Fix flaky test method writesAndReadsCustomFieldsConvertedClass.

src/main/java/org/springframework/data/couchbase/core/mapping/CouchbaseDocument.java

@@ -18,14 +18,14 @@
 
 import com.couchbase.client.java.json.JsonObject;
 
-import java.util.HashMap;
+import java.util.TreeMap;
 import java.util.Map;
 
 /**
  * A {@link CouchbaseDocument} is an abstract representation of a document stored inside Couchbase Server.
  * <p/>
  * <p>
- * It acts like a {@link HashMap}, but only allows those types to be written that are supported by the underlying
+ * It acts like a {@link TreeMap}, but only allows those types to be written that are supported by the underlying
  * storage format, which is currently JSON. Note that JSON conversion is not happening here, but performed at a
  * different stage based on the payload stored in the {@link CouchbaseDocument}.
  * </p>
@@ -85,7 +85,7 @@ public CouchbaseDocument(final String id) {
 	public CouchbaseDocument(final String id, final int expiration) {
 		this.id = id;
 		this.expiration = expiration;
-		content = new HashMap<>();
+		content = new TreeMap<>();
 	}
 
 	/**
@@ -119,8 +119,8 @@ public final Object get(final String key) {
 	 *
 	 * @return
 	 */
-	public final HashMap<String, Object> export() {
-		HashMap<String, Object> toExport = new HashMap<String, Object>(content);
+	public final TreeMap<String, Object> export() {
+		TreeMap<String, Object> toExport = new TreeMap<String, Object>(content);
 		for (Map.Entry<String, Object> entry : content.entrySet()) {
 			if (entry.getValue() instanceof CouchbaseDocument) {
 				toExport.put(entry.getKey(), ((CouchbaseDocument) entry.getValue()).export());

src/test/java/org/springframework/data/couchbase/core/mapping/MappingCouchbaseConverterTests.java

@@ -455,7 +455,7 @@ void writesAndReadsCustomConvertedClass() {
 		List<BigDecimal> listOfValues = new ArrayList<>();
 		listOfValues.add(value);
 		listOfValues.add(value2);
-		Map<String, BigDecimal> mapOfValues = new HashMap<>();
+		Map<String, BigDecimal> mapOfValues = new TreeMap<>();
 		mapOfValues.put("val1", value);
 		mapOfValues.put("val2", value2);