diff --git a/extras/tests/Helpers/Allocators.hpp b/extras/tests/Helpers/Allocators.hpp
index 8bae2cd6..06984b82 100644
--- a/extras/tests/Helpers/Allocators.hpp
+++ b/extras/tests/Helpers/Allocators.hpp
@@ -6,6 +6,8 @@
 
 #include <ArduinoJson/Memory/Allocator.hpp>
 
+#include <sstream>
+
 struct FailingAllocator : ArduinoJson::Allocator {
   static FailingAllocator* instance() {
     static FailingAllocator allocator;
@@ -26,3 +28,30 @@ struct FailingAllocator : ArduinoJson::Allocator {
     return nullptr;
   }
 };
+
+class SpyingAllocator : public ArduinoJson::Allocator {
+ public:
+  virtual ~SpyingAllocator() {}
+
+  void* allocate(size_t n) override {
+    _log << "A" << n;
+    return malloc(n);
+  }
+
+  void deallocate(void* p) override {
+    _log << "F";
+    free(p);
+  }
+
+  void* reallocate(void* ptr, size_t n) override {
+    _log << "R" << n;
+    return realloc(ptr, n);
+  }
+
+  std::string log() const {
+    return _log.str();
+  }
+
+ private:
+  std::ostringstream _log;
+};
diff --git a/extras/tests/JsonDocument/allocator.cpp b/extras/tests/JsonDocument/allocator.cpp
index 3a85f1a8..920d1475 100644
--- a/extras/tests/JsonDocument/allocator.cpp
+++ b/extras/tests/JsonDocument/allocator.cpp
@@ -5,38 +5,12 @@
 #include <ArduinoJson.h>
 #include <stdlib.h>  // malloc, free
 #include <catch.hpp>
-#include <sstream>
 #include <utility>
 
+#include "Allocators.hpp"
+
 using ArduinoJson::detail::sizeofObject;
 
-class SpyingAllocator : public Allocator {
- public:
-  virtual ~SpyingAllocator() {}
-
-  void* allocate(size_t n) override {
-    _log << "A" << n;
-    return malloc(n);
-  }
-
-  void deallocate(void* p) override {
-    _log << "F";
-    free(p);
-  }
-
-  void* reallocate(void* ptr, size_t n) override {
-    _log << "R" << n;
-    return realloc(ptr, n);
-  }
-
-  std::string log() const {
-    return _log.str();
-  }
-
- private:
-  std::ostringstream _log;
-};
-
 class ControllableAllocator : public Allocator {
  public:
   ControllableAllocator() : _enabled(true) {}