DATAMONGO-1141 - Polishing.

Aligned assertion messages for consistency. Fixed imports in  UpdateMapperUnitTests.

Original pull request: #405.

Author: odrotbohm

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/query/Update.java

@@ -316,7 +316,7 @@ public Update currentTimestamp(String key) {
 	 */
 	public Update multiply(String key, Number multiplier) {
 
-		Assert.notNull(multiplier, "Multiplier must not be 'null'.");
+		Assert.notNull(multiplier, "Multiplier must not be null.");
 		addMultiFieldOperation("$mul", key, multiplier.doubleValue());
 		return this;
 	}
@@ -333,7 +333,7 @@ public Update multiply(String key, Number multiplier) {
 	 */
 	public Update max(String key, Object value) {
 
-		Assert.notNull(value, "Value for max operation must not be 'null'.");
+		Assert.notNull(value, "Value for max operation must not be null.");
 		addMultiFieldOperation("$max", key, value);
 		return this;
 	}
@@ -350,7 +350,7 @@ public Update max(String key, Object value) {
 	 */
 	public Update min(String key, Object value) {
 
-		Assert.notNull(value, "Value for min operation must not be 'null'.");
+		Assert.notNull(value, "Value for min operation must not be null.");
 		addMultiFieldOperation("$min", key, value);
 		return this;
 	}
@@ -782,7 +782,7 @@ public PushOperatorBuilder slice(int count) {
 		 */
 		public PushOperatorBuilder sort(Direction direction) {
 
-			Assert.notNull(direction, "Direction must not be 'null'.");
+			Assert.notNull(direction, "Direction must not be null.");
 			this.modifiers.addModifier(new SortModifier(direction));
 			return this;
 		}
@@ -797,7 +797,7 @@ public PushOperatorBuilder sort(Direction direction) {
 		 */
 		public PushOperatorBuilder sort(Sort sort) {
 
-			Assert.notNull(sort, "Sort must not be 'null'.");
+			Assert.notNull(sort, "Sort must not be null.");
 			this.modifiers.addModifier(new SortModifier(sort));
 			return this;
 		}

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/convert/UpdateMapperUnitTests.java

@@ -15,9 +15,7 @@
  */
 package org.springframework.data.mongodb.core.convert;
 
-import static org.hamcrest.CoreMatchers.*;
-import static org.hamcrest.Matchers.equalTo;
-import static org.hamcrest.collection.IsMapContaining.*;
+import static org.hamcrest.Matchers.*;
 import static org.junit.Assert.*;
 import static org.mockito.Mockito.*;
 import static org.springframework.data.mongodb.core.DBObjectTestUtils.*;
@@ -85,6 +83,7 @@ public class UpdateMapperUnitTests {
 	private Converter<NestedEntity, DBObject> writingConverterSpy;
 
 	@Before
+	@SuppressWarnings("unchecked")
 	public void setUp() {
 
 		this.writingConverterSpy = Mockito.spy(new NestedEntityWriteConverter());