diff --git a/src/main/java/org/springframework/data/jpa/repository/cdi/JpaRepositoryBean.java b/src/main/java/org/springframework/data/jpa/repository/cdi/JpaRepositoryBean.java
index e5f7695f2..f4079977f 100644
--- a/src/main/java/org/springframework/data/jpa/repository/cdi/JpaRepositoryBean.java
+++ b/src/main/java/org/springframework/data/jpa/repository/cdi/JpaRepositoryBean.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2011 the original author or authors.
+ * Copyright 2011-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -25,7 +25,7 @@ import javax.persistence.EntityManager;
 
 import org.springframework.data.jpa.repository.support.JpaRepositoryFactory;
 import org.springframework.data.repository.cdi.CdiRepositoryBean;
-import org.springframework.data.repository.config.CustomRepositoryImplementationDetector;
+import org.springframework.data.repository.config.CustomRepositoryImplementationDetector;
 import org.springframework.util.Assert;
 
 /**
@@ -47,14 +47,14 @@ class JpaRepositoryBean<T> extends CdiRepositoryBean<T> {
 	 * @param entityManagerBean must not be {@literal null}.
 	 * @param qualifiers must not be {@literal null}.
 	 * @param repositoryType must not be {@literal null}.
-	 * @param detector can be {@literal null}.
+	 * @param detector can be {@literal null}.
 	 */
 	JpaRepositoryBean(BeanManager beanManager, Bean<EntityManager> entityManagerBean, Set<Annotation> qualifiers,
-			Class<T> repositoryType, CustomRepositoryImplementationDetector detector) {
+			Class<T> repositoryType, CustomRepositoryImplementationDetector detector) {
 
-		super(qualifiers, repositoryType, beanManager, detector);
+		super(qualifiers, repositoryType, beanManager, detector);
 
-		Assert.notNull(entityManagerBean);
+		Assert.notNull(entityManagerBean, "EntityManager bean must not be null!");
 		this.entityManagerBean = entityManagerBean;
 	}
 
diff --git a/src/main/java/org/springframework/data/jpa/repository/query/AbstractJpaQuery.java b/src/main/java/org/springframework/data/jpa/repository/query/AbstractJpaQuery.java
index 954e9fa53..2006f12d0 100644
--- a/src/main/java/org/springframework/data/jpa/repository/query/AbstractJpaQuery.java
+++ b/src/main/java/org/springframework/data/jpa/repository/query/AbstractJpaQuery.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2008-2016 the original author or authors.
+ * Copyright 2008-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -48,6 +48,7 @@ import org.springframework.util.Assert;
  * 
  * @author Oliver Gierke
  * @author Thomas Darimont
+ * @author Mark Paluch
  */
 public abstract class AbstractJpaQuery implements RepositoryQuery {
 
@@ -59,13 +60,12 @@ public abstract class AbstractJpaQuery implements RepositoryQuery {
 	 * Creates a new {@link AbstractJpaQuery} from the given {@link JpaQueryMethod}.
 	 * 
 	 * @param method
-	 * @param resultFactory
 	 * @param em
 	 */
 	public AbstractJpaQuery(JpaQueryMethod method, EntityManager em) {
 
-		Assert.notNull(method);
-		Assert.notNull(em);
+		Assert.notNull(method, "JpaQueryMethod must not be null!");
+		Assert.notNull(em, "EntityManager must not be null!");
 
 		this.method = method;
 		this.em = em;
diff --git a/src/main/java/org/springframework/data/jpa/repository/query/CriteriaQueryParameterBinder.java b/src/main/java/org/springframework/data/jpa/repository/query/CriteriaQueryParameterBinder.java
index 3955ab605..9b192e718 100644
--- a/src/main/java/org/springframework/data/jpa/repository/query/CriteriaQueryParameterBinder.java
+++ b/src/main/java/org/springframework/data/jpa/repository/query/CriteriaQueryParameterBinder.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2011-2013 the original author or authors.
+ * Copyright 2011-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -32,6 +32,7 @@ import org.springframework.util.Assert;
  * 
  * @author Oliver Gierke
  * @author Thomas Darimont
+ * @author Mark Paluch
  */
 class CriteriaQueryParameterBinder extends ParameterBinder {
 
