--- /dev/null
+#ifndef OPENTRACING_MOCKTRACER_JSON_H
+#define OPENTRACING_MOCKTRACER_JSON_H
+
+#include <opentracing/mocktracer/recorder.h>
+#include <opentracing/mocktracer/symbols.h>
+#include <vector>
+
+namespace opentracing {
+BEGIN_OPENTRACING_ABI_NAMESPACE
+namespace mocktracer {
+// Serialize provided spans to JSON.
+OPENTRACING_MOCK_TRACER_API void ToJson(std::ostream& writer,
+ const std::vector<SpanData>& spans);
+} // namespace mocktracer
+END_OPENTRACING_ABI_NAMESPACE
+} // namespace opentracing
+
+#endif // OPENTRACING_MOCKTRACER_JSON_H