diff --git a/testsuite/gsk/curve-special-cases.c b/testsuite/gsk/curve-special-cases.c
index 47ae8d211ae82e1034baee2b8b1835a4d0a370ec..2a249da856b1dd37eb3222195938d6e8c28cc7c2 100644
--- a/testsuite/gsk/curve-special-cases.c
+++ b/testsuite/gsk/curve-special-cases.c
@@ -97,7 +97,7 @@ pathop_cb (GskPathOperation        op,
 {
   GskCurve *curve = user_data;
 
-  g_assert (op != GSK_PATH_CLOSE);
+  g_assert_true (op != GSK_PATH_CLOSE);
 
   if (op == GSK_PATH_MOVE)
     return TRUE;
diff --git a/testsuite/gsk/gskrendernodeattach.c b/testsuite/gsk/gskrendernodeattach.c
index 3abf2fdfe22600358885ecc1788fdca547e8a2a0..c1bfb816d0cd6332153475ab8d85ac1ba6b94a4f 100644
--- a/testsuite/gsk/gskrendernodeattach.c
+++ b/testsuite/gsk/gskrendernodeattach.c
@@ -190,7 +190,7 @@ G_GNUC_END_IGNORE_DEPRECATIONS
       {
         GdkSubsurface *subsurface;
 
-        g_assert (gsk_subsurface_node_get_subsurface (node) == NULL);
+        g_assert_null (gsk_subsurface_node_get_subsurface (node));
 
         if (*idx == -1)
           subsurface = gdk_surface_create_subsurface (surface);
diff --git a/testsuite/gsk/misc.c b/testsuite/gsk/misc.c
index 89fa5430a580a92e5684c08ef7fa5acceeb61f80..2038b2cd28b97b54ee6e8c767e682e2a6b96d4e9 100644
--- a/testsuite/gsk/misc.c
+++ b/testsuite/gsk/misc.c
@@ -157,7 +157,7 @@ test_renderer (GskRenderer *renderer)
   GdkSurface *surface;
   GError *error = NULL;
 
-  g_assert (GSK_IS_RENDERER (renderer));
+  g_assert_true (GSK_IS_RENDERER (renderer));
 
   display = gdk_display_open (NULL);
 
diff --git a/testsuite/gsk/replay-node.c b/testsuite/gsk/replay-node.c
index 712abd12ca34e28a0954a3ad089f735100f9706e..4f37658b8d4de8b4dc6948a8b1b045cab16f5584 100644
--- a/testsuite/gsk/replay-node.c
+++ b/testsuite/gsk/replay-node.c
@@ -539,6 +539,6 @@ replay_node (GskRenderNode *node, GtkSnapshot *snapshot)
     case GSK_SUBSURFACE_NODE:
     case GSK_NOT_A_RENDER_NODE:
     default:
-      g_assert (FALSE);
+      g_assert_not_reached ();
     }
 }
diff --git a/testsuite/gtk/builder.c b/testsuite/gtk/builder.c
index 2dfe71a8c26a0e65bda35814075470779b74660c..c7208efe65ee2e494ce9165bb23813713041085c 100644
--- a/testsuite/gtk/builder.c
+++ b/testsuite/gtk/builder.c
@@ -2924,12 +2924,12 @@ builder_object_get_file_property (GtkBuilder  *builder, const gchar *object_id)
   GObject *obj = gtk_builder_get_object (builder, object_id);
   GFile *value = NULL;
 
-  g_assert (obj);
+  g_assert_nonnull (obj);
 
-  g_object_get(obj, "file", &value, NULL);
-  g_assert (value);
+  g_object_get (obj, "file", &value, NULL);
+  g_assert_nonnull (value);
 
-  g_assert (g_type_is_a (G_OBJECT_TYPE (value), G_TYPE_FILE));
+  g_assert_true (g_type_is_a (G_OBJECT_TYPE (value), G_TYPE_FILE));
 
   return value;
 }
@@ -2956,24 +2956,24 @@ test_picture (void)
 
   file_path = builder_object_get_file_property (builder, "relative_path");
   path = g_file_get_path (file_path);
-  g_assert (path);
+  g_assert_nonnull (path);
 
   /* Check path is absolute */
-  g_assert (g_path_is_absolute (path));
+  g_assert_true (g_path_is_absolute (path));
 
   /* Check contents can be loaded */
-  g_assert (g_file_load_contents (file_path, NULL, &contents, NULL, NULL, NULL));
+  g_assert_true (g_file_load_contents (file_path, NULL, &contents, NULL, NULL, NULL));
   g_free (contents);
 
   file_uri = builder_object_get_file_property (builder, "relative_uri");
   uri = g_file_get_uri (file_uri);
-  g_assert (uri);
+  g_assert_nonnull (uri);
 
