diff --git a/testcases/t/00-load.t b/testcases/t/000-load-deps.t
similarity index 100%
rename from testcases/t/00-load.t
rename to testcases/t/000-load-deps.t
diff --git a/testcases/t/01-tile.t b/testcases/t/001-tile.t
similarity index 100%
rename from testcases/t/01-tile.t
rename to testcases/t/001-tile.t
diff --git a/testcases/t/002-i3-sync.t b/testcases/t/002-i3-sync.t
new file mode 100644
index 00000000..7518c949
--- /dev/null
+++ b/testcases/t/002-i3-sync.t
@@ -0,0 +1,15 @@
+#!perl
+# vim:ts=4:sw=4:expandtab
+#
+# checks if i3 supports I3_SYNC
+#
+use X11::XCB qw(:all);
+use X11::XCB::Connection;
+use i3test;
+
+my $x = X11::XCB::Connection->new;
+
+my $result = sync_with_i3($x);
+ok($result, 'syncing was successful');
+
+done_testing;
diff --git a/testcases/t/05-ipc.t b/testcases/t/003-ipc.t
similarity index 100%
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rename to testcases/t/003-ipc.t
diff --git a/testcases/t/03-unmanaged.t b/testcases/t/004-unmanaged.t
similarity index 100%
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rename to testcases/t/004-unmanaged.t
diff --git a/testcases/t/04-floating.t b/testcases/t/005-floating.t
similarity index 100%
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diff --git a/testcases/t/02-fullscreen.t b/testcases/t/100-fullscreen.t
similarity index 100%
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diff --git a/testcases/t/06-focus.t b/testcases/t/101-focus.t
similarity index 100%
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rename to testcases/t/101-focus.t
diff --git a/testcases/t/10-dock.t b/testcases/t/102-dock.t
similarity index 100%
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rename to testcases/t/102-dock.t
diff --git a/testcases/t/07-move.t b/testcases/t/103-move.t
similarity index 100%
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rename to testcases/t/103-move.t
diff --git a/testcases/t/08-focus-stack.t b/testcases/t/104-focus-stack.t
similarity index 100%
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diff --git a/testcases/t/09-stacking.t b/testcases/t/105-stacking.t
similarity index 100%
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diff --git a/testcases/t/11-goto.t b/testcases/t/111-goto.t
similarity index 100%
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diff --git a/testcases/t/12-floating-resize.t b/testcases/t/112-floating-resize.t
similarity index 100%
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diff --git a/testcases/t/13-urgent.t b/testcases/t/113-urgent.t
similarity index 100%
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diff --git a/testcases/t/14-client-leader.t b/testcases/t/114-client-leader.t
similarity index 100%
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rename to testcases/t/114-client-leader.t
diff --git a/testcases/t/15-ipc-workspaces.t b/testcases/t/115-ipc-workspaces.t
similarity index 100%
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rename to testcases/t/115-ipc-workspaces.t
diff --git a/testcases/t/16-nestedcons.t b/testcases/t/116-nestedcons.t
similarity index 100%
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diff --git a/testcases/t/17-workspace.t b/testcases/t/117-workspace.t
similarity index 100%
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rename to testcases/t/117-workspace.t
diff --git a/testcases/t/18-openkill.t b/testcases/t/118-openkill.t
similarity index 100%
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diff --git a/testcases/t/19-match.t b/testcases/t/119-match.t
similarity index 100%
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rename to testcases/t/119-match.t
diff --git a/testcases/t/20-multiple-cmds.t b/testcases/t/120-multiple-cmds.t
similarity index 100%
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rename to testcases/t/120-multiple-cmds.t
diff --git a/testcases/t/21-next-prev.t b/testcases/t/121-next-prev.t
similarity index 100%
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rename to testcases/t/121-next-prev.t
diff --git a/testcases/t/22-split.t b/testcases/t/122-split.t
similarity index 100%
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diff --git a/testcases/t/24-move.t b/testcases/t/124-move.t
similarity index 100%
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diff --git a/testcases/t/26-regress-close.t b/testcases/t/126-regress-close.t
similarity index 100%
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rename to testcases/t/126-regress-close.t
diff --git a/testcases/t/27-regress-floating-parent.t b/testcases/t/127-regress-floating-parent.t
similarity index 100%
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diff --git a/testcases/t/28-open-order.t b/testcases/t/128-open-order.t
similarity index 100%
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diff --git a/testcases/t/29-focus-after-close.t b/testcases/t/129-focus-after-close.t
similarity index 100%
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diff --git a/testcases/t/30-close-empty-split.t b/testcases/t/130-close-empty-split.t
similarity index 100%
