 1);
+
+		List<IBase> containingElements = myContext.newFhirPath().evaluate(theResource, containingPath, IBase.class);
+		for (IBase nextElement : containingElements) {
+
+			ChildDefinition childDefinition = findChildDefinition(nextElement, elementName);
+
+			IBase newValue = getNewValue(theParameters, nextElement, childDefinition);
+
+			childDefinition.getChildDef().getMutator().setValue(nextElement, newValue);
+		}
+	}
+
+	private void handleMoveOperation(IBaseResource theResource, IBase theParameters) {
+		String path = ParametersUtil.getParameterPartValueAsString(myContext, theParameters, PARAMETER_PATH);
+		path = defaultString(path);
+
+		int lastDot = path.lastIndexOf(".");
+		String containingPath = path.substring(0, lastDot);
+		String elementName = path.substring(lastDot + 1);
+		Integer insertIndex = ParametersUtil
+			.getParameterPartValueAsInteger(myContext, theParameters, PARAMETER_DESTINATION)
+			.orElseThrow(() -> new InvalidRequestException("No index supplied for move operation"));
+		Integer removeIndex = ParametersUtil
+			.getParameterPartValueAsInteger(myContext, theParameters, PARAMETER_SOURCE)
+			.orElseThrow(() -> new InvalidRequestException("No index supplied for move operation"));
+
+		List<IBase> containingElements = myContext.newFhirPath().evaluate(theResource, containingPath, IBase.class);
+		for (IBase nextElement : containingElements) {
+
+			ChildDefinition childDefinition = findChildDefinition(nextElement, elementName);
+
+			List<IBase> existingValues = new ArrayList<>(childDefinition.getChildDef().getAccessor().getValues(nextElement));
+			if (removeIndex == null || removeIndex < 0 || removeIndex >= existingValues.size()) {
+				String msg = myContext.getLocalizer().getMessage(FhirPatch.class, "invalidMoveSourceIndex", removeIndex, path, existingValues.size());
+				throw new InvalidRequestException(Msg.code(1268) + msg);
+			}
+			IBase newValue = existingValues.remove(removeIndex.intValue());
+
+			if (insertIndex == null || insertIndex < 0 || insertIndex > existingValues.size()) {
+				String msg = myContext.getLocalizer().getMessage(FhirPatch.class, "invalidMoveDestinationIndex", insertIndex, path, existingValues.size());
+				throw new InvalidRequestException(Msg.code(1269) + msg);
+			}
+			existingValues.add(insertIndex, newValue);
+
+			childDefinition.getChildDef().getMutator().setValue(nextElement, null);
+			for (IBase nextNewValue : existingValues) {
+				childDefinition.getChildDef().getMutator().addValue(nextElement, nextNewValue);
+			}
+		}
+	}
+
+	private ChildDefinition findChildDefinition(IBase theContainingElement, String theElementName) {
+		BaseRuntimeElementDefinition<?> elementDef = myContext.getElementDefinition(theContainingElement.getClass());
+
+		String childName = theElementName;
+		BaseRuntimeChildDefinition childDef = elementDef.getChildByName(childName);
+		BaseRuntimeElementDefinition<?> childElement;
+		if (childDef == null) {
+			childName = theElementName + "[x]";
+			childDef = elementDef.getChildByName(childName);
+			childElement = childDef.getChildByName(childDef.getValidChildNames().iterator().next());
+		} else {
+			childElement = childDef.getChildByName(childName);
+		}
+
+		return new ChildDefinition(childDef, childElement);
+	}
+
+	private IBase getNewValue(IBase theParameters, IBase theElement, ChildDefinition theChildDefinition) {
+		Optional<IBase> valuePart = ParametersUtil.getParameterPart(myContext, theParameters, PARAMETER_VALUE);
+		Optional<IBase> valuePartValue = ParametersUtil.getParameterPartValue(myContext, theParameters, PARAMETER_VALUE);
+
+		IBase newValue;
+		if (valuePartValue.isPresent()) {
+			newValue = valuePartValue.get();
+		} else {
+			newValue = theChildDefinition.getChildElement().newInstance();
+
+			if (valuePart.isPresent()) {
+				IBase theValueElement = valuePart.get();
+				populateNewValue(theChildDefinition, newValue, theValueElement);
+			}
+
+		}
+
+		if (IBaseEnumeration.class.isAssignableFrom(theChildDefinition.getChildElement().getImplementingClass()) || XhtmlNode.class.isAssignableFrom(theChildDefinition.getChildElement().getImplementingClass())) {
+			// If the compositeElementDef is an IBaseEnumeration, we will use the actual compositeElementDef definition to build one, since
+			// it needs the right factory object passed to its constructor
+			IPrimitiveType<?> newValueInstance;
+			if (theChildDefinition.getChildDef().getInstanceConstructorArguments() != null) {
+				newValueInstance = (IPrimitiveType<?>) theChildDefinition.getChildElement().newInstance(
+					theChildDefinition.getChildDef().getInstanceConstructorArguments());
+			} else {
+				newValueInstance = (IPrimitiveType<?>) theChildDefinition.getChildElement().newInstance();
+			}
+			newValueInstance.setValueAsString(((IPrimitiveType<?>) newValue).getValueAsString());
+			theChildDefinition.getChildDef().getMutator().setValue(theElement, newValueInstance);
+			newValue = newValueInstance;
+		}
+		return newValue;
+	}
+
+	private void populateNewValue(ChildDefinition theChildDefinition, IBase theNewValue, IBase theValueElement) {
+		List<IBase> valuePartParts = myContext.newTerser().getValues(theValueElement, "part");
+		for (IBase nextValuePartPart : valuePartParts) {
+
+			String name = myContext.newTerser().getSingleValue(nextValuePartPart, PARAMETER_NAME, IPrimitiveType.class).map(IPrimitiveType::getValueAsString).orElse(null);
+			if (isNotBlank(name)) {
+
+				Optional<IBase> value = myContext.newTerser().getSingleValue(nextValuePartPart, "value[x]", IBase.class);
+				if (value.isPresent()) {
+
+					BaseRuntimeChildDefinition partChildDef = theChildDefinition.getChildElement().getChildByName(name);
+					if (partChildDef == null) {
+						name = name + "[x]";
+						partChildDef = theChildDefinition.getChildElement().getChildByName(name);
 					}
-					return true;
+					partChildDef.getMutator().addValue(theNewValue, value.get());
+
 				}
 