@@ -41,14 +42,15 @@ class CriteriaQueryParameterBinder extends ParameterBinder {
 	 * Creates a new {@link CriteriaQueryParameterBinder} for the given {@link Parameters}, values and some
 	 * {@link javax.persistence.criteria.ParameterExpression}.
 	 * 
-	 * @param parameters
-	 * @param values
-	 * @param expressions
+	 * @param parameters must not be {@literal null}.
+	 * @param values must not be {@literal null}.
+	 * @param expressions must not be {@literal null}.
 	 */
 	CriteriaQueryParameterBinder(JpaParameters parameters, Object[] values, Iterable<ParameterMetadata<?>> expressions) {
 
 		super(parameters, values);
-		Assert.notNull(expressions);
+
+		Assert.notNull(expressions, "Iterable of ParameterMetadata must not be null!");
 		this.expressions = expressions.iterator();
 	}
 
diff --git a/src/main/java/org/springframework/data/jpa/repository/query/JpaQueryCreator.java b/src/main/java/org/springframework/data/jpa/repository/query/JpaQueryCreator.java
index 6b64b85d8..81fb0d0ab 100644
--- a/src/main/java/org/springframework/data/jpa/repository/query/JpaQueryCreator.java
+++ b/src/main/java/org/springframework/data/jpa/repository/query/JpaQueryCreator.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2008-2015 the original author or authors.
+ * Copyright 2008-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -202,8 +202,8 @@ public class JpaQueryCreator extends AbstractQueryCreator<CriteriaQuery<? extend
 		 */
 		public PredicateBuilder(Part part, Root<?> root) {
 
-			Assert.notNull(part);
-			Assert.notNull(root);
+			Assert.notNull(part, "Part must not be null!");
+			Assert.notNull(root, "Root must not be null!");
 			this.part = part;
 			this.root = root;
 		}
diff --git a/src/main/java/org/springframework/data/jpa/repository/query/JpaQueryExecution.java b/src/main/java/org/springframework/data/jpa/repository/query/JpaQueryExecution.java
index 0fd17468f..f198e94fc 100644
--- a/src/main/java/org/springframework/data/jpa/repository/query/JpaQueryExecution.java
+++ b/src/main/java/org/springframework/data/jpa/repository/query/JpaQueryExecution.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2008-2015 the original author or authors.
+ * Copyright 2008-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -68,13 +68,13 @@ public abstract class JpaQueryExecution {
 	 * Executes the given {@link AbstractStringBasedJpaQuery} with the given {@link ParameterBinder}.
 	 * 
 	 * @param query must not be {@literal null}.
-	 * @param binder must not be {@literal null}.
+	 * @param values must not be {@literal null}.
 	 * @return
 	 */
 	public Object execute(AbstractJpaQuery query, Object[] values) {
 
-		Assert.notNull(query);
-		Assert.notNull(values);
+		Assert.notNull(query, "AbstractJpaQuery must not be null!");
+		Assert.notNull(values, "Values must not be null!");
 
 		Object result;
 
diff --git a/src/main/java/org/springframework/data/jpa/repository/query/ParameterBinder.java b/src/main/java/org/springframework/data/jpa/repository/query/ParameterBinder.java
index f78ff8847..73dee3da8 100644
--- a/src/main/java/org/springframework/data/jpa/repository/query/ParameterBinder.java
+++ b/src/main/java/org/springframework/data/jpa/repository/query/ParameterBinder.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2008-2014 the original author or authors.
+ * Copyright 2008-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -33,6 +33,7 @@ import org.springframework.util.Assert;
  * 
  * @author Oliver Gierke
  * @author Thomas Darimont
+ * @author Mark Paluch
  */
 public class ParameterBinder {
 
@@ -48,8 +49,8 @@ public class ParameterBinder {
 	 */
 	public ParameterBinder(JpaParameters parameters, Object[] values) {
 
-		Assert.notNull(parameters);
-		Assert.notNull(values);
+		Assert.notNull(parameters, "JpaParameters must not be null!");
+		Assert.notNull(values, "Values must not be null!");
 
 		Assert.isTrue(parameters.getNumberOfParameters() == values.length, "Invalid number of parameters given!");
 
diff --git a/src/main/java/org/springframework/data/jpa/repository/query/ParameterMetadataProvider.java b/src/main/java/org/springframework/data/jpa/repository/query/ParameterMetadataProvider.java
index 9d101d26a..781db7462 100644
--- a/src/main/java/org/springframework/data/jpa/repository/query/ParameterMetadataProvider.java
+++ b/src/main/java/org/springframework/data/jpa/repository/query/ParameterMetadataProvider.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2011-2016 the original author or authors.
+ * Copyright 2011-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -41,6 +41,7 @@ import org.springframework.util.ObjectUtils;
  * 
  * @author Oliver Gierke
  * @author Thomas Darimont
+ * @author Mark Paluch
  */
 class ParameterMetadataProvider {
 
