NIAD-3222: GP2GP adaptor generates an empty CompoundStatement/code which fails the transfer.

Replace String.Empty when preparing the code element mapping ObservationMapper so that an EhrMapperException is thrown containing the resource identifier.
Add test to ensure this exception is found and contains the resource id.
Update NOPAT test and associated resource file which previously did not contain a code element
Update CHANGELOG.md

Author: MartinWheelerMT

CHANGELOG.md

@@ -8,6 +8,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Fixed
 
+* When mapping an `Observation` related to a diagnostic report which does not contain a `code` element, the adaptor will
+  now throw an error reporting that an observation requires a code element and provide the affected resource ID.
 * When mapping a `valueQuantity` contained in an `Observation`, the produced XML `<value>` element now correctly escapes
   any contained XML characters.
 

service/src/main/java/uk/nhs/adaptors/gp2gp/ehr/mapper/diagnosticreport/ObservationMapper.java

@@ -488,7 +488,7 @@ private String prepareCodeElement(Observation observation) {
             return codeableConceptCdMapper.mapCodeableConceptToCd(observation.getCode());
         }
 
-        return StringUtils.EMPTY;
+        throw new EhrMapperException("%s must contain a code element.".formatted(observation.getId()));
     }
 
     private CompoundStatementClassCode prepareClassCode(List<MultiStatementObservationHolder> derivedObservations) {

service/src/test/java/uk/nhs/adaptors/gp2gp/ehr/mapper/diagnosticreport/ObservationMapperTest.java

@@ -21,6 +21,7 @@
 import uk.nhs.adaptors.gp2gp.common.service.ConfidentialityService;
 import uk.nhs.adaptors.gp2gp.common.service.FhirParseService;
 import uk.nhs.adaptors.gp2gp.common.service.RandomIdGeneratorService;
+import uk.nhs.adaptors.gp2gp.ehr.exception.EhrMapperException;
 import uk.nhs.adaptors.gp2gp.ehr.mapper.AgentDirectory;
 import uk.nhs.adaptors.gp2gp.ehr.mapper.CodeableConceptCdMapper;
 import uk.nhs.adaptors.gp2gp.ehr.mapper.IdMapper;
@@ -36,6 +37,7 @@
 import java.util.stream.Stream;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
 import static org.junit.jupiter.api.Assertions.assertAll;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.Mockito.lenient;
@@ -218,10 +220,21 @@ void When_MappingTestGroupHeader_With_NopatMetaSecurity_Expect_ConfidentialityCo
 
         assertAll(
             () -> assertThatXml(actualXml).containsXPath(COMPOUND_STATEMENT_CONFIDENTIALITY_CODE_XPATH),
-            () -> assertThat(metaWithNopat).hasSize(1)
+            () -> assertThat(metaWithNopat).hasSize(2)
         );
     }
 
+    @Test
+    void When_MappingTestGroupHeader_WithoutCode_Expect_ExceptionThrownContainingId() {
+        final Observation observation = getObservationResourceFromJson(OBSERVATION_TEST_GROUP_HEADER_JSON);
+        observation.setCode(null);
+
+        assertThatExceptionOfType(EhrMapperException.class)
+            .isThrownBy(() -> observationMapper.mapObservationToCompoundStatement(observation))
+            .withMessageContaining(observation.getId());
+
+    }
+
     @Test
     void When_MappingTestGroupHeader_With_NoscrubMetaSecurity_Expect_ConfidentialityCodeNotPresent() {
         final Observation observation = getObservationResourceFromJson(OBSERVATION_TEST_GROUP_HEADER_JSON);

service/src/test/resources/ehr/mapper/diagnosticreport/observation/observation_test_group_header.json

@@ -6,6 +6,15 @@
       "https://fhir.nhs.uk/STU3/StructureDefinition/CareConnect-GPC-Observation-1"
     ]
   },
+  "code": {
+    "coding": [
+      {
+        "system": "http://snomed.info/sct",
+        "code": "242247008",
+        "display": "Collision of spacecraft with meteorite"
+      }
+    ]
+  },
   "identifier": [
     {
       "system": "https://EMISWeb/A82038",