   /* Check uri is absolute */
-  g_assert (g_str_has_prefix (uri, "file://"));
-  g_assert (g_path_is_absolute (uri + strlen("file://")));
+  g_assert_true (g_str_has_prefix (uri, "file://"));
+  g_assert_true (g_path_is_absolute (uri + strlen("file://")));
 
-  g_assert (g_file_load_contents (file_uri, NULL, &contents, NULL, NULL, NULL));
+  g_assert_true (g_file_load_contents (file_uri, NULL, &contents, NULL, NULL, NULL));
   g_free (contents);
 
   g_object_unref (builder);
diff --git a/testsuite/gtk/maplistmodel.c b/testsuite/gtk/maplistmodel.c
index 16604f7ee283e011896fdf5b27abecbfcdb5a73e..a754f4c16e113f64902a6840006a5a7d21157064 100644
--- a/testsuite/gtk/maplistmodel.c
+++ b/testsuite/gtk/maplistmodel.c
@@ -67,7 +67,7 @@ section_model_to_string (GListModel *model)
   while (i < g_list_model_get_n_items (model))
     {
       gtk_section_model_get_section (GTK_SECTION_MODEL (model), i, &s, &e);
-      g_assert (s == i);
+      g_assert_true (s == i);
 
       if (i > 0)
         g_string_append (string, " ");
diff --git a/testsuite/gtk/slicelistmodel.c b/testsuite/gtk/slicelistmodel.c
index 15e7757b40814276fd3fcb3d2b9e13654b7e6806..d9d3a780675ff894268593b2bc303a31bb315ab3 100644
--- a/testsuite/gtk/slicelistmodel.c
+++ b/testsuite/gtk/slicelistmodel.c
@@ -66,7 +66,7 @@ section_model_to_string (GListModel *model)
   while (i < g_list_model_get_n_items (model))
     {
       gtk_section_model_get_section (GTK_SECTION_MODEL (model), i, &s, &e);
-      g_assert (s == i);
+      g_assert_true (s == i);
 
       if (i > 0)
         g_string_append (string, " ");
diff --git a/testsuite/gtk/sorter.c b/testsuite/gtk/sorter.c
index d878bf62b19df576ccb4438bef743bf9b2238b10..1d0895c7a28fabc589ab9f3852e7076bf93c387b 100644
--- a/testsuite/gtk/sorter.c
+++ b/testsuite/gtk/sorter.c
@@ -390,7 +390,7 @@ check_ascending (GtkSorter  *sorter,
       gpointer item1 = g_list_model_get_item (model, i);
       gpointer item2 = g_list_model_get_item (model, i + 1);
 
-      g_assert (gtk_sorter_compare (sorter, item1, item2) != GTK_ORDERING_LARGER);
+      g_assert_true (gtk_sorter_compare (sorter, item1, item2) != GTK_ORDERING_LARGER);
 
       g_object_unref (item1);
       g_object_unref (item2);
diff --git a/testsuite/gtk/sortlistmodel.c b/testsuite/gtk/sortlistmodel.c
index 42044a0c5fa1b2c1cfb3844d239f94b74f70b8c2..002da5265386160864060da15cebff8c56683f93 100644
--- a/testsuite/gtk/sortlistmodel.c
+++ b/testsuite/gtk/sortlistmodel.c
@@ -67,7 +67,7 @@ section_model_to_string (GListModel *model)
   while (i < g_list_model_get_n_items (model))
     {
       gtk_section_model_get_section (GTK_SECTION_MODEL (model), i, &s, &e);
-      g_assert (s == i);
+      g_assert_true (s == i);
 
       if (i > 0)
         g_string_append (string, " ");
diff --git a/testsuite/reftests/gtk-reftest.c b/testsuite/reftests/gtk-reftest.c
index 2ba47a45932e39150065fc70bd46b954c0c87b9f..349dc2be775636b275622528ea92d0bcc70ff81a 100644
--- a/testsuite/reftests/gtk-reftest.c
+++ b/testsuite/reftests/gtk-reftest.c
@@ -561,15 +561,10 @@ main (int argc, char **argv)
   /* We need to ensure the process' current working directory
    * is the same as the reftest data, because we're using the
    * "file" property of GtkImage as a relative path in builder files.
-   *
-   * The g_assert() is needed to ensure GNU libc does not complain
-   * about the unused return value, and the G_GNUC_UNUSED is needed
-   * to avoid compiler warnings when g_assert() is compiled out
-   * during the release build.
    */
-  int res G_GNUC_UNUSED;
+  int res;
   res = chdir (basedir);
-  g_assert (res == 0);
+  g_assert_true (res == 0);
 
   g_log_set_writer_func (log_writer, NULL, NULL);