Add comprehensive tests for ModifiableLong modifications

src/main/java/de/rub/nds/modifiablevariable/biginteger/BigIntegerAddModification.java

@@ -38,7 +38,10 @@ public BigIntegerAddModification createCopy() {
 
     @Override
     protected BigInteger modifyImplementationHook(BigInteger input) {
-        return input == null ? summand : input.add(summand);
+        if (input == null) {
+            return null;
+        }
+        return input.add(summand);
     }
 
     public BigInteger getSummand() {

src/main/java/de/rub/nds/modifiablevariable/biginteger/BigIntegerExplicitValueModification.java

@@ -39,7 +39,7 @@ public BigIntegerExplicitValueModification createCopy() {
     @Override
     protected BigInteger modifyImplementationHook(BigInteger input) {
         if (input == null) {
-            throw new NullPointerException("original value must not be null");
+            return null;
         }
         return explicitValue;
     }

src/main/java/de/rub/nds/modifiablevariable/biginteger/BigIntegerMultiplyModification.java

@@ -38,7 +38,10 @@ public BigIntegerMultiplyModification createCopy() {
 
     @Override
     protected BigInteger modifyImplementationHook(BigInteger input) {
-        return input == null ? BigInteger.ZERO : input.multiply(factor);
+        if (input == null) {
+            return null;
+        }
+        return input.multiply(factor);
     }
 
     public BigInteger getFactor() {

src/main/java/de/rub/nds/modifiablevariable/biginteger/BigIntegerShiftLeftModification.java

@@ -38,7 +38,7 @@ public BigIntegerShiftLeftModification createCopy() {
     @Override
     protected BigInteger modifyImplementationHook(BigInteger input) {
         if (input == null) {
-            input = BigInteger.ZERO;
+            return null;
         }
         return input.shiftLeft(shift);
     }

src/main/java/de/rub/nds/modifiablevariable/biginteger/BigIntegerShiftRightModification.java

@@ -38,7 +38,7 @@ public BigIntegerShiftRightModification createCopy() {
     @Override
     protected BigInteger modifyImplementationHook(BigInteger input) {
         if (input == null) {
-            input = BigInteger.ZERO;
+            return null;
         }
         return input.shiftRight(shift);
     }

src/main/java/de/rub/nds/modifiablevariable/biginteger/BigIntegerSubtractModification.java

@@ -39,7 +39,7 @@ public BigIntegerSubtractModification createCopy() {
     @Override
     protected BigInteger modifyImplementationHook(BigInteger input) {
         if (input == null) {
-            input = BigInteger.ZERO;
+            return null;
         }
         return input.subtract(subtrahend);
     }

src/main/java/de/rub/nds/modifiablevariable/biginteger/BigIntegerXorModification.java

@@ -39,7 +39,7 @@ public BigIntegerXorModification createCopy() {
     @Override
     protected BigInteger modifyImplementationHook(BigInteger input) {
         if (input == null) {
-            input = BigInteger.ZERO;
+            return null;
         }
         return input.xor(xor);
     }

src/main/java/de/rub/nds/modifiablevariable/bool/BooleanExplicitValueModification.java

@@ -37,7 +37,7 @@ public BooleanExplicitValueModification createCopy() {
     @Override
     protected Boolean modifyImplementationHook(Boolean input) {
         if (input == null) {
-            throw new NullPointerException("original value must not be null");
+            return null;
         }
         return explicitValue;
     }

src/main/java/de/rub/nds/modifiablevariable/bool/BooleanToggleModification.java

@@ -28,6 +28,9 @@ public BooleanToggleModification createCopy() {
 
     @Override
     protected Boolean modifyImplementationHook(Boolean input) {
+        if (input == null) {
+            return null;
+        }
         return !input;
     }
 

src/main/java/de/rub/nds/modifiablevariable/bytearray/ByteArrayAppendValueModification.java

@@ -41,6 +41,9 @@ public ByteArrayAppendValueModification createCopy() {
 
     @Override
     protected byte[] modifyImplementationHook(byte[] input) {
+        if (input == null) {
+            return null;
+        }
         return ArrayConverter.concatenate(input, bytesToAppend);
     }
 

src/main/java/de/rub/nds/modifiablevariable/bytearray/ByteArrayDeleteModification.java

@@ -42,6 +42,9 @@ public ByteArrayDeleteModification createCopy() {
 
     @Override
     protected byte[] modifyImplementationHook(byte[] input) {
+        if (input == null) {
+            return null;
+        }
         if (input.length == 0) {
             return input;
         }

src/main/java/de/rub/nds/modifiablevariable/bytearray/ByteArrayDuplicateModification.java

@@ -30,7 +30,7 @@ public ByteArrayDuplicateModification createCopy() {
     @Override
     protected byte[] modifyImplementationHook(byte[] input) {
         if (input == null) {
-            input = new byte[0];
+            return null;
         }
         return ArrayConverter.concatenate(input, input);
     }

src/main/java/de/rub/nds/modifiablevariable/bytearray/ByteArrayExplicitValueModification.java

