diff --git a/src/storage/dd/CuddDd.cpp b/src/storage/dd/CuddDd.cpp
index eba51a557..aa3b7c675 100644
--- a/src/storage/dd/CuddDd.cpp
+++ b/src/storage/dd/CuddDd.cpp
@@ -326,12 +326,16 @@ namespace storm {
         }
         
         void Dd<CUDD>::exportToDot(std::string const& filename) const {
-            FILE* filePointer = fopen(filename.c_str() , "w");
-            this->getDdManager()->getCuddManager().DumpDot({this->cuddAdd}, nullptr, nullptr, filePointer);
-            fclose(filePointer);
+            if (filename.empty()) {
+                this->getDdManager()->getCuddManager().DumpDot({this->getCuddAdd()});
+            } else {
+                FILE* filePointer = fopen(filename.c_str() , "w");
+                this->getDdManager()->getCuddManager().DumpDot({this->getCuddAdd()}, nullptr, nullptr, filePointer);
+                fclose(filePointer);
+            }
         }
         
-        ADD Dd<CUDD>::getCuddAdd() {
+        ADD& Dd<CUDD>::getCuddAdd() {
             return this->cuddAdd;
         }
         
@@ -350,5 +354,11 @@ namespace storm {
         std::shared_ptr<DdManager<CUDD>> Dd<CUDD>::getDdManager() const {
             return this->ddManager;
         }
+        
+        std::ostream & operator<<(std::ostream& out, const Dd<CUDD>& dd) {
+            dd.exportToDot();
+            return out;
+        }
+
     }
 }
\ No newline at end of file
diff --git a/src/storage/dd/CuddDd.h b/src/storage/dd/CuddDd.h
index 1f8339fe6..0255ae58e 100644
--- a/src/storage/dd/CuddDd.h
+++ b/src/storage/dd/CuddDd.h
@@ -4,6 +4,7 @@
 #include <unordered_map>
 #include <set>
 #include <memory>
+#include <iostream>
 
 #include "src/storage/dd/Dd.h"
 #include "src/utility/OsDetection.h"
@@ -345,7 +346,7 @@ namespace storm {
              *
              * @param filename The name of the file to which the DD is to be exported.
              */
-            void exportToDot(std::string const& filename) const;
+            void exportToDot(std::string const& filename = "") const;
             
             /*!
              * Retrieves the manager that is responsible for this DD.
@@ -354,13 +355,14 @@ namespace storm {
              */
             std::shared_ptr<DdManager<CUDD>> getDdManager() const;
             
+            friend std::ostream & operator<<(std::ostream& out, const Dd<CUDD>& dd);
         private:
             /*!
-             * Retrieves the CUDD ADD object associated with this DD.
+             * Retrieves a reference to the CUDD ADD object associated with this DD.
              *
-             * @return The CUDD ADD object assoicated with this DD.
+             * @return The CUDD ADD object associated with this DD.
              */
-            ADD getCuddAdd();
+            ADD& getCuddAdd();
             
             /*!
              * Retrieves the CUDD ADD object associated with this DD.
diff --git a/src/storage/dd/CuddDdManager.cpp b/src/storage/dd/CuddDdManager.cpp
index dd6ce4f4f..4b96e685a 100644
--- a/src/storage/dd/CuddDdManager.cpp
+++ b/src/storage/dd/CuddDdManager.cpp
@@ -4,8 +4,6 @@
 #include "src/storage/dd/CuddDdManager.h"
 #include "src/exceptions/InvalidArgumentException.h"
 
-#include <iostream>
-
 namespace storm {
     namespace dd {
         DdManager<CUDD>::DdManager() : metaVariableMap(), cuddManager() {
@@ -25,7 +23,17 @@ namespace storm {
         }
         
         Dd<CUDD> DdManager<CUDD>::getEncoding(std::string const& metaVariableName, int_fast64_t value) {
-            std::vector<Dd<CUDD>> ddVariables = this->getMetaVariable(metaVariableName).getDdVariables();
+            // Check whether the meta variable exists.
+            if (!this->hasMetaVariable(metaVariableName)) {
+                throw storm::exceptions::InvalidArgumentException() << "Unknown meta variable name '" << metaVariableName << "'.";
+            }
+            
+            // Check whether the value is legal for this meta variable.
+            if (value < this->getMetaVariable(metaVariableName).getLow() || value > this->getMetaVariable(metaVariableName).getHigh()) {
+                throw storm::exceptions::InvalidArgumentException() << "Illegal value " << value << " for meta variable '" << metaVariableName << "'.";
+            }
+            
+            std::vector<Dd<CUDD>> const& ddVariables = this->getMetaVariable(metaVariableName).getDdVariables();
 
