[gtk/wip/otte/listview: 903/1040] sorter: Add tests

[Benjamin Otte <otte src gnome org>]

commit eed3989320ce4961e1e57aae964771bec0cbbdd1
Author: Matthias Clasen <mclasen redhat com>
Date:   Wed Dec 4 19:18:50 2019 -0500

    sorter: Add tests
    
    Some basic tests for GtkSorter.

 testsuite/gtk/meson.build |   1 +
 testsuite/gtk/sorter.c    | 671 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 672 insertions(+)
---
diff --git a/testsuite/gtk/meson.build b/testsuite/gtk/meson.build
index bb4f70eaea..4746b37cf0 100644
--- a/testsuite/gtk/meson.build
+++ b/testsuite/gtk/meson.build
@@ -54,6 +54,7 @@ tests = [
   ['searchbar'],
   ['singleselection'],
   ['slicelistmodel'],
+  ['sorter'],
   ['sortlistmodel'],
   ['spinbutton'],
   ['stylecontext'],
diff --git a/testsuite/gtk/sorter.c b/testsuite/gtk/sorter.c
new file mode 100644
index 0000000000..2dafedebae
--- /dev/null
+++ b/testsuite/gtk/sorter.c
@@ -0,0 +1,671 @@
+/* GtkSorter tests.
+ *
+ * Copyright (C) 2019, Red Hat, Inc.
+ * Authors: Benjamin Otte <otte gnome org>
+ *          Matthias Clasen <mclasen redhat com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <locale.h>
+
+#include <gtk/gtk.h>
+
+static GQuark number_quark;
+
+static guint
+get_number (GObject *object)
+{
+  return GPOINTER_TO_UINT (g_object_get_qdata (object, number_quark));
+}
+
+static guint
+get (GListModel *model,
+     guint       position)
+{
+  GObject *object = g_list_model_get_item (model, position);
+  guint number;
+  g_assert (object != NULL);
+  number = get_number (object);
+  g_object_unref (object);
+  return number;
+}
+
+static char *
+get_string (gpointer object)
+{
+  return g_strdup_printf ("%u", GPOINTER_TO_UINT (g_object_get_qdata (object, number_quark)));
+}
+
+static guint
+get_number_mod_5 (GObject *object)
+{
+  return get_number (object) % 5;
+}
+
+static void
+append_digit (GString *s,
+              guint    digit)
+{
+  static char *names[10] = { NULL, "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" };
+
+  if (digit == 0)
+    return;
+
+  g_assert (digit < 10);
+
+  if (s->len)
+    g_string_append_c (s, ' ');
+  g_string_append (s, names[digit]);
+}
+
+static void
+append_below_thousand (GString *s,
+                       guint    n)
+{
+  if (n >= 100)
+    {
+      append_digit (s, n / 100);
+      g_string_append (s, " hundred");
+      n %= 100;
+    }
+
+  if (n >= 20)
+    {
+      const char *names[10] = { NULL, NULL, "twenty", "thirty", "fourty", "fifty", "sixty", "seventy", 
"eighty", "ninety" };
+      if (s->len)
+        g_string_append_c (s, ' ');
+      g_string_append (s, names [n / 10]);
+      n %= 10;
+    }
+
+  if (n >= 10)
+    {
+      const char *names[10] = { "ten", "eleven", "twelve", "thirteen", "fourteen",
+                                "fifteen", "sixteen", "seventeen", "eighteen", "nineteen" };
+      if (s->len)
+        g_string_append_c (s, ' ');
+      g_string_append (s, names [n - 10]);
+    }
+  else
+    {
+      append_digit (s, n);
+    }
+}
+
+static char *
+get_spelled_out (gpointer object)
+{
+  guint n = GPOINTER_TO_UINT (g_object_get_qdata (object, number_quark));
+  GString *s;
+
+  g_assert (n < 1000000);
+
+  if (n == 0)
+    return g_strdup ("Zero");
+
+  s = g_string_new (NULL);
+
+  if (n >= 1000)
+    {
+      append_below_thousand (s, n / 1000);
+      g_string_append (s, " thousand");
+      n %= 1000;
+    }
+
+  append_below_thousand (s, n);
+
+  /* Capitalize first letter so we can do case-sensitive sorting */
