Update test expectations

Author: alex-spies

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/optimizer/rules/logical/local/ReplaceMissingFieldWithNull.java

@@ -67,7 +67,7 @@ private LogicalPlan missingToNull(LogicalPlan plan, Predicate<FieldAttribute> sh
             // Project[field1, field2, field3] <- keeps the ordering intact
             // \_Eval[field1 = null, field3 = null]
             // \_EsRelation[field2]
-            // TODO: Test when there are 0 fields remaining
+            // TODO: Double check that we test when there are 0 fields remaining
             List<Attribute> initialOutput = relation.output();
             List<Attribute> remainingFields = new ArrayList<>(initialOutput.size());
             Map<DataType, Alias> nullLiterals = Maps.newLinkedHashMapWithExpectedSize(DataType.types().size());

x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/optimizer/LocalPhysicalPlanOptimizerTests.java

@@ -38,8 +38,8 @@
 import org.elasticsearch.xpack.esql.analysis.Verifier;
 import org.elasticsearch.xpack.esql.core.expression.Alias;
 import org.elasticsearch.xpack.esql.core.expression.Expressions;
+import org.elasticsearch.xpack.esql.core.expression.FieldAttribute;
 import org.elasticsearch.xpack.esql.core.expression.Literal;
-import org.elasticsearch.xpack.esql.core.expression.ReferenceAttribute;
 import org.elasticsearch.xpack.esql.core.tree.Source;
 import org.elasticsearch.xpack.esql.core.type.DataType;
 import org.elasticsearch.xpack.esql.core.type.EsField;
@@ -1340,9 +1340,9 @@ public void testMissingFieldsDoNotGetExtracted() {
             )
         );
         // emp_no
-        assertThat(projections.get(1), instanceOf(ReferenceAttribute.class));
+        assertThat(projections.get(1), instanceOf(FieldAttribute.class));
         // first_name
-        assertThat(projections.get(2), instanceOf(ReferenceAttribute.class));
+        assertThat(projections.get(2), instanceOf(FieldAttribute.class));
 
         // last_name --> first_name
         var nullAlias = Alias.unwrap(projections.get(8));