-				@Override
-				public boolean acceptUndeclaredExtension(IBaseExtension<?, ?> theNextExt, List<IBase> theContainingElementPath, List<BaseRuntimeChildDefinition> theChildDefinitionPath, List<BaseRuntimeElementDefinition<?>> theElementDefinitionPath) {
-					theNextExt.setUrl(null);
-					theNextExt.setValue(null);
-					return true;
-				}
-			});
+			}
+
 		}
 	}
 
+	private void deleteSingleElement(IBase theElementToDelete) {
+		myContext.newTerser().visit(theElementToDelete, new IModelVisitor2() {
+			@Override
+			public boolean acceptElement(IBase theElement, List<IBase> theContainingElementPath, List<BaseRuntimeChildDefinition> theChildDefinitionPath, List<BaseRuntimeElementDefinition<?>> theElementDefinitionPath) {
+				if (theElement instanceof IPrimitiveType) {
+					((IPrimitiveType<?>) theElement).setValueAsString(null);
+				}
+				return true;
+			}
+
+			@Override
+			public boolean acceptUndeclaredExtension(IBaseExtension<?, ?> theNextExt, List<IBase> theContainingElementPath, List<BaseRuntimeChildDefinition> theChildDefinitionPath, List<BaseRuntimeElementDefinition<?>> theElementDefinitionPath) {
+				theNextExt.setUrl(null);
+				theNextExt.setValue(null);
+				return true;
+			}
+		});
+	}
+
 	public IBaseParameters diff(@Nullable IBaseResource theOldValue, @Nonnull IBaseResource theNewValue) {
 		IBaseParameters retVal = ParametersUtil.newInstance(myContext);
 		String newValueTypeName = myContext.getResourceDefinition(theNewValue).getName();
 