+  s->str[0] = g_ascii_toupper (s->str[0]);
+
+  return g_string_free (s, FALSE);
+}
+
+static char *
+model_to_string (GListModel *model)
+{
+  GString *string = g_string_new (NULL);
+  guint i;
+
+  for (i = 0; i < g_list_model_get_n_items (model); i++)
+    {
+      if (i > 0)
+        g_string_append (string, " ");
+      g_string_append_printf (string, "%u", get (model, i));
+    }
+
+  return g_string_free (string, FALSE);
+}
+
+static GListStore *
+new_store (guint start,
+           guint end,
+           guint step);
+
+static void
+add (GListStore *store,
+     guint       number)
+{
+  GObject *object;
+
+  /* 0 cannot be differentiated from NULL, so don't use it */
+  g_assert (number != 0);
+
+  object = g_object_new (G_TYPE_OBJECT, NULL);
+  g_object_set_qdata (object, number_quark, GUINT_TO_POINTER (number));
+  g_list_store_append (store, object);
+  g_object_unref (object);
+}
+
+#define assert_model(model, expected) G_STMT_START{ \
+  char *s = model_to_string (G_LIST_MODEL (model)); \
+  if (!g_str_equal (s, expected)) \
+     g_assertion_message_cmpstr (G_LOG_DOMAIN, __FILE__, __LINE__, G_STRFUNC, \
+         #model " == " #expected, s, "==", expected); \
+  g_free (s); \
+}G_STMT_END
+
+#define assert_not_model(model, expected) G_STMT_START{ \
+  char *s = model_to_string (G_LIST_MODEL (model)); \
+  if (g_str_equal (s, expected)) \
+     g_assertion_message_cmpstr (G_LOG_DOMAIN, __FILE__, __LINE__, G_STRFUNC, \
+         #model " != " #expected, s, "!=", expected); \
+  g_free (s); \
+}G_STMT_END
+
+/* This could be faster by foreach()ing through the models and comparing
+ * the item pointers */
+#define assert_model_equal(model1, model2) G_STMT_START{\
+  char *s1 = model_to_string (G_LIST_MODEL (model1)); \
+  char *s2 = model_to_string (G_LIST_MODEL (model2)); \
+  if (!g_str_equal (s1, s2)) \
+     g_assertion_message_cmpstr (G_LOG_DOMAIN, __FILE__, __LINE__, G_STRFUNC, \
+         #model1 " != " #model2, s1, "==", s2); \
+  g_free (s2); \
+  g_free (s1); \
+}G_STMT_END
+
+static GListStore *
+new_empty_store (void)
+{
+  return g_list_store_new (G_TYPE_OBJECT);
+}
+
+static GListStore *
+new_store (guint start,
+           guint end,
+           guint step)
+{
+  GListStore *store = new_empty_store ();
+  guint i;
+
+  for (i = start; i <= end; i += step)
+    add (store, i);
+
+  return store;
+}
+
+static GListStore *
+fisher_yates_shuffle (GListStore *store)
+{
+  int i, n;
+  gboolean shuffled = FALSE;
+
+  while (!shuffled)
+    {
+      n = g_list_model_get_n_items (G_LIST_MODEL (store));
+      for (i = 0; i < n; i++)
+        {
+          int pos = g_random_int_range (0, n - i);
+          GObject *item;
+
+          item = g_list_model_get_item (G_LIST_MODEL (store), pos);
+          g_list_store_remove (store, pos);
+          g_list_store_append (store, item);
+          g_object_unref (item); 
+          shuffled |= pos != 0;
+        }
+    }
+
+  return store;
+}
+
+static GtkSortListModel *
+new_model (guint      size,
+           GtkSorter *sorter)
+{
+  GtkSortListModel *result;
+
+  result = gtk_sort_list_model_new (G_LIST_MODEL (fisher_yates_shuffle (new_store (1, size, 1))), sorter);
+
+  return result;
+}
+
+static int
+compare_numbers (gconstpointer item1,
+                 gconstpointer item2,
+                 gpointer data)
+{
+  guint n1 = get_number (G_OBJECT (item1));
+  guint n2 = get_number (G_OBJECT (item2));
+
+  return n1 - n2;
+}
+
+static void
+test_simple (void)
+{
+  GtkSortListModel *model;