             Dd<CUDD> result;
             if (value & (1ull << (ddVariables.size() - 1))) {
@@ -120,7 +128,7 @@ namespace storm {
             auto const& nameVariablePair = metaVariableMap.find(metaVariableName);
             
             if (!this->hasMetaVariable(metaVariableName)) {
-                throw storm::exceptions::InvalidArgumentException() << "Unknown meta variable name.";
+                throw storm::exceptions::InvalidArgumentException() << "Unknown meta variable name '" << metaVariableName << "'.";
             }
             
             return nameVariablePair->second;
diff --git a/test/functional/storage/CuddDdTest.cpp b/test/functional/storage/CuddDdTest.cpp
index a92dbc929..fb6856c75 100644
--- a/test/functional/storage/CuddDdTest.cpp
+++ b/test/functional/storage/CuddDdTest.cpp
@@ -36,7 +36,7 @@ TEST(CuddDdManager, Constants) {
     EXPECT_EQ(2, two.getMax());
 }
 
-TEST(CuddDdManager, MetaVariableTest) {
+TEST(CuddDdManager, AddMetaVariableTest) {
     std::shared_ptr<storm::dd::DdManager<storm::dd::CUDD>> manager(new storm::dd::DdManager<storm::dd::CUDD>());
     
     ASSERT_NO_THROW(manager->addMetaVariable("x", 1, 9));
@@ -60,6 +60,29 @@ TEST(CuddDdManager, MetaVariableTest) {
     
     ASSERT_THROW(storm::dd::DdMetaVariable<storm::dd::CUDD> const& metaVariableX = manager->getMetaVariable("x'"), storm::exceptions::InvalidArgumentException);
     ASSERT_NO_THROW(storm::dd::DdMetaVariable<storm::dd::CUDD> const& metaVariableX = manager->getMetaVariable("x"));
+}
+
+TEST(CuddDdManager, EncodingTest) {
+    std::shared_ptr<storm::dd::DdManager<storm::dd::CUDD>> manager(new storm::dd::DdManager<storm::dd::CUDD>());
+    
+    ASSERT_NO_THROW(manager->addMetaVariable("x", 1, 9));
+    
+    storm::dd::Dd<storm::dd::CUDD> encoding;
+    ASSERT_THROW(encoding = manager->getEncoding("x", 0), storm::exceptions::InvalidArgumentException);
+    ASSERT_THROW(encoding = manager->getEncoding("x", 10), storm::exceptions::InvalidArgumentException);
+    ASSERT_NO_THROW(encoding = manager->getEncoding("x", 4));
+    encoding.exportToDot("out.dot");
+    EXPECT_EQ(1, encoding.getNonZeroCount());
+    EXPECT_EQ(6, encoding.getNodeCount());
+    EXPECT_EQ(2, encoding.getLeafCount());
+}
+
+TEST(CuddDdMetaVariable, AccessorTest) {
+    std::shared_ptr<storm::dd::DdManager<storm::dd::CUDD>> manager(new storm::dd::DdManager<storm::dd::CUDD>());
+    
+    ASSERT_NO_THROW(manager->addMetaVariable("x", 1, 9));
+    EXPECT_EQ(1, manager->getNumberOfMetaVariables());
+    ASSERT_NO_THROW(storm::dd::DdMetaVariable<storm::dd::CUDD> const& metaVariableX = manager->getMetaVariable("x"));
     storm::dd::DdMetaVariable<storm::dd::CUDD> const& metaVariableX = manager->getMetaVariable("x");
     
     EXPECT_EQ(1, metaVariableX.getLow());
@@ -69,3 +92,13 @@ TEST(CuddDdManager, MetaVariableTest) {
     EXPECT_EQ(4, metaVariableX.getNumberOfDdVariables());
 }
 
+//TEST(CuddDd, OperatorTest) {
+//    std::shared_ptr<storm::dd::DdManager<storm::dd::CUDD>> manager(new storm::dd::DdManager<storm::dd::CUDD>());
+//    
+//    ASSERT_NO_THROW(manager->addMetaVariable("x", 1, 9));
+//    EXPECT_EQ(manager->getZero(), manager->getZero());
+//    EXPECT_NE(manager->getZero(), manager->getOne());
+//    
+//    storm::dd::Dd<storm::dd::CUDD> add;
+//    
+//}