@@ -144,12 +145,12 @@ class ParameterMetadataProvider {
 	 * @param <T>
 	 * @param part must not be {@literal null}.
 	 * @param type must not be {@literal null}.
-	 * @param name
+	 * @param parameter
 	 * @return
 	 */
 	private <T> ParameterMetadata<T> next(Part part, Class<T> type, Parameter parameter) {
 
-		Assert.notNull(type);
+		Assert.notNull(type, "Type must not be null!");
 
 		/*
 		 * We treat Expression types as Object vales since the real value to be bound as a parameter is determined at query time.
@@ -221,7 +222,7 @@ class ParameterMetadataProvider {
 		 */
 		public Object prepare(Object value) {
 
-			Assert.notNull(value);
+			Assert.notNull(value, "Value must not be null!");
 
 			Class<? extends T> expressionType = expression.getJavaType();
 
diff --git a/src/main/java/org/springframework/data/jpa/repository/query/QueryUtils.java b/src/main/java/org/springframework/data/jpa/repository/query/QueryUtils.java
index 060f85cae..6ae1452d0 100644
--- a/src/main/java/org/springframework/data/jpa/repository/query/QueryUtils.java
+++ b/src/main/java/org/springframework/data/jpa/repository/query/QueryUtils.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2008-2016 the original author or authors.
+ * Copyright 2008-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -69,6 +69,7 @@ import org.springframework.util.StringUtils;
  * @author Thomas Darimont
  * @author Komi Innocent
  * @author Christoph Strobl
+ * @author Mark Paluch
  */
 public abstract class QueryUtils {
 
@@ -221,14 +222,14 @@ public abstract class QueryUtils {
 	/**
 	 * Adds {@literal order by} clause to the JPQL query.
 	 * 
-	 * @param query
+	 * @param query must not be {@literal null} or empty.
 	 * @param sort
 	 * @param alias
 	 * @return
 	 */
 	public static String applySorting(String query, Sort sort, String alias) {
 
-		Assert.hasText(query);
+		Assert.hasText(query, "Query must not be null or empty!");
 
 		if (null == sort || !sort.iterator().hasNext()) {
 			return query;
@@ -356,16 +357,16 @@ public abstract class QueryUtils {
 	 * entities to the query.
 	 * 
 	 * @param <T>
-	 * @param queryString
-	 * @param entities
-	 * @param entityManager
+	 * @param queryString must not be {@literal null}.
+	 * @param entities must not be {@literal null}.
+	 * @param entityManager must not be {@literal null}.
 	 * @return
 	 */
 	public static <T> Query applyAndBind(String queryString, Iterable<T> entities, EntityManager entityManager) {
 
-		Assert.notNull(queryString);
-		Assert.notNull(entities);
-		Assert.notNull(entityManager);
+		Assert.notNull(queryString, "Querystring must not be null!");
+		Assert.notNull(entities, "Iterable of entities must not be null!");
+		Assert.notNull(entityManager, "EntityManager must not be null!");
 
 		Iterator<T> iterator = entities.iterator();
 
@@ -489,8 +490,8 @@ public abstract class QueryUtils {
 			return orders;
 		}
 
-		Assert.notNull(root);
-		Assert.notNull(cb);
+		Assert.notNull(root, "Root must not be null!");
+		Assert.notNull(cb, "CriteriaBuilder must not be null!");
 
 		for (org.springframework.data.domain.Sort.Order order : sort) {
 			orders.add(toJpaOrder(order, root, cb));
diff --git a/src/main/java/org/springframework/data/jpa/repository/query/StringQuery.java b/src/main/java/org/springframework/data/jpa/repository/query/StringQuery.java
index bc713ae95..1f612e45a 100644
--- a/src/main/java/org/springframework/data/jpa/repository/query/StringQuery.java
+++ b/src/main/java/org/springframework/data/jpa/repository/query/StringQuery.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2013-2016 the original author or authors.
+ * Copyright 2013-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -37,6 +37,7 @@ import org.springframework.util.StringUtils;
  * @author Oliver Gierke
  * @author Thomas Darimont
  * @author Oliver Wehrens
+ * @author Mark Paluch
  */
 class StringQuery {
 