+  GtkSorter *sorter;
+
+  model = new_model (20, NULL);
+  assert_not_model (model, "1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20");
+
+  sorter = gtk_custom_sorter_new (compare_numbers, NULL, NULL);
+  gtk_sort_list_model_set_sorter (model, sorter);
+  g_object_unref (sorter);
+
+  assert_model (model, "1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20");
+
+  gtk_sort_list_model_set_sorter (model, NULL);
+  assert_not_model (model, "1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20");
+
+  g_object_unref (model);
+}
+
+static void
+test_string (void)
+{
+  GtkSortListModel *model;
+  GtkSorter *sorter;
+  GtkExpression *expression;
+
+  model = new_model (20, NULL);
+  assert_not_model (model, "1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20");
+
+  sorter = gtk_string_sorter_new (gtk_cclosure_expression_new (G_TYPE_STRING, NULL, 0, NULL, 
(GCallback)get_string, NULL, NULL));
+
+  gtk_sort_list_model_set_sorter (model, sorter);
+  g_object_unref (sorter);
+
+  assert_model (model, "1 10 11 12 13 14 15 16 17 18 19 2 20 3 4 5 6 7 8 9");
+
+  expression = gtk_cclosure_expression_new (G_TYPE_STRING, NULL, 0, NULL, (GCallback)get_spelled_out, NULL, 
NULL);
+  gtk_string_sorter_set_expression (GTK_STRING_SORTER (sorter), expression);
+  gtk_expression_unref (expression);
+
+  assert_model (model, "8 18 11 15 5 4 14 9 19 1 7 17 6 16 10 13 3 12 20 2");
+
+  gtk_string_sorter_set_expression (GTK_STRING_SORTER (sorter), NULL);
+  assert_not_model (model, "1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20");
+
+  g_object_unref (model);
+}
+
+static void
+inc_counter (GtkSorter *sorter, int change, gpointer data)
+{
+  int *counter = data;
+
+  (*counter)++;
+}
+
+static void
+test_change (void)
+{
+  GtkSorter *sorter;
+  GtkExpression *expression;
+  int counter = 0;
+
+  sorter = gtk_string_sorter_new (NULL);
+  g_signal_connect (sorter, "changed", G_CALLBACK (inc_counter), &counter);
+
+  expression = gtk_cclosure_expression_new (G_TYPE_STRING, NULL, 0, NULL, (GCallback)get_string, NULL, NULL);
+  gtk_string_sorter_set_expression (GTK_STRING_SORTER (sorter), expression);
+  g_assert_cmpint (counter, ==, 1);
+
+  gtk_string_sorter_set_expression (GTK_STRING_SORTER (sorter), expression);
+  g_assert_cmpint (counter, ==, 1);
+  
+  gtk_expression_unref (expression);
+
+  gtk_string_sorter_set_ignore_case (GTK_STRING_SORTER (sorter), FALSE);
+  g_assert_cmpint (counter, ==, 2);
+
+  gtk_string_sorter_set_ignore_case (GTK_STRING_SORTER (sorter), FALSE);
+  g_assert_cmpint (counter, ==, 2);
+
+  g_object_unref (sorter);
+}
+
+static void
+test_numeric (void)
+{
+  GtkSortListModel *model;
+  GtkSorter *sorter;
+
+  model = new_model (20, NULL);
+  assert_not_model (model, "1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20");
+
+  sorter = gtk_numeric_sorter_new (gtk_cclosure_expression_new (G_TYPE_UINT, NULL, 0, NULL, 
(GCallback)get_number, NULL, NULL));
+  gtk_sort_list_model_set_sorter (model, sorter);
+  assert_model (model, "1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20");
+
+  gtk_numeric_sorter_set_sort_order (GTK_NUMERIC_SORTER (sorter), GTK_SORT_DESCENDING);
+  assert_model (model, "20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1");
+
+  gtk_numeric_sorter_set_sort_order (GTK_NUMERIC_SORTER (sorter), GTK_SORT_ASCENDING);
+  assert_model (model, "1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20");
+
+  gtk_numeric_sorter_set_expression (GTK_NUMERIC_SORTER (sorter), NULL);
