DATAMONGO-2320 - Simplify test code.

Original pull request: #776.

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/aggregation/FilterExpressionUnitTests.java

@@ -61,13 +61,7 @@ public class FilterExpressionUnitTests {
 						.and(filter("items").as("item").by(AggregationFunctionExpressions.GTE.of(Fields.field("item.price"), 100)))
 						.as("items"));
 
-		Document dbo = agg.toDocument("sales", aggregationContext);
-
-		List<Object> pipeline = DocumentTestUtils.getAsDBList(dbo, "pipeline");
-		Document $project = DocumentTestUtils.getAsDocument((Document) pipeline.get(0), "$project");
-		Document items = DocumentTestUtils.getAsDocument($project, "items");
-		Document $filter = DocumentTestUtils.getAsDocument(items, "$filter");
-
+		Document $filter = extractFilterOperatorFromDocument(agg.toDocument("sales", aggregationContext));
 		Document expected = Document.parse("{" + //
 				"input: \"$items\"," + //
 				"as: \"item\"," + //
@@ -83,13 +77,7 @@ public class FilterExpressionUnitTests {
 		TypedAggregation<Sales> agg = Aggregation.newAggregation(Sales.class, Aggregation.project().and("items")
 				.filter("item", AggregationFunctionExpressions.GTE.of(Fields.field("item.price"), 100)).as("items"));
 
-		Document dbo = agg.toDocument("sales", aggregationContext);
-
-		List<Object> pipeline = DocumentTestUtils.getAsDBList(dbo, "pipeline");
-		Document $project = DocumentTestUtils.getAsDocument((Document) pipeline.get(0), "$project");
-		Document items = DocumentTestUtils.getAsDocument($project, "items");
-		Document $filter = DocumentTestUtils.getAsDocument(items, "$filter");
-
+		Document $filter = extractFilterOperatorFromDocument(agg.toDocument("sales", aggregationContext));
 		Document expected = Document.parse("{" + //
 				"input: \"$items\"," + //
 				"as: \"item\"," + //
@@ -106,13 +94,7 @@ public class FilterExpressionUnitTests {
 				Aggregation.project().and(filter(Arrays.<Object> asList(1, "a", 2, null, 3.1D, 4, "5")).as("num")
 						.by(AggregationFunctionExpressions.GTE.of(Fields.field("num"), 3))).as("items"));
 
-		Document dbo = agg.toDocument("sales", aggregationContext);
-
-		List<Object> pipeline = DocumentTestUtils.getAsDBList(dbo, "pipeline");
-		Document $project = DocumentTestUtils.getAsDocument((Document) pipeline.get(0), "$project");
-		Document items = DocumentTestUtils.getAsDocument($project, "items");
-		Document $filter = DocumentTestUtils.getAsDocument(items, "$filter");
-
+		Document $filter = extractFilterOperatorFromDocument(agg.toDocument("sales", aggregationContext));
 		Document expected = Document.parse("{" + //
 				"input: [ 1, \"a\", 2, null, 3.1, 4, \"5\" ]," + //
 				"as: \"num\"," + //
@@ -129,13 +111,7 @@ public class FilterExpressionUnitTests {
 				.and(filter("items").as("item").by(ComparisonOperators.valueOf("item.price").greaterThan("field-1")))
 				.as("items"));
 
-		Document dbo = agg.toDocument("sales", Aggregation.DEFAULT_CONTEXT);
-
-		List<Object> pipeline = DocumentTestUtils.getAsDBList(dbo, "pipeline");
-		Document $project = DocumentTestUtils.getAsDocument((Document) pipeline.get(0), "$project");
-		Document items = DocumentTestUtils.getAsDocument($project, "items");
-		Document $filter = DocumentTestUtils.getAsDocument(items, "$filter");
-
+		Document $filter = extractFilterOperatorFromDocument(agg.toDocument("sales", Aggregation.DEFAULT_CONTEXT));
 		Document expected = Document.parse("{" + //
 				"input: \"$items\"," + //
 				"as: \"item\"," + //
@@ -145,6 +121,14 @@ public class FilterExpressionUnitTests {
 		assertThat($filter).isEqualTo(new Document(expected));
 	}
 
+	private Document extractFilterOperatorFromDocument(Document source) {
+
+		List<Object> pipeline = DocumentTestUtils.getAsDBList(source, "pipeline");
+		Document $project = DocumentTestUtils.getAsDocument((Document) pipeline.get(0), "$project");
+		Document items = DocumentTestUtils.getAsDocument($project, "items");
+		return DocumentTestUtils.getAsDocument(items, "$filter");
+	}
+
 	static class Sales {
 
 		List<Object> items;