@@ -729,7 +730,7 @@ class StringQuery {
 		 */
 		private static Type getLikeTypeFrom(String expression) {
 
-			Assert.hasText(expression);
+			Assert.hasText(expression, "Expression must not be null or empty!");
 
 			if (expression.matches("%.*%")) {
 				return Type.CONTAINING;
diff --git a/src/main/java/org/springframework/data/jpa/repository/support/JpaEntityInformationSupport.java b/src/main/java/org/springframework/data/jpa/repository/support/JpaEntityInformationSupport.java
index 92d325f1f..959128a16 100644
--- a/src/main/java/org/springframework/data/jpa/repository/support/JpaEntityInformationSupport.java
+++ b/src/main/java/org/springframework/data/jpa/repository/support/JpaEntityInformationSupport.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2011 the original author or authors.
+ * Copyright 2011-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -30,6 +30,7 @@ import org.springframework.util.Assert;
  * Base class for {@link JpaEntityInformation} implementations to share common method implementations.
  * 
  * @author Oliver Gierke
+ * @author Mark Paluch
  */
 public abstract class JpaEntityInformationSupport<T, ID extends Serializable> extends AbstractEntityInformation<T, ID>
 		implements JpaEntityInformation<T, ID> {
@@ -56,8 +57,8 @@ public abstract class JpaEntityInformationSupport<T, ID extends Serializable> ex
 	@SuppressWarnings({ "rawtypes", "unchecked" })
 	public static <T> JpaEntityInformation<T, ?> getEntityInformation(Class<T> domainClass, EntityManager em) {
 
-		Assert.notNull(domainClass);
-		Assert.notNull(em);
+		Assert.notNull(domainClass, "Domain class must not be null!");
+		Assert.notNull(em, "EntityManager must not be null!");
 
 		Metamodel metamodel = em.getMetamodel();
 
diff --git a/src/main/java/org/springframework/data/jpa/repository/support/JpaMetamodelEntityInformation.java b/src/main/java/org/springframework/data/jpa/repository/support/JpaMetamodelEntityInformation.java
index c92c61d48..22b693c96 100644
--- a/src/main/java/org/springframework/data/jpa/repository/support/JpaMetamodelEntityInformation.java
+++ b/src/main/java/org/springframework/data/jpa/repository/support/JpaMetamodelEntityInformation.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2011-2016 the original author or authors.
+ * Copyright 2011-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -64,7 +64,7 @@ public class JpaMetamodelEntityInformation<T, ID extends Serializable> extends J
 
 		super(domainClass);
 
-		Assert.notNull(metamodel);
+		Assert.notNull(metamodel, "Metamodel must not be null!");
 		this.metamodel = metamodel;
 
 		ManagedType<T> type = metamodel.managedType(domainClass);
@@ -210,7 +210,9 @@ public class JpaMetamodelEntityInformation<T, ID extends Serializable> extends J
 	 * @see org.springframework.data.jpa.repository.support.JpaEntityInformation#getCompositeIdAttributeValue(java.io.Serializable, java.lang.String)
 	 */
 	public Object getCompositeIdAttributeValue(Serializable id, String idAttribute) {
-		Assert.isTrue(hasCompositeId());
+		
+		Assert.isTrue(hasCompositeId(), "Model must have a composite Id!");
+		
 		return new DirectFieldAccessFallbackBeanWrapper(id).getPropertyValue(idAttribute);
 	}
 
diff --git a/src/main/java/org/springframework/data/jpa/repository/support/JpaRepositoryFactory.java b/src/main/java/org/springframework/data/jpa/repository/support/JpaRepositoryFactory.java
index 01eb14543..a4a2bfa84 100644
--- a/src/main/java/org/springframework/data/jpa/repository/support/JpaRepositoryFactory.java
+++ b/src/main/java/org/springframework/data/jpa/repository/support/JpaRepositoryFactory.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2008-2015 the original author or authors.
+ * Copyright 2008-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -38,6 +38,7 @@ import org.springframework.util.Assert;
  * JPA specific generic repository factory.
  * 
  * @author Oliver Gierke
+ * @author Mark Paluch
  */
 public class JpaRepositoryFactory extends RepositoryFactorySupport {
 
