Reorder tests to not use the same number (#2947)

Distinct numbers make re-running individual tests easier by helping with
tab-completion.

Completeness verified using:
% for i in $(seq 0 600)
do
  files=$(ls testcases/t/$(printf "%03d" $i)-*.t 2>&- | wc -l)
  [ "$files" != "0" ] && [ "$files" != "1" ] && echo "clash: $i"
done

testcases/t/286-root-window-mouse-binding.t

@@ -0,0 +1,42 @@
+#!perl
+# vim:ts=4:sw=4:expandtab
+#
+# Please read the following documents before working on tests:
+# • http://build.i3wm.org/docs/testsuite.html
+#   (or docs/testsuite)
+#
+# • http://build.i3wm.org/docs/lib-i3test.html
+#   (alternatively: perldoc ./testcases/lib/i3test.pm)
+#
+# • http://build.i3wm.org/docs/ipc.html
+#   (or docs/ipc)
+#
+# • http://onyxneon.com/books/modern_perl/modern_perl_a4.pdf
+#   (unless you are already familiar with Perl)
+#
+# Verifies that mouse bindings work on the root window if
+# --whole-window is set.
+# Ticket: #2115
+use i3test i3_autostart => 0;
+use i3test::XTEST;
+
+my $config = <<EOT;
+# i3 config file (v4)
+font -misc-fixed-medium-r-normal--13-120-75-75-C-70-iso10646-1
+
+workspace_auto_back_and_forth no
+bindsym --whole-window button4 workspace special
+EOT
+
+my $pid = launch_with_config($config);
+fresh_workspace;
+
+xtest_button_press(4, 50, 50);
+xtest_button_release(4, 50, 50);
+sync_with_i3;
+
+is(focused_ws(), 'special', 'the binding was triggered');
+
+exit_gracefully($pid);
+
+done_testing;