diff --git a/backend/Makefile.am b/backend/Makefile.am
index 70aa5d0f6..c2498ae67 100644
--- a/backend/Makefile.am
+++ b/backend/Makefile.am
@@ -487,12 +487,12 @@ libgenesys_la_SOURCES = genesys.cc genesys.h genesys_sanei.h genesys_sanei.cc ge
     genesys_gl847.cc genesys_gl847.h genesys_gl124.cc genesys_gl124.h \
     genesys_low.cc genesys_low.h
 
-libgenesys_la_CPPFLAGS = $(AM_CPPFLAGS) -DBACKEND_NAME=genesys
+libgenesys_la_CPPFLAGS = $(AM_CPPFLAGS) -DBACKEND_NAME=genesys $(XML_CFLAGS)
 
 nodist_libsane_genesys_la_SOURCES = genesys-s.cc
 libsane_genesys_la_CPPFLAGS = $(AM_CPPFLAGS) -DBACKEND_NAME=genesys
 libsane_genesys_la_LDFLAGS = $(DIST_SANELIBS_LDFLAGS)
-libsane_genesys_la_LIBADD = $(COMMON_LIBS) libgenesys.la  ../sanei/sanei_magic.lo ../sanei/sanei_init_debug.lo ../sanei/sanei_constrain_value.lo ../sanei/sanei_config.lo sane_strstatus.lo ../sanei/sanei_usb.lo $(MATH_LIB) $(USB_LIBS) $(RESMGR_LIBS)
+libsane_genesys_la_LIBADD = $(COMMON_LIBS) libgenesys.la  ../sanei/sanei_magic.lo ../sanei/sanei_init_debug.lo ../sanei/sanei_constrain_value.lo ../sanei/sanei_config.lo sane_strstatus.lo ../sanei/sanei_usb.lo $(MATH_LIB) $(USB_LIBS) $(XML_LIBS) $(RESMGR_LIBS)
 EXTRA_DIST += genesys.conf.in
 # TODO: Why are this distributed but not compiled?
 EXTRA_DIST += genesys_conv.cc genesys_conv_hlp.cc genesys_devices.cc
diff --git a/backend/genesys_sanei.cc b/backend/genesys_sanei.cc
index 5b5b40aa9..33d645e6f 100644
--- a/backend/genesys_sanei.cc
+++ b/backend/genesys_sanei.cc
@@ -45,6 +45,10 @@
 
 #include "genesys_sanei.h"
 