@@ -52,7 +53,7 @@ public class JpaRepositoryFactory extends RepositoryFactorySupport {
 	 */
 	public JpaRepositoryFactory(EntityManager entityManager) {
 
-		Assert.notNull(entityManager);
+		Assert.notNull(entityManager, "EntityManager must not be null!");
 
 		this.entityManager = entityManager;
 		this.extractor = PersistenceProvider.fromEntityManager(entityManager);
diff --git a/src/main/java/org/springframework/data/jpa/repository/support/QueryDslRepositorySupport.java b/src/main/java/org/springframework/data/jpa/repository/support/QueryDslRepositorySupport.java
index 22a4fef89..294a117ad 100644
--- a/src/main/java/org/springframework/data/jpa/repository/support/QueryDslRepositorySupport.java
+++ b/src/main/java/org/springframework/data/jpa/repository/support/QueryDslRepositorySupport.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2011 the original author or authors.
+ * Copyright 2011-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -35,6 +35,7 @@ import com.querydsl.jpa.impl.JPAUpdateClause;
  * Base class for implementing repositories using QueryDsl library.
  * 
  * @author Oliver Gierke
+ * @author Mark Paluch
  */
 @Repository
 public abstract class QueryDslRepositorySupport {
@@ -50,7 +51,8 @@ public abstract class QueryDslRepositorySupport {
 	 * @param domainClass must not be {@literal null}.
 	 */
 	public QueryDslRepositorySupport(Class<?> domainClass) {
-		Assert.notNull(domainClass);
+
+		Assert.notNull(domainClass, "Domain class must not be null!");
 		this.builder = new PathBuilderFactory().create(domainClass);
 	}
 
@@ -62,7 +64,7 @@ public abstract class QueryDslRepositorySupport {
 	@PersistenceContext
 	public void setEntityManager(EntityManager entityManager) {
 
-		Assert.notNull(entityManager);
+		Assert.notNull(entityManager, "EntityManager must not be null!");
 		this.querydsl = new Querydsl(entityManager, builder);
 		this.entityManager = entityManager;
 	}
@@ -88,7 +90,7 @@ public abstract class QueryDslRepositorySupport {
 	/**
 	 * Returns a fresh {@link JPQLQuery}.
 	 * 
-	 * @param path must not be {@literal null}.
+	 * @param paths must not be {@literal null}.
 	 * @return the Querydsl {@link JPQLQuery}.
 	 */
 	protected JPQLQuery<Object> from(EntityPath<?>... paths) {
diff --git a/src/main/java/org/springframework/data/jpa/repository/support/Querydsl.java b/src/main/java/org/springframework/data/jpa/repository/support/Querydsl.java
index 5e33031ed..9ad51732b 100644
--- a/src/main/java/org/springframework/data/jpa/repository/support/Querydsl.java
+++ b/src/main/java/org/springframework/data/jpa/repository/support/Querydsl.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2014 the original author or authors.
+ * Copyright 2012-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -46,6 +46,7 @@ import com.querydsl.jpa.impl.JPAQuery;
  * 
  * @author Oliver Gierke
  * @author Thomas Darimont
+ * @author Mark Paluch
  */
 public class Querydsl {
 
@@ -61,8 +62,8 @@ public class Querydsl {
 	 */
 	public Querydsl(EntityManager em, PathBuilder<?> builder) {
 
-		Assert.notNull(em);
-		Assert.notNull(builder);
+		Assert.notNull(em, "EntityManager must not be null!");
+		Assert.notNull(builder, "PathBuilder must not be null!");
 
 		this.em = em;
 		this.provider = PersistenceProvider.fromEntityManager(em);
diff --git a/src/main/java/org/springframework/data/jpa/repository/support/SimpleJpaRepository.java b/src/main/java/org/springframework/data/jpa/repository/support/SimpleJpaRepository.java
index a64d34243..104f919d3 100644
--- a/src/main/java/org/springframework/data/jpa/repository/support/SimpleJpaRepository.java
+++ b/src/main/java/org/springframework/data/jpa/repository/support/SimpleJpaRepository.java
@@ -90,8 +90,8 @@ public class SimpleJpaRepository<T, ID extends Serializable>
 	 */
 	public SimpleJpaRepository(JpaEntityInformation<T, ?> entityInformation, EntityManager entityManager) {
 
