Polishing.

Add author tags, tweak Javadoc style. Simplify tests. Document operator.

See #3724
Original pull request: #3759.

Author: mp911de

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/ArithmeticOperators.java

@@ -40,6 +40,7 @@
  *
  * @author Christoph Strobl
  * @author Mark Paluch
+ * @author Mushtaq Ahmed
  * @since 1.10
  */
 public class ArithmeticOperators {
@@ -65,7 +66,8 @@ public static ArithmeticOperatorFactory valueOf(AggregationExpression expression
 	}
 
 	/**
-	 * Creates new {@link AggregationExpression} that returns a random float between 0 and 1 each time it is called.
+	 * Creates new {@link AggregationExpression} that returns a random float between {@code 0} and {@code 1} each time it
+	 * is called.
 	 *
 	 * @return new instance of {@link Rand}.
 	 * @since 3.3

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

@@ -29,6 +29,7 @@
  *
  * @author Christoph Strobl
  * @author Mark Paluch
+ * @author Mushtaq Ahmed
  */
 class ArithmeticOperatorsUnitTests {
 
@@ -166,9 +167,8 @@ void rendersTanhWithValueInDegrees() {
 				.isEqualTo("{ $tanh : { $degreesToRadians : \"$angle\" } }");
 	}
 
-
 	@Test // GH-3724
-	void rendersRank() {
+	void rendersRand() {
 		assertThat(rand().toDocument(Aggregation.DEFAULT_CONTEXT)).isEqualTo(new Document("$rand", new Document()));
 	}
 }

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

@@ -1036,17 +1036,19 @@ void shouldRenderTanh() {
 
 	@Test // GH-3713
 	void shouldRenderDateAdd() {
-		assertThat(transform("dateAdd(purchaseDate, 'day', 3)")).isEqualTo(Document.parse("{ $dateAdd: { startDate: \"$purchaseDate\", unit: \"day\", amount: 3 } }"));
+		assertThat(transform("dateAdd(purchaseDate, 'day', 3)"))
+				.isEqualTo("{ $dateAdd: { startDate: \"$purchaseDate\", unit: \"day\", amount: 3 } }");
 	}
 
 	@Test // GH-3713
 	void shouldRenderDateDiff() {
-		assertThat(transform("dateDiff(purchaseDate, delivered, 'day')")).isEqualTo(Document.parse("{ $dateDiff: { startDate: \"$purchaseDate\", endDate: \"$delivered\", unit: \"day\" } }"));
+		assertThat(transform("dateDiff(purchaseDate, delivered, 'day')"))
+				.isEqualTo("{ $dateDiff: { startDate: \"$purchaseDate\", endDate: \"$delivered\", unit: \"day\" } }");
 	}
 
 	@Test // GH-3724
 	void shouldRenderRand() {
-		assertThat(transform("rand()")).isEqualTo(Document.parse("{ $rand : {} }"));
+		assertThat(transform("rand()")).isEqualTo("{ $rand : {} }");
 	}
 
 	private Document transform(String expression, Object... params) {

src/main/asciidoc/reference/aggregation-framework.adoc

@@ -76,7 +76,7 @@ At the time of this writing, we provide support for the following Aggregation Op
 [cols="2*"]
 |===
 | Pipeline Aggregation Operators
-| `bucket`, `bucketAuto`, `count`, `facet`, `geoNear`, `graphLookup`, `group`, `limit`, `lookup`, `match`, `project`, `replaceRoot`, `skip`, `sort`, `unwind`
+| `bucket`, `bucketAuto`, `count`, `facet`, `geoNear`, `graphLookup`, `group`, `limit`, `lookup`, `match`, `project`, `rand`, `replaceRoot`, `skip`, `sort`, `unwind`
 
 | Set Aggregation Operators
 | `setEquals`, `setIntersection`, `setUnion`, `setDifference`, `setIsSubset`, `anyElementTrue`, `allElementsTrue`