+#if WITH_USB_RECORD_REPLAY
+#include <libxml/tree.h>
+#endif
+
 UsbDevice::~UsbDevice()
 {
     if (is_open()) {
@@ -138,3 +142,131 @@ void UsbDevice::set_not_open()
     is_open_ = false;
     name_ = "";
 }
+
+extern "C" {
+    typedef enum {
+        sanei_usb_testing_mode_disabled = 0,
+        sanei_usb_testing_mode_record,
+        sanei_usb_testing_mode_replay,
+    }
+    sanei_usb_testing_mode;
+
+    extern sanei_usb_testing_mode testing_mode;
+} // extern "C"
+
+#if WITH_USB_RECORD_REPLAY
+
+// from sanei_usb.c
+#define FAIL_TEST(func, ...)                                                   \
+  do {                                                                         \
+    DBG(1, "%s: FAIL: ", func);                                                \
+    DBG(1, __VA_ARGS__);                                                       \
+    fail_test();                                                               \
+  } while (0)
+
+#define FAIL_TEST_TX(func, node, ...)                                          \
+  do {                                                                         \
+    sanei_xml_print_seq_if_any(node, func);                                    \
+    DBG(1, "%s: FAIL: ", func);                                                \
+    DBG(1, __VA_ARGS__);                                                       \
+    fail_test();                                                               \
+  } while (0)
+
+extern "C" {
+    void fail_test();
+    xmlNode* sanei_xml_get_next_tx_node();
+    int sanei_xml_is_known_commands_end(xmlNode* node);
+    void sanei_xml_print_seq_if_any(xmlNode* node, const char* parent_fun);
+    void sanei_xml_set_uint_attr(xmlNode* node, const char* attr_name,
+                                 unsigned attr_value);
+    xmlNode* sanei_xml_append_command(xmlNode* sibling,
+                                      int indent, xmlNode* e_command);
+    void sanei_xml_record_seq(xmlNode* node);
+    void sanei_xml_break_if_needed(xmlNode* node);
+    int sanei_usb_check_attr(xmlNode* node, const char* attr_name,
+                             const char* expected, const char* parent_fun);
+
+    extern xmlNode* testing_append_commands_node;
+    extern unsigned testing_last_known_seq;
+    extern int testing_development_mode;
+    extern int testing_known_commands_input_failed;
+} // extern "C"
+
+static void sanei_usb_record_debug_msg(xmlNode* node, SANE_String_Const message)
+{
+  int node_was_null = node == NULL;
+  if (node_was_null)
+    node = testing_append_commands_node;
+
+  xmlNode* e_tx = xmlNewNode(NULL, (const xmlChar*)"debug");
+  sanei_xml_set_uint_attr(e_tx, "seq", ++testing_last_known_seq);
+  xmlNewProp(e_tx, (const xmlChar*)"message", (const xmlChar*)message);
+
+  node = sanei_xml_append_command(node, node_was_null, e_tx);
+
+  if (node_was_null)
+    testing_append_commands_node = node;
+}
+
+static void sanei_usb_record_replace_debug_msg(xmlNode* node, SANE_String_Const message)
+{
+  if (!testing_development_mode)
+    return;
+
+  testing_last_known_seq--;
+  sanei_usb_record_debug_msg(node, message);
+  xmlUnlinkNode(node);
+  xmlFreeNode(node);
+}
+
+static void sanei_usb_replay_debug_msg(SANE_String_Const message)
+{
+  if (testing_known_commands_input_failed)
+    return;
+
+  xmlNode* node = sanei_xml_get_next_tx_node();
+  if (node == NULL)
+    {
+      FAIL_TEST(__func__, "no more transactions\n");
+      return;
+    }
+
+  if (sanei_xml_is_known_commands_end(node))
+    {
+      sanei_usb_record_debug_msg(NULL, message);
+      return;
+    }
+
+  sanei_xml_record_seq(node);
+  sanei_xml_break_if_needed(node);
+
+  if (xmlStrcmp(node->name, (const xmlChar*)"debug") != 0)
+    {
+      FAIL_TEST_TX(__func__, node, "unexpected transaction type %s\n",
+                   (const char*) node->name);
+      sanei_usb_record_replace_debug_msg(node, message);
+    }
+
+  if (!sanei_usb_check_attr(node, "message", message, __func__))
+    {
+      sanei_usb_record_replace_debug_msg(node, message);
+    }
+}
+
+void sanei_usb_testing_record_message(SANE_String_Const message)
+{
+  if (testing_mode == sanei_usb_testing_mode_record)
+    {
+      sanei_usb_record_debug_msg(NULL, message);
+    }
+  if (testing_mode == sanei_usb_testing_mode_replay)
+    {
+      sanei_usb_replay_debug_msg(message);
+    }
+}
+#else
+void sanei_usb_testing_record_message(SANE_String_Const message)
+{
+    (void) message;
+}
+#endif
diff --git a/backend/genesys_sanei.h b/backend/genesys_sanei.h
index 0e4160047..7aafdb0fc 100644
--- a/backend/genesys_sanei.h
+++ b/backend/genesys_sanei.h
@@ -94,4 +94,6 @@ private:
     int device_num_ = 0;
 };
 
+void sanei_usb_testing_record_message(SANE_String_Const message);
+
 #endif // BACKEND_GENESYS_SANEI_H
diff --git a/include/sane/sanei_usb.h b/include/sane/sanei_usb.h
index 8492d377e..1c1699d88 100644
--- a/include/sane/sanei_usb.h
+++ b/include/sane/sanei_usb.h
@@ -224,6 +224,13 @@ extern SANE_String sanei_usb_testing_get_backend();
  */
 extern SANE_Bool sanei_usb_is_replay_mode_enabled();
 
+/** Records a debug message in the captured USB data if testing mode is enabled. If testing mode
+ * is not enabled, this function does nothing.
+ *
+ * @param msg Message to record
+ */
+extern void sanei_usb_testing_record_message(SANE_String_Const message);
+
 /** Initialize sanei_usb.
  *
  * Call this before any other sanei_usb function.
diff --git a/sanei/sanei_usb.c b/sanei/sanei_usb.c
index af672e5ec..2c853482c 100644
--- a/sanei/sanei_usb.c
+++ b/sanei/sanei_usb.c
@@ -191,10 +191,10 @@ typedef enum
 sanei_usb_testing_mode;
 