@@ -42,7 +42,7 @@ public ByteArrayExplicitValueModification createCopy() {
     @Override
     protected byte[] modifyImplementationHook(byte[] input) {
         if (input == null) {
-            throw new NullPointerException("original value must not be null");
+            return null;
         }
         return explicitValue.clone();
     }

src/main/java/de/rub/nds/modifiablevariable/bytearray/ByteArrayInsertValueModification.java

@@ -46,9 +46,8 @@ public ByteArrayInsertValueModification createCopy() {
     @Override
     protected byte[] modifyImplementationHook(byte[] input) {
         if (input == null) {
-            input = new byte[0];
+            return null;
         }
-
         // Wrap around and also allow to insert at the end of the original value
         int insertPosition = startPosition % (input.length + 1);
         if (startPosition < 0) {

src/main/java/de/rub/nds/modifiablevariable/bytearray/ByteArrayPrependValueModification.java

@@ -42,9 +42,8 @@ public ByteArrayPrependValueModification createCopy() {
     @Override
     protected byte[] modifyImplementationHook(byte[] input) {
         if (input == null) {
-            input = new byte[0];
+            return null;
         }
-
         return ArrayConverter.concatenate(bytesToPrepend, input);
     }
 

src/main/java/de/rub/nds/modifiablevariable/bytearray/ByteArrayXorModification.java

@@ -46,7 +46,7 @@ public ByteArrayXorModification createCopy() {
     @Override
     protected byte[] modifyImplementationHook(byte[] input) {
         if (input == null) {
-            input = new byte[0];
+            return null;
         }
         if (input.length == 0) {
             return input;

src/main/java/de/rub/nds/modifiablevariable/integer/IntegerAddModification.java

@@ -37,6 +37,9 @@ public IntegerAddModification createCopy() {
 
     @Override
     protected Integer modifyImplementationHook(Integer input) {
+        if (input == null) {
+            return null;
+        }
         return input + summand;
     }
 

src/main/java/de/rub/nds/modifiablevariable/integer/IntegerExplicitValueModification.java

@@ -38,7 +38,7 @@ public IntegerExplicitValueModification createCopy() {
     @Override
     protected Integer modifyImplementationHook(Integer input) {
         if (input == null) {
-            throw new NullPointerException("original value must not be null");
+            return null;
         }
         return explicitValue;
     }

src/main/java/de/rub/nds/modifiablevariable/integer/IntegerMultiplyModification.java

@@ -37,6 +37,9 @@ public IntegerMultiplyModification createCopy() {
 
     @Override
     protected Integer modifyImplementationHook(Integer input) {
+        if (input == null) {
+            return null;
+        }
         return input * factor;
     }
 

src/main/java/de/rub/nds/modifiablevariable/integer/IntegerShiftLeftModification.java

@@ -38,6 +38,9 @@ public IntegerShiftLeftModification createCopy() {
 
     @Override
     protected Integer modifyImplementationHook(Integer input) {
+        if (input == null) {
+            return null;
+        }
         return input << shift % MAX_SHIFT_MODIFIER;
     }
 

src/main/java/de/rub/nds/modifiablevariable/integer/IntegerShiftRightModification.java

@@ -38,6 +38,9 @@ public IntegerShiftRightModification createCopy() {
 
     @Override
     protected Integer modifyImplementationHook(Integer input) {
+        if (input == null) {
+            return null;
+        }
         return input >> shift % MAX_SHIFT_MODIFIER;
     }
 

src/main/java/de/rub/nds/modifiablevariable/integer/IntegerSubtractModification.java

@@ -37,6 +37,9 @@ public IntegerSubtractModification createCopy() {
 
     @Override
     protected Integer modifyImplementationHook(Integer input) {
+        if (input == null) {
+            return null;
+        }
         return input - subtrahend;
     }
 

src/main/java/de/rub/nds/modifiablevariable/integer/IntegerSwapEndianModification.java

@@ -28,6 +28,9 @@ public IntegerSwapEndianModification createCopy() {
 
     @Override
     protected Integer modifyImplementationHook(Integer input) {
+        if (input == null) {
+            return null;
+        }
         return Integer.reverseBytes(input);
     }
 

src/main/java/de/rub/nds/modifiablevariable/integer/IntegerXorModification.java

@@ -37,6 +37,9 @@ public IntegerXorModification createCopy() {
 
     @Override
     protected Integer modifyImplementationHook(Integer input) {
+        if (input == null) {
+            return null;
+        }
         return input ^ xor;
     }
 

src/main/java/de/rub/nds/modifiablevariable/longint/LongAddModification.java

@@ -37,6 +37,9 @@ public LongAddModification createCopy() {
 
     @Override
     protected Long modifyImplementationHook(Long input) {
+        if (input == null) {
+            return null;
+        }
         return input + summand;
     }
 

src/main/java/de/rub/nds/modifiablevariable/longint/LongExplicitValueModification.java