-		Assert.notNull(entityInformation);
-		Assert.notNull(entityManager);
+		Assert.notNull(entityInformation, "JpaEntityInformation must not be null!");
+		Assert.notNull(entityManager, "EntityManager must not be null!");
 
 		this.entityInformation = entityInformation;
 		this.em = entityManager;
@@ -696,8 +696,9 @@ public class SimpleJpaRepository<T, ID extends Serializable>
 	private <S, U extends T> Root<U> applySpecificationToCriteria(Specification<U> spec, Class<U> domainClass,
 			CriteriaQuery<S> query) {
 
-		Assert.notNull(query);
-		Assert.notNull(domainClass);
+		Assert.notNull(domainClass, "Domain class must not be null!");
+		Assert.notNull(query, "CriteriaQuery must not be null!");
+
 		Root<U> root = query.from(domainClass);
 
 		if (spec == null) {
@@ -743,7 +744,7 @@ public class SimpleJpaRepository<T, ID extends Serializable>
 	 */
 	private static Long executeCountQuery(TypedQuery<Long> query) {
 
-		Assert.notNull(query);
+		Assert.notNull(query, "TypedQuery must not be null!");
 
 		List<Long> totals = query.getResultList();
 		Long total = 0L;
diff --git a/src/test/java/org/springframework/data/jpa/domain/sample/AuditorAwareStub.java b/src/test/java/org/springframework/data/jpa/domain/sample/AuditorAwareStub.java
index 34c39eabe..bbfc3314a 100644
--- a/src/test/java/org/springframework/data/jpa/domain/sample/AuditorAwareStub.java
+++ b/src/test/java/org/springframework/data/jpa/domain/sample/AuditorAwareStub.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2008-2011 the original author or authors.
+ * Copyright 2008-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -23,6 +23,7 @@ import org.springframework.util.Assert;
  * Stub implementation for {@link AuditorAware}. Returns {@literal null} for the current auditor.
  * 
  * @author Oliver Gierke
+ * @author Mark Paluch
  */
 public class AuditorAwareStub implements AuditorAware<AuditableUser> {
 
@@ -32,7 +33,7 @@ public class AuditorAwareStub implements AuditorAware<AuditableUser> {
 
 	public AuditorAwareStub(AuditableUserRepository repository) {
 
-		Assert.notNull(repository);
+		Assert.notNull(repository, "AuditableUserRepository must not be null!");
 		this.repository = repository;
 	}
 
diff --git a/src/test/java/org/springframework/data/jpa/domain/sample/SampleEntityPK.java b/src/test/java/org/springframework/data/jpa/domain/sample/SampleEntityPK.java
index 85c69a443..37769621c 100644
--- a/src/test/java/org/springframework/data/jpa/domain/sample/SampleEntityPK.java
+++ b/src/test/java/org/springframework/data/jpa/domain/sample/SampleEntityPK.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2008-2011 the original author or authors.
+ * Copyright 2008-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -40,8 +40,8 @@ public class SampleEntityPK implements Serializable {
 
 	public SampleEntityPK(String first, String second) {
 
-		Assert.notNull(first);
-		Assert.notNull(second);
+		Assert.notNull(first, "First must not be null!");
+		Assert.notNull(second, "Second must not be null!");
 		this.first = first;
 		this.second = second;
 	}
diff --git a/src/test/java/org/springframework/data/jpa/repository/config/CustomRepositoryFactoryConfigTests.java b/src/test/java/org/springframework/data/jpa/repository/config/CustomRepositoryFactoryConfigTests.java
index 876b8bfe6..953cb7ff8 100644
--- a/src/test/java/org/springframework/data/jpa/repository/config/CustomRepositoryFactoryConfigTests.java
+++ b/src/test/java/org/springframework/data/jpa/repository/config/CustomRepositoryFactoryConfigTests.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2008-2011 the original author or authors.
+ * Copyright 2008-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -38,6 +38,7 @@ import org.springframework.util.Assert;
  * intermediate interface.
  * 
  * @author Oliver Gierke
+ * @author Mark Paluch
  */
 @RunWith(SpringJUnit4ClassRunner.class)
 @ContextConfiguration(locations = "classpath:config/namespace-customfactory-context.xml")
@@ -57,8 +58,6 @@ public class CustomRepositoryFactoryConfigTests {
 
 	@Test(expected = UnsupportedOperationException.class)
 	public void testCustomFactoryUsed() {
-
-		Assert.notNull(userRepository);
 		userRepository.customMethod(1);
 	}