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rename to testcases/t/130-close-empty-split.t
diff --git a/testcases/t/31-stacking-order.t b/testcases/t/131-stacking-order.t
similarity index 100%
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rename to testcases/t/131-stacking-order.t
diff --git a/testcases/t/32-move-workspace.t b/testcases/t/132-move-workspace.t
similarity index 100%
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rename to testcases/t/132-move-workspace.t
diff --git a/testcases/t/33-size-hints.t b/testcases/t/133-size-hints.t
similarity index 100%
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rename to testcases/t/133-size-hints.t
diff --git a/testcases/t/34-invalid-command.t b/testcases/t/134-invalid-command.t
similarity index 100%
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rename to testcases/t/134-invalid-command.t
diff --git a/testcases/t/35-floating-focus.t b/testcases/t/135-floating-focus.t
similarity index 100%
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rename to testcases/t/135-floating-focus.t
diff --git a/testcases/t/36-floating-ws-empty.t b/testcases/t/136-floating-ws-empty.t
similarity index 100%
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diff --git a/testcases/t/37-floating-unmap.t b/testcases/t/137-floating-unmap.t
similarity index 100%
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diff --git a/testcases/t/38-floating-attach.t b/testcases/t/138-floating-attach.t
similarity index 100%
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diff --git a/testcases/t/39-ws-numbers.t b/testcases/t/139-ws-numbers.t
similarity index 100%
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diff --git a/testcases/t/40-focus-lost.t b/testcases/t/140-focus-lost.t
similarity index 100%
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diff --git a/testcases/t/41-resize.t b/testcases/t/141-resize.t
similarity index 100%
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diff --git a/testcases/t/42-regress-move-floating.t b/testcases/t/142-regress-move-floating.t
similarity index 100%
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diff --git a/testcases/t/43-regress-floating-restart.t b/testcases/t/143-regress-floating-restart.t
similarity index 100%
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diff --git a/testcases/t/44-regress-floating-resize.t b/testcases/t/144-regress-floating-resize.t
similarity index 100%
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diff --git a/testcases/t/45-flattening.t b/testcases/t/145-flattening.t
similarity index 100%
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similarity index 100%
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diff --git a/testcases/t/50-regress-dock-restart.t b/testcases/t/150-regress-dock-restart.t
similarity index 100%
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similarity index 100%
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similarity index 100%
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similarity index 100%
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diff --git a/testcases/t/54-regress-multiple-dock.t b/testcases/t/154-regress-multiple-dock.t
similarity index 100%
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diff --git a/testcases/t/55-floating-split-size.t b/testcases/t/155-floating-split-size.t
similarity index 100%
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diff --git a/testcases/t/56-fullscreen-focus.t b/testcases/t/156-fullscreen-focus.t
similarity index 100%
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diff --git a/testcases/t/57-regress-fullscreen-level-up.t b/testcases/t/157-regress-fullscreen-level-up.t
similarity index 100%
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diff --git a/testcases/t/58-wm_take_focus.t b/testcases/t/158-wm_take_focus.t
similarity index 100%
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diff --git a/testcases/t/59-socketpaths.t b/testcases/t/159-socketpaths.t
similarity index 100%
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rename to testcases/t/159-socketpaths.t
diff --git a/testcases/t/61-regress-borders-restart.t b/testcases/t/161-regress-borders-restart.t
similarity index 100%
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diff --git a/testcases/t/62-regress-dock-urgent.t b/testcases/t/162-regress-dock-urgent.t
similarity index 100%
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diff --git a/testcases/t/63-wm-state.t b/testcases/t/163-wm-state.t
similarity index 100%
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diff --git a/testcases/t/64-kill-win-vs-client.t b/testcases/t/164-kill-win-vs-client.t
similarity index 100%
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diff --git a/testcases/t/65-for_window.t b/testcases/t/165-for_window.t
similarity index 100%
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similarity index 100%
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diff --git a/testcases/t/67-workspace_layout.t b/testcases/t/167-workspace_layout.t
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