Test that DynamicJsonBuffer can't alloc more than BLOCK_CAPACITY

include/ArduinoJson/DynamicJsonBuffer.hpp

@@ -19,14 +19,21 @@ class DynamicJsonBuffer : public JsonBuffer {
 
   size_t size() const { return _size; }
 
+  static const size_t BLOCK_CAPACITY = 32;
+
  protected:
   virtual void* alloc(size_t bytes) {
+    if (bytes > BLOCK_CAPACITY) return NULL;
     void* p = _buffer + _size;
     _size += bytes;
     return p;
   }
 
-  static const size_t BLOCK_CAPACITY = 32;
+  bool canStore(size_t bytes) {
+    // by design a DynamicJsonBuffer can't alloc a block bigger than
+    // BLOCK_CAPACITY
+    return bytes < BLOCK_CAPACITY;
+  }
 
   size_t _size;
   uint8_t _buffer[BLOCK_CAPACITY];

test/DynamicJsonBuffer_Basic_Tests.cpp

@@ -21,14 +21,24 @@ TEST_F(DynamicJsonBuffer_Basic_Tests, InitialSizeIsZero) {
 }
 
 TEST_F(DynamicJsonBuffer_Basic_Tests, GrowsAfterAlloc) {
-  buffer.alloc(100);
-  ASSERT_EQ(100, buffer.size());
-  buffer.alloc(100);
-  ASSERT_EQ(200, buffer.size());
+  buffer.alloc(1);
+  ASSERT_EQ(1, buffer.size());
+  buffer.alloc(1);
+  ASSERT_EQ(2, buffer.size());
+}
+
+TEST_F(DynamicJsonBuffer_Basic_Tests, CanAllocLessThanBlockCapacity) {
+  void* p = buffer.alloc(DynamicJsonBuffer::BLOCK_CAPACITY);
+  ASSERT_TRUE(p);
+}
+
+TEST_F(DynamicJsonBuffer_Basic_Tests, CantAllocMoreThanBlockCapacity) {
+  void* p = buffer.alloc(DynamicJsonBuffer::BLOCK_CAPACITY + 1);
+  ASSERT_FALSE(p);
 }
 
 TEST_F(DynamicJsonBuffer_Basic_Tests, ReturnDifferentPointer) {
-  void* p1 = buffer.alloc(100);
-  void* p2 = buffer.alloc(200);
+  void* p1 = buffer.alloc(1);
+  void* p2 = buffer.alloc(2);
   ASSERT_NE(p1, p2);
 }