diff --git a/test/Makefile.am b/test/Makefile.am
index b89a697c..0a3b5d7f 100644
--- a/test/Makefile.am
+++ b/test/Makefile.am
@@ -4,10 +4,16 @@ AUTOMAKE_OPTIONS = no-dependencies
 
 EXTRA_DIST = notest.c
 
-noinst_PROGRAMS = wtest
+noinst_PROGRAMS = wtest wm_fsm_test
 
 wtest_SOURCES = wtest.c
 
 wtest_LDADD = $(top_builddir)/wmlib/libWMaker.la @XLFLAGS@ @XLIBS@
 
 AM_CPPFLAGS = -g -D_BSD_SOURCE @XCFLAGS@ -I$(top_srcdir)/wmlib
+
+wm_fsm_test_SOURCES = wm_fsm_test.c
+
+wm_fsm_test_CPPFLAGS = $(shell pkg-config --cflags gtk+-3.0)
+
+wm_fsm_test_LDFLAGS = $(shell pkg-config --libs gtk+-3.0) -lX11
diff --git a/test/wm_fsm_test.c b/test/wm_fsm_test.c
new file mode 100644
index 00000000..027c6b08
--- /dev/null
+++ b/test/wm_fsm_test.c
@@ -0,0 +1,136 @@
+/* test application that demonstrates _NET_WM_FULLSCREEN_MONITORS 
+ *
+ * how to run it:
+ * G_MESSAGES_DEBUG=all ./wm_fsm_test
+ */
+
+#include <gtk/gtk.h>
+#include <gdk/gdkx.h>
+#include <string.h>
+
+
+static GtkWidget* window;
+
+static gboolean print_final_size(gpointer data)
+{
+   (void)data;
+   gint w, h;
+   gtk_window_get_size(GTK_WINDOW(window), &w, &h);
+   g_debug("final window size: %dx%d", w, h);
+   return FALSE;
+}
+
+static gboolean on_configure_after_unfullscreen(GtkWidget *widget, GdkEventConfigure *event, gpointer data)
+{
+   (void)event;
+   (void)data;
+   g_signal_handlers_disconnect_by_func(widget, on_configure_after_unfullscreen, data);
+   g_idle_add(print_final_size, NULL);
+   return FALSE;
+}
+
+static gboolean fullscreen(gpointer data)
+{
+   (void)data;
+   g_debug("fullscreen()");
+   gtk_window_fullscreen(GTK_WINDOW(window));
+   return FALSE;
+}
+
+static gboolean on_window_state_event(GtkWidget *widget, GdkEventWindowState *event, gpointer data)
+{
+   (void)widget;
+   (void)data;
+   if ((event->changed_mask & GDK_WINDOW_STATE_FULLSCREEN) &&
+       !(event->new_window_state & GDK_WINDOW_STATE_FULLSCREEN)) {
+      /* Force geometry back */
+      gtk_window_move(GTK_WINDOW(window), 0, 0);
+      gtk_window_resize(GTK_WINDOW(window), 800, 600);
+      g_signal_connect(window, "configure-event", G_CALLBACK(on_configure_after_unfullscreen), NULL);
+   }
+   return FALSE;
+}
+
+static gboolean unfullscreen(gpointer data)
+{
+   (void)data;
+   g_debug("unfullscreen()");
+   gtk_window_unfullscreen(GTK_WINDOW(window));
+   return FALSE;
+}
+
+static gboolean switch_monitors(gpointer data)
+{
+   static const long monitors[4][4] = {
+      {0, 0, 0, 1},
+      {0, 0, 0, 0},
+      {1, 1, 1, 1},
+      {0, 0, 0, 1}
+   };
+
+   static const char* desc[4] = {
+       "Window should be covering both heads 1 and 2\n",
+       "Window should be covering just the first head\n",
+       "Window should be covering just the second head\n",
+       "Window should be covering both heads 1 and 2\n"
+   };
+
+
+   guint index = GPOINTER_TO_UINT(data);
+
+   g_debug("%s", desc[index]);
+
+   GdkDisplay *display = gdk_display_get_default();
+   GdkWindow *gwin = gtk_widget_get_window(window);
+   if (!gwin) {
+      g_warning("switch_monitors: window not realized yet");
+      return FALSE;
+   }
+   XClientMessageEvent xclient;
+
+   memset(&xclient, 0, sizeof(xclient));
+   xclient.type = ClientMessage;
+   xclient.window = GDK_WINDOW_XID(gwin);
+   xclient.message_type = gdk_x11_get_xatom_by_name_for_display(display, "_NET_WM_FULLSCREEN_MONITORS");
+   xclient.format = 32;
+   xclient.data.l[0] = monitors[index][0];
+   xclient.data.l[1] = monitors[index][1];
+   xclient.data.l[2] = monitors[index][2];
+   xclient.data.l[3] = monitors[index][3];
+   xclient.data.l[4] = 1;
+
+   XSendEvent(GDK_WINDOW_XDISPLAY(gwin),
+              GDK_WINDOW_XID(gdk_get_default_root_window()),
+              False,
+              SubstructureRedirectMask | SubstructureNotifyMask,
+              (XEvent *) &xclient);
+
+   return FALSE;
+}
+
+static gboolean quit(gpointer data)
+{
+   (void)data;
+   gtk_main_quit();
+   return FALSE;
+}
+
+int main(int argc, char** argv)
+{
+   gtk_init(&argc, &argv);
+
+   window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
+   gtk_window_set_default_size(GTK_WINDOW(window), 800, 600);
+   gtk_widget_show(window);
+   g_signal_connect(window, "window-state-event", G_CALLBACK(on_window_state_event), NULL);
+
+   g_timeout_add(1000, (GSourceFunc) fullscreen, NULL);
+   g_timeout_add(5000, (GSourceFunc) switch_monitors, GUINT_TO_POINTER(0));
+   g_timeout_add(10000, (GSourceFunc) switch_monitors, GUINT_TO_POINTER(1));
+   g_timeout_add(15000, (GSourceFunc) switch_monitors, GUINT_TO_POINTER(2));
+   g_timeout_add(20000, (GSourceFunc) switch_monitors, GUINT_TO_POINTER(3));
+   g_timeout_add(25000, (GSourceFunc) unfullscreen, NULL);
+   g_timeout_add(30000, (GSourceFunc) quit, NULL);
+
+   gtk_main();
+}