+  assert_not_model (model, "1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20");
+
+  g_object_unref (sorter);
+  g_object_unref (model);
+}
+
+/* sort even numbers before odd, don't care about anything else */
+static int
+compare_even (gconstpointer item1,
+              gconstpointer item2,
+              gpointer data)
+{
+  guint n1 = get_number (G_OBJECT (item1));
+  guint n2 = get_number (G_OBJECT (item2));
+  int r1 = n1 % 2;
+  int r2 = n2 % 2;
+
+  if (r1 == r2)
+    return 0;
+
+  if (r1 == 1)
+    return 1;
+
+  return -1;
+}
+
+static void
+test_multi (void)
+{
+  GtkSortListModel *model;
+  GtkSorter *sorter;
+  GtkSorter *sorter1;
+  GtkSorter *sorter2;
+  GtkExpression *expression;
+
+  model = new_model (20, NULL);
+  assert_not_model (model, "1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20");
+
+  sorter2 = gtk_numeric_sorter_new (NULL);
+  gtk_sort_list_model_set_sorter (model, sorter2);
+  expression = gtk_cclosure_expression_new (G_TYPE_UINT, NULL, 0, NULL, (GCallback)get_number, NULL, NULL);
+  gtk_numeric_sorter_set_expression (GTK_NUMERIC_SORTER (sorter2), expression);
+  gtk_expression_unref (expression);
+
+  assert_model (model, "1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20");
+
+  sorter = gtk_multi_sorter_new ();
+  gtk_sort_list_model_set_sorter (model, sorter);
+
+  sorter1 = gtk_custom_sorter_new (compare_even, NULL, NULL);
+  gtk_multi_sorter_append (GTK_MULTI_SORTER (sorter), sorter1);
+  gtk_multi_sorter_append (GTK_MULTI_SORTER (sorter), sorter2);
+
+  assert_model (model, "2 4 6 8 10 12 14 16 18 20 1 3 5 7 9 11 13 15 17 19");
+
+  /* This doesn't do anything */
+  gtk_multi_sorter_remove (GTK_MULTI_SORTER (sorter), 12345);
+  assert_model (model, "2 4 6 8 10 12 14 16 18 20 1 3 5 7 9 11 13 15 17 19");
+
+  gtk_multi_sorter_remove (GTK_MULTI_SORTER (sorter), 0);
+  assert_model (model, "1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20");
+
+  gtk_multi_sorter_remove (GTK_MULTI_SORTER (sorter), 0);
+  assert_not_model (model, "1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20");
+
+  g_object_unref (model);
+  g_object_unref (sorter);
+}
+
+/* Check that the multi sorter properly disconnects its changed signal */
+static void
+test_multi_destruct (void)
+{
+  GtkSorter *multi, *sorter;
+
+  multi = gtk_multi_sorter_new ();
+  sorter = gtk_numeric_sorter_new (gtk_cclosure_expression_new (G_TYPE_UINT, NULL, 0, NULL, 
(GCallback)get_number, NULL, NULL));
+  gtk_multi_sorter_append (GTK_MULTI_SORTER (multi), g_object_ref (sorter));
+  g_object_unref (multi);
+
+  gtk_numeric_sorter_set_sort_order (GTK_NUMERIC_SORTER (sorter), GTK_SORT_DESCENDING);
+  g_object_unref (sorter);
+}
+
+static void
+test_multi_changes (void)
+{
+  GtkSortListModel *model;
+  GtkSorter *multi;
+  GtkSorter *sorter1;
+  GtkSorter *sorter2;
+  GtkSorter *sorter3;
+  GtkExpression *expression;
+  int counter = 0;
+
+  /* We want a sorted model, so that we can be sure partial sorts do the right thing */
+  model = gtk_sort_list_model_new (G_LIST_MODEL (new_store (1, 20, 1)), NULL);
+  assert_model (model, "1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20");
+
+  multi = gtk_multi_sorter_new ();
+  g_signal_connect (multi, "changed", G_CALLBACK (inc_counter), &counter);
+  gtk_sort_list_model_set_sorter (model, multi);
+  assert_model (model, "1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20");
+  g_assert_cmpint (counter, ==, 0);
+
+  sorter1 = gtk_numeric_sorter_new (NULL);