 		if (theOldValue == null) {
 
-			IBase operation = ParametersUtil.addParameterToParameters(myContext, retVal, "operation");
-			ParametersUtil.addPartCode(myContext, operation, "type", "insert");
-			ParametersUtil.addPartString(myContext, operation, "path", newValueTypeName);
-			ParametersUtil.addPart(myContext, operation, "value", theNewValue);
+			IBase operation = ParametersUtil.addParameterToParameters(myContext, retVal, PARAMETER_OPERATION);
+			ParametersUtil.addPartCode(myContext, operation, PARAMETER_TYPE, OPERATION_INSERT);
+			ParametersUtil.addPartString(myContext, operation, PARAMETER_PATH, newValueTypeName);
+			ParametersUtil.addPart(myContext, operation, PARAMETER_VALUE, theNewValue);
 
 		} else {
 
@@ -339,9 +409,9 @@ public class FhirPatch {
 		BaseRuntimeElementDefinition<?> sourceDef = myContext.getElementDefinition(theOldField.getClass());
 		BaseRuntimeElementDefinition<?> targetDef = myContext.getElementDefinition(theNewField.getClass());
 		if (!sourceDef.getName().equals(targetDef.getName())) {
-			IBase operation = ParametersUtil.addParameterToParameters(myContext, theDiff, "operation");
-			ParametersUtil.addPartCode(myContext, operation, "type", "replace");
-			ParametersUtil.addPartString(myContext, operation, "path", theTargetPath);
+			IBase operation = ParametersUtil.addParameterToParameters(myContext, theDiff, PARAMETER_OPERATION);
+			ParametersUtil.addPartCode(myContext, operation, PARAMETER_TYPE, OPERATION_REPLACE);
+			ParametersUtil.addPartString(myContext, operation, PARAMETER_PATH, theTargetPath);
 			addValueToDiff(operation, theOldField, theNewField);
 		} else {
 			if (theOldField instanceof IPrimitiveType) {
@@ -350,9 +420,9 @@ public class FhirPatch {
 				String oldValueAsString = toValue(oldPrimitive);
 				String newValueAsString = toValue(newPrimitive);
 				if (!Objects.equals(oldValueAsString, newValueAsString)) {
-					IBase operation = ParametersUtil.addParameterToParameters(myContext, theDiff, "operation");
-					ParametersUtil.addPartCode(myContext, operation, "type", "replace");
-					ParametersUtil.addPartString(myContext, operation, "path", theTargetPath);
+					IBase operation = ParametersUtil.addParameterToParameters(myContext, theDiff, PARAMETER_OPERATION);
+					ParametersUtil.addPartCode(myContext, operation, PARAMETER_TYPE, OPERATION_REPLACE);
+					ParametersUtil.addPartString(myContext, operation, PARAMETER_PATH, theTargetPath);
 					addValueToDiff(operation, oldPrimitive, newPrimitive);
 				}
 			}
@@ -405,9 +475,9 @@ public class FhirPatch {
 
 		// Find deleted items
 		while (sourceIndex < sourceValues.size()) {
-			IBase operation = ParametersUtil.addParameterToParameters(myContext, theDiff, "operation");
-			ParametersUtil.addPartCode(myContext, operation, "type", "delete");
-			ParametersUtil.addPartString(myContext, operation, "path", theTargetPath + "." + elementName + (repeatable ? "[" + targetIndex + "]" : ""));
+			IBase operation = ParametersUtil.addParameterToParameters(myContext, theDiff, PARAMETER_OPERATION);
+			ParametersUtil.addPartCode(myContext, operation, PARAMETER_TYPE, OPERATION_DELETE);
+			ParametersUtil.addPartString(myContext, operation, PARAMETER_PATH, theTargetPath + "." + elementName + (repeatable ? "[" + targetIndex + "]" : ""));
 
 			sourceIndex++;
 			targetIndex++;
@@ -417,10 +487,10 @@ public class FhirPatch {
 	}
 