 // Whether testing mode has been enabled
-static sanei_usb_testing_mode testing_mode = sanei_usb_testing_mode_disabled;
+sanei_usb_testing_mode testing_mode = sanei_usb_testing_mode_disabled;
 
 #if WITH_USB_RECORD_REPLAY
-static int testing_development_mode = 0;
+int testing_development_mode = 0;
 int testing_known_commands_input_failed = 0;
 unsigned testing_last_known_seq = 0;
 SANE_String testing_record_backend = NULL;
@@ -577,7 +577,7 @@ static int sanei_xml_get_prop_uint(xmlNode* node, const char* name)
   return attr_uint;
 }
 
-static void sanei_xml_print_seq_if_any(xmlNode* node, const char* parent_fun)
+void sanei_xml_print_seq_if_any(xmlNode* node, const char* parent_fun)
 {
   char* attr = sanei_xml_get_prop(node, "seq");
   if (attr == NULL)
@@ -627,7 +627,7 @@ static int sanei_xml_is_transaction_ignored(xmlNode* node)
 static xmlNode* sanei_xml_skip_non_tx_nodes(xmlNode* node)
 {
   const char* known_node_names[] = {
-    "control_tx", "bulk_tx", "interrupt_tx", "known_commands_end"
+    "control_tx", "bulk_tx", "interrupt_tx", "debug", "known_commands_end"
   };
 
   while (node != NULL)
@@ -653,7 +653,7 @@ static xmlNode* sanei_xml_skip_non_tx_nodes(xmlNode* node)
   return node;
 }
 
-static int sanei_xml_is_known_commands_end(xmlNode* node)
+int sanei_xml_is_known_commands_end(xmlNode* node)
 {
   if (!testing_development_mode || node == NULL)
     return 0;
@@ -667,7 +667,7 @@ static xmlNode* sanei_xml_peek_next_tx_node()
 }
 
 // returns next transaction node that is not get_descriptor
-static xmlNode* sanei_xml_get_next_tx_node()
+xmlNode* sanei_xml_get_next_tx_node()
 {
   xmlNode* next = testing_xml_next_tx_node;
 
@@ -802,8 +802,8 @@ static void sanei_xml_set_hex_attr(xmlNode* node, const char* attr_name,
   xmlNewProp(node, (const xmlChar*)attr_name, (const xmlChar*)buf);
 }
 
-static void sanei_xml_set_uint_attr(xmlNode* node, const char* attr_name,
-                                    unsigned attr_value)
+void sanei_xml_set_uint_attr(xmlNode* node, const char* attr_name,
+                             unsigned attr_value)
 {
   const int buf_size = 128;
   char buf[buf_size];
@@ -811,8 +811,8 @@ static void sanei_xml_set_uint_attr(xmlNode* node, const char* attr_name,
   xmlNewProp(node, (const xmlChar*)attr_name, (const xmlChar*)buf);
 }
 
-static xmlNode* sanei_xml_append_command(xmlNode* sibling,
-                                         int indent, xmlNode* e_command)
+xmlNode* sanei_xml_append_command(xmlNode* sibling,
+                                  int indent, xmlNode* e_command)
 {
   if (indent)
     {
@@ -831,7 +831,7 @@ static void sanei_xml_command_common_props(xmlNode* node, int endpoint_number,
   xmlNewProp(node, (const xmlChar*)"direction", (const xmlChar*)direction);
 }
 
-static void sanei_xml_record_seq(xmlNode* node)
+void sanei_xml_record_seq(xmlNode* node)
 {
   int seq = sanei_xml_get_prop_uint(node, "seq");
   if (seq > 0)
@@ -842,7 +842,7 @@ static void sanei_xml_break()
 {
 }
 
-static void sanei_xml_break_if_needed(xmlNode* node)
+void sanei_xml_break_if_needed(xmlNode* node)
 {
   char* attr = sanei_xml_get_prop(node, "debug_break");
   if (attr != NULL)
@@ -853,8 +853,8 @@ static void sanei_xml_break_if_needed(xmlNode* node)
 }
 
 // returns 1 on success
-static int sanei_usb_check_attr(xmlNode* node, const char* attr_name,
-                                const char* expected, const char* parent_fun)
+int sanei_usb_check_attr(xmlNode* node, const char* attr_name,
+                         const char* expected, const char* parent_fun)
 {
   char* attr = sanei_xml_get_prop(node, attr_name);
   if (attr == NULL)