+  gtk_multi_sorter_append (GTK_MULTI_SORTER (multi), sorter1);
+  assert_model (model, "1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20");
+  g_assert_cmpint (counter, ==, 1);
+
+  expression = gtk_cclosure_expression_new (G_TYPE_UINT, NULL, 0, NULL, (GCallback)get_number_mod_5, NULL, 
NULL);
+  gtk_numeric_sorter_set_expression (GTK_NUMERIC_SORTER (sorter1), expression);
+  gtk_expression_unref (expression);
+  assert_model (model, "5 10 15 20 1 6 11 16 2 7 12 17 3 8 13 18 4 9 14 19");
+  g_assert_cmpint (counter, ==, 2);
+
+  gtk_numeric_sorter_set_sort_order (GTK_NUMERIC_SORTER (sorter1), GTK_SORT_DESCENDING);
+  assert_model (model, "4 9 14 19 3 8 13 18 2 7 12 17 1 6 11 16 5 10 15 20");
+  g_assert_cmpint (counter, ==, 3);
+
+  sorter2 = gtk_custom_sorter_new (compare_even, NULL, NULL);
+  gtk_multi_sorter_append (GTK_MULTI_SORTER (multi), sorter2);
+  assert_model (model, "4 14 9 19 8 18 3 13 2 12 7 17 6 16 1 11 10 20 5 15");
+  g_assert_cmpint (counter, ==, 4);
+
+  gtk_numeric_sorter_set_sort_order (GTK_NUMERIC_SORTER (sorter1), GTK_SORT_ASCENDING);
+  assert_model (model, "10 20 5 15 6 16 1 11 2 12 7 17 8 18 3 13 4 14 9 19");
+  g_assert_cmpint (counter, ==, 5);
+
+  sorter3 = gtk_string_sorter_new (gtk_cclosure_expression_new (G_TYPE_STRING, NULL, 0, NULL, 
(GCallback)get_spelled_out, NULL, NULL));
+  gtk_multi_sorter_append (GTK_MULTI_SORTER (multi), sorter3);
+  assert_model (model, "10 20 15 5 6 16 11 1 12 2 7 17 8 18 13 3 4 14 9 19");
+  g_assert_cmpint (counter, ==, 6);
+
+  gtk_multi_sorter_remove (GTK_MULTI_SORTER (multi), 1);
+  assert_model (model, "15 5 10 20 11 1 6 16 7 17 12 2 8 18 13 3 4 14 9 19");
+  g_assert_cmpint (counter, ==, 7);
+
+  gtk_multi_sorter_remove (GTK_MULTI_SORTER (multi), 1);
+  assert_model (model, "5 10 15 20 1 6 11 16 2 7 12 17 3 8 13 18 4 9 14 19");
+  g_assert_cmpint (counter, ==, 8);
+
+  gtk_multi_sorter_remove (GTK_MULTI_SORTER (multi), 0);
+  assert_model (model, "1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20");
+  g_assert_cmpint (counter, ==, 9);
+
+  g_object_unref (multi);
+  g_object_unref (model);
+}
+
+static GtkSorter *
+even_odd_sorter_new (void)
+{
+  return gtk_custom_sorter_new (compare_even, NULL, NULL);
+}
+
+static GtkSorter *
+numeric_sorter_new (void)
+{
+  return gtk_numeric_sorter_new (gtk_cclosure_expression_new (G_TYPE_UINT, NULL, 0, NULL, 
(GCallback)get_number, NULL, NULL));
+}
+
+static void
+switch_order (GtkSorter *sorter)
+{
+  if (gtk_numeric_sorter_get_sort_order (GTK_NUMERIC_SORTER (sorter)) == GTK_SORT_ASCENDING)
+    gtk_numeric_sorter_set_sort_order (GTK_NUMERIC_SORTER (sorter), GTK_SORT_DESCENDING);
+  else
+    gtk_numeric_sorter_set_sort_order (GTK_NUMERIC_SORTER (sorter), GTK_SORT_ASCENDING);
+}
+
+static void
+set_order_ascending (GtkSorter *sorter)
+{
+  gtk_numeric_sorter_set_sort_order (GTK_NUMERIC_SORTER (sorter), GTK_SORT_ASCENDING);
+}
+
+static void
+set_order_descending (GtkSorter *sorter)
+{
+  gtk_numeric_sorter_set_sort_order (GTK_NUMERIC_SORTER (sorter), GTK_SORT_DESCENDING);
+}
+
+static void
+set_expression_get_number (GtkSorter *sorter)
+{
+  GtkExpression *expression = gtk_cclosure_expression_new (G_TYPE_UINT, NULL, 0, NULL, 
(GCallback)get_number, NULL, NULL);
+  gtk_numeric_sorter_set_expression (GTK_NUMERIC_SORTER (sorter), expression);
+  gtk_expression_unref (expression);
+}
+
+static void
+set_expression_get_number_mod_5 (GtkSorter *sorter)
+{
+  GtkExpression *expression = gtk_cclosure_expression_new (G_TYPE_UINT, NULL, 0, NULL, 