 	private void addInsertItems(IBaseParameters theDiff, List<? extends IBase> theTargetValues, int theTargetIndex, String thePath, BaseRuntimeChildDefinition theChildDefinition) {
-		IBase operation = ParametersUtil.addParameterToParameters(myContext, theDiff, "operation");
-		ParametersUtil.addPartCode(myContext, operation, "type", "insert");
-		ParametersUtil.addPartString(myContext, operation, "path", thePath);
-		ParametersUtil.addPartInteger(myContext, operation, "index", theTargetIndex);
+		IBase operation = ParametersUtil.addParameterToParameters(myContext, theDiff, PARAMETER_OPERATION);
+		ParametersUtil.addPartCode(myContext, operation, PARAMETER_TYPE, OPERATION_INSERT);
+		ParametersUtil.addPartString(myContext, operation, PARAMETER_PATH, thePath);
+		ParametersUtil.addPartInteger(myContext, operation, PARAMETER_INDEX, theTargetIndex);
 
 		IBase value = theTargetValues.get(theTargetIndex);
 		BaseRuntimeElementDefinition<?> valueDef = myContext.getElementDefinition(value.getClass());
@@ -432,7 +502,7 @@ public class FhirPatch {
 		 * childen in instead.
 		 */
 		if (valueDef.isStandardType()) {
-			ParametersUtil.addPart(myContext, operation, "value", value);
+			ParametersUtil.addPart(myContext, operation, PARAMETER_VALUE, value);
 		} else {
 			for (BaseRuntimeChildDefinition nextChild : valueDef.getChildren()) {
 				List<IBase> childValues = nextChild.getAccessor().getValues(value);
@@ -454,7 +524,7 @@ public class FhirPatch {
 		}
 
 		IBase newValue = massageValueForDiff(theNewValue);
-		ParametersUtil.addPart(myContext, theOperationPart, "value", newValue);
+		ParametersUtil.addPart(myContext, theOperationPart, PARAMETER_VALUE, newValue);
 	}
 
 	private boolean pathIsIgnored(EncodeContextPath theSourceEncodeContext) {
@@ -469,19 +539,21 @@ public class FhirPatch {
 	}
 
 	private IBase massageValueForDiff(IBase theNewValue) {
+		IBase massagedValue = theNewValue;
+
 		// XHTML content is dealt with by putting it in a string
 		if (theNewValue instanceof XhtmlNode) {
 			String xhtmlString = ((XhtmlNode) theNewValue).getValueAsString();
-			theNewValue = myContext.getElementDefinition("string").newInstance(xhtmlString);
+			massagedValue = myContext.getElementDefinition("string").newInstance(xhtmlString);
 		}
 
 		// IIdType can hold a fully qualified ID, but we just want the ID part to show up in diffs
 		if (theNewValue instanceof IIdType) {
 			String idPart = ((IIdType) theNewValue).getIdPart();
-			theNewValue = myContext.getElementDefinition("id").newInstance(idPart);
+			massagedValue = myContext.getElementDefinition("id").newInstance(idPart);
 		}
 
-		return theNewValue;
+		return massagedValue;
 	}
 
 	private String toValue(IPrimitiveType<?> theOldPrimitive) {
@@ -490,4 +562,22 @@ public class FhirPatch {
 		}
 		return theOldPrimitive.getValueAsString();
 	}
+
+	private static class ChildDefinition {
+		private final BaseRuntimeChildDefinition myChildDef;
+		private final BaseRuntimeElementDefinition<?> myChildElement;
+
+		public ChildDefinition(BaseRuntimeChildDefinition theChildDef, BaseRuntimeElementDefinition<?> theChildElement) {
+			this.myChildDef = theChildDef;
+			this.myChildElement = theChildElement;
+		}
+
+		public BaseRuntimeChildDefinition getChildDef() {
+			return myChildDef;
+		}
+
+		public BaseRuntimeElementDefinition<?> getChildElement() {
+			return myChildElement;
+		}
+	}
 }