@@ -38,7 +38,7 @@ public LongExplicitValueModification createCopy() {
     @Override
     protected Long modifyImplementationHook(Long input) {
         if (input == null) {
-            throw new NullPointerException("original value must not be null");
+            return null;
         }
         return explicitValue;
     }

src/main/java/de/rub/nds/modifiablevariable/longint/LongMultiplyModification.java

@@ -37,7 +37,10 @@ public LongMultiplyModification createCopy() {
 
     @Override
     protected Long modifyImplementationHook(Long input) {
-        return input == null ? 0L : input * factor;
+        if (input == null) {
+            return null;
+        }
+        return input * factor;
     }
 
     public Long getFactor() {

src/main/java/de/rub/nds/modifiablevariable/longint/LongShiftLeftModification.java

@@ -39,7 +39,10 @@ public LongShiftLeftModification createCopy() {
 
     @Override
     protected Long modifyImplementationHook(Long input) {
-        return input == null ? 0L : input << shift % MAX_SHIFT_MODIFIER;
+        if (input == null) {
+            return null;
+        }
+        return input << shift % MAX_SHIFT_MODIFIER;
     }
 
     public int getShift() {

src/main/java/de/rub/nds/modifiablevariable/longint/LongShiftRightModification.java

@@ -39,7 +39,10 @@ public LongShiftRightModification createCopy() {
 
     @Override
     protected Long modifyImplementationHook(Long input) {
-        return input == null ? 0L : input >> shift % MAX_SHIFT_MODIFIER;
+        if (input == null) {
+            return null;
+        }
+        return input >> shift % MAX_SHIFT_MODIFIER;
     }
 
     public int getShift() {

src/main/java/de/rub/nds/modifiablevariable/longint/LongSubtractModification.java

@@ -37,7 +37,10 @@ public LongSubtractModification createCopy() {
 
     @Override
     protected Long modifyImplementationHook(Long input) {
-        return input == null ? -subtrahend : input - subtrahend;
+        if (input == null) {
+            return null;
+        }
+        return input - subtrahend;
     }
 
     public Long getSubtrahend() {

src/main/java/de/rub/nds/modifiablevariable/longint/LongXorModification.java

@@ -37,7 +37,10 @@ public LongXorModification createCopy() {
 
     @Override
     protected Long modifyImplementationHook(Long input) {
-        return input == null ? xor : input ^ xor;
+        if (input == null) {
+            return null;
+        }
+        return input ^ xor;
     }
 
     public Long getXor() {

src/main/java/de/rub/nds/modifiablevariable/singlebyte/ByteAddModification.java

@@ -38,7 +38,7 @@ public ByteAddModification createCopy() {
     @Override
     protected Byte modifyImplementationHook(Byte input) {
         if (input == null) {
-            input = 0;
+            return null;
         }
         return (byte) (input + summand);
     }

src/main/java/de/rub/nds/modifiablevariable/singlebyte/ByteExplicitValueModification.java

@@ -38,7 +38,7 @@ public ByteExplicitValueModification createCopy() {
     @Override
     protected Byte modifyImplementationHook(Byte input) {
         if (input == null) {
-            throw new NullPointerException("original value must not be null");
+            return null;
         }
         return explicitValue;
     }

src/main/java/de/rub/nds/modifiablevariable/singlebyte/ByteSubtractModification.java

@@ -38,7 +38,7 @@ public ByteSubtractModification createCopy() {
     @Override
     protected Byte modifyImplementationHook(Byte input) {
         if (input == null) {
-            input = 0;
+            return null;
         }
         return (byte) (input - subtrahend);
     }

src/main/java/de/rub/nds/modifiablevariable/singlebyte/ByteXorModification.java

@@ -38,7 +38,7 @@ public ByteXorModification createCopy() {
     @Override
     protected Byte modifyImplementationHook(Byte input) {
         if (input == null) {
-            input = 0;
+            return null;
         }
         return (byte) (input ^ xor);
     }

src/main/java/de/rub/nds/modifiablevariable/string/StringAppendValueModification.java

@@ -43,7 +43,10 @@ public StringAppendValueModification createCopy() {
 
     @Override
     protected String modifyImplementationHook(String input) {
-        return input != null ? input + appendValue : appendValue;
+        if (input == null) {
+            return null;
+        }
+        return input + appendValue;
     }
 
     public String getAppendValue() {

src/main/java/de/rub/nds/modifiablevariable/string/StringExplicitValueModification.java

@@ -43,7 +43,7 @@ public StringExplicitValueModification createCopy() {
     @Override
     protected String modifyImplementationHook(String input) {
         if (input == null) {
-            throw new NullPointerException("original value must not be null");
+            return null;
         }
         return explicitValue;
     }

src/main/java/de/rub/nds/modifiablevariable/string/StringPrependValueModification.java

@@ -43,7 +43,10 @@ public StringPrependValueModification createCopy() {
 
     @Override
     protected String modifyImplementationHook(String input) {
-        return input != null ? prependValue + input : prependValue;
+        if (input == null) {
+            return null;
+        }
+        return prependValue + input;
     }
 
     public String getPrependValue() {