(GCallback)get_number, NULL, NULL);
+  gtk_numeric_sorter_set_expression (GTK_NUMERIC_SORTER (sorter), expression);
+  gtk_expression_unref (expression);
+}
+
+static void
+modify_sorter (GtkSorter *multi)
+{
+  struct {
+    GType type;
+    GtkSorter * (* create_func) (void);
+    void (* modify_func) (GtkSorter *);
+  } options[] = {
+    { GTK_TYPE_CUSTOM_SORTER, even_odd_sorter_new, NULL },
+    { GTK_TYPE_NUMERIC_SORTER, numeric_sorter_new, switch_order },
+    { GTK_TYPE_NUMERIC_SORTER, numeric_sorter_new, set_order_ascending },
+    { GTK_TYPE_NUMERIC_SORTER, numeric_sorter_new, set_order_descending },
+    { GTK_TYPE_NUMERIC_SORTER, numeric_sorter_new, set_expression_get_number, },
+    { GTK_TYPE_NUMERIC_SORTER, numeric_sorter_new, set_expression_get_number_mod_5, }
+  };
+  GtkSorter *current;
+  guint option;
+
+  current = g_list_model_get_item (G_LIST_MODEL (multi), 0);
+  option = g_random_int_range (0, G_N_ELEMENTS (options));
+
+  if (current == NULL || options[option].type != G_OBJECT_TYPE (current) || options[option].modify_func == 
NULL)
+    {
+      g_clear_object (&current);
+      gtk_multi_sorter_remove (GTK_MULTI_SORTER (multi), 0);
+      
+      current = options[option].create_func ();
+      if (options[option].modify_func)
+        options[option].modify_func (current);
+
+      gtk_multi_sorter_append (GTK_MULTI_SORTER (multi), current);
+    }
+  else
+    {
+      options[option].modify_func (current);
+    }
+}
+
+static void
+test_stable (void)
+{
+  GtkSortListModel *model1, *model2, *model2b;
+  GtkSorter *multi, *a, *b;
+  guint i;
+
+  a = gtk_multi_sorter_new ();
+  b = gtk_multi_sorter_new ();
+  /* We create 2 setups:
+   * 1. sortmodel (multisorter [a, b])
+   * 2. sortmodel (b) => sortmodel (a)
+   * Given stability of the sort, these 2 setups should always produce the
+   * same results, namely the list should be sorter by a before it's sorted
+   * by b.
+   *
+   * All we do is make a and b random sorters and assert that the 2 setups
+   * produce the same order every time.
+   */
+  multi = gtk_multi_sorter_new ();
+  gtk_multi_sorter_append (GTK_MULTI_SORTER (multi), a);
+  gtk_multi_sorter_append (GTK_MULTI_SORTER (multi), b);
+  model1 = new_model (20, multi);
+  g_object_unref (multi);
+  model2b = gtk_sort_list_model_new (gtk_sort_list_model_get_model (model1), b);
+  model2 = gtk_sort_list_model_new (G_LIST_MODEL (model2b), a);
+  assert_model_equal (model1, model2);
+
+  modify_sorter (a);
+  assert_model_equal (model1, model2);
+  modify_sorter (b);
+  assert_model_equal (model1, model2);
+
+  for (i = 0; i < 100; i++)
+    {
+      modify_sorter (g_random_boolean () ? a : b);
+      assert_model_equal (model1, model2);
+    }
+
+  g_object_unref (model1);
+  g_object_unref (model2);
+  g_object_unref (model2b);
+}
+
+int
+main (int argc, char *argv[])
+{
+  g_test_init (&argc, &argv, NULL);
+  setlocale (LC_ALL, "C");
+
+  number_quark = g_quark_from_static_string ("Like a trashcan fire in a prison cell");
+
+  g_test_add_func ("/sorter/simple", test_simple);
+  g_test_add_func ("/sorter/string", test_string);
+  g_test_add_func ("/sorter/change", test_change);
+  g_test_add_func ("/sorter/numeric", test_numeric);
+  g_test_add_func ("/sorter/multi", test_multi);
+  g_test_add_func ("/sorter/multi-destruct", test_multi_destruct);
+  g_test_add_func ("/sorter/multi-changes", test_multi_changes);
+  g_test_add_func ("/sorter/stable", test_stable);
+
+  return g_test_run ();
+}