Create unit test for NativeSearchQueryBuilder

- add validate conditions in searchAfter()
  - cause SearchAfterBuilder.setSortValues() assert not allow empty values
- delete not appropriate tests for searchAfter in SearchAfterIntegrationTests

Author: owen-qq

src/main/java/org/springframework/data/elasticsearch/core/query/NativeSearchQueryBuilder.java

@@ -345,6 +345,10 @@ public NativeSearchQueryBuilder withSuggestBuilder(SuggestBuilder suggestBuilder
 	}
 
 	public NativeSearchQueryBuilder withSearchAfter(List<Object> searchAfter) {
+		if (searchAfter != null && searchAfter.isEmpty()) {
+			return this;
+		}
+
 		this.searchAfter = searchAfter;
 		return this;
 	}

src/test/java/org/springframework/data/elasticsearch/core/paginating/SearchAfterIntegrationTests.java

@@ -15,16 +15,13 @@
  */
 package org.springframework.data.elasticsearch.core.paginating;
 
-import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.fail;
+import static org.assertj.core.api.Assertions.*;
 
 import java.util.ArrayList;
 import java.util.List;
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 
-import org.elasticsearch.search.sort.SortBuilders;
-import org.elasticsearch.search.sort.SortOrder;
 import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Test;
 import org.springframework.beans.factory.annotation.Autowired;
@@ -36,7 +33,6 @@
 import org.springframework.data.elasticsearch.annotations.FieldType;
 import org.springframework.data.elasticsearch.core.ElasticsearchOperations;
 import org.springframework.data.elasticsearch.core.SearchHits;
-import org.springframework.data.elasticsearch.core.query.NativeSearchQueryBuilder;
 import org.springframework.data.elasticsearch.core.query.Query;
 import org.springframework.data.elasticsearch.junit.jupiter.SpringIntegrationTest;
 import org.springframework.lang.Nullable;
@@ -83,41 +79,6 @@ void shouldReadPagesWithSearchAfter() {
 		assertThat(foundEntities).containsExactlyElementsOf(entities);
 	}
 
-	@Test // #2105
-	@DisplayName("should read pages with search_after using native search query")
-	void shouldReadPagesWithSearchAfterUsingNativeSearchQuery() {
-
-		List<Entity> entities = IntStream.rangeClosed(1, 10).mapToObj(i -> new Entity((long) i, "message " + i))
-										 .collect(Collectors.toList());
-		operations.save(entities);
-
-		NativeSearchQueryBuilder nativeSearchQueryBuilder = new NativeSearchQueryBuilder();
-
-		nativeSearchQueryBuilder.withPageable(PageRequest.of(0, 3));
-		nativeSearchQueryBuilder.withSorts(SortBuilders.fieldSort("id").order(SortOrder.ASC));
-
-		List<Object> searchAfter = null;
-		List<Entity> foundEntities = new ArrayList<>();
-
-		int loop = 0;
-		do {
-			nativeSearchQueryBuilder.withSearchAfter(searchAfter);
-			SearchHits<Entity> searchHits = operations.search(nativeSearchQueryBuilder.build(), Entity.class);
-
-			if (searchHits.getSearchHits().size() == 0) {
-				break;
-			}
-			foundEntities.addAll(searchHits.stream().map(searchHit -> searchHit.getContent()).collect(Collectors.toList()));
-			searchAfter = searchHits.getSearchHit((int) (searchHits.getSearchHits().size() - 1)).getSortValues();
-
-			if (++loop > 10) {
-				fail("loop not terminating");
-			}
-		} while (true);
-
-		assertThat(foundEntities).containsExactlyElementsOf(entities);
-	}
-
 	@Document(indexName = "test-search-after")
 	private static class Entity {
 		@Nullable

src/test/java/org/springframework/data/elasticsearch/core/query/NativeSearchQueryBuilderTests.java

@@ -0,0 +1,47 @@
+package org.springframework.data.elasticsearch.core.query;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.List;
+
+import org.junit.jupiter.api.Test;
+
+import com.google.common.collect.Lists;
+
+/**
+ * @author owen.qq
+ */
+public class NativeSearchQueryBuilderTests {
+
+    @Test // #2105
+    void shouldContainEffectiveSearchAfterValue() {
+        Long lastSortValue = 1L;
+        List<Object> searchAfter = Lists.newArrayList(lastSortValue);
+
+        NativeSearchQueryBuilder nativeSearchQueryBuilder = new NativeSearchQueryBuilder();
+        nativeSearchQueryBuilder.withSearchAfter(searchAfter);
+        NativeSearchQuery nativeSearchQuery = nativeSearchQueryBuilder.build();
+
+        assertThat(nativeSearchQuery.getSearchAfter()).isNotNull();
+    }
+
+    @Test // #2105
+    void shouldIgnoreNullableSearchAfterValue() {
+        List<Object> emptySearchValueByFirstSearch = null;
+        NativeSearchQueryBuilder nativeSearchQueryBuilder = new NativeSearchQueryBuilder();
+        nativeSearchQueryBuilder.withSearchAfter(emptySearchValueByFirstSearch);
+        NativeSearchQuery nativeSearchQuery = nativeSearchQueryBuilder.build();
+
+        assertThat(nativeSearchQuery.getSearchAfter()).isNull();
+    }
+
+    @Test // #2105
+    void shouldIgnoreEmptySearchAfterValue() {
+        List<Object> emptySearchValueByFirstSearch = Lists.newArrayList();
+        NativeSearchQueryBuilder nativeSearchQueryBuilder = new NativeSearchQueryBuilder();
+        nativeSearchQueryBuilder.withSearchAfter(emptySearchValueByFirstSearch);
+        NativeSearchQuery nativeSearchQuery = nativeSearchQueryBuilder.build();
+
+        assertThat(nativeSearchQuery.getSearchAfter()).isNull();
+    }
+}