diff --git a/testcases/lib/i3test.pm b/testcases/lib/i3test.pm
index d3d8ad04..d1a17865 100644
--- a/testcases/lib/i3test.pm
+++ b/testcases/lib/i3test.pm
@@ -139,7 +139,7 @@ sub wait_for_unmap {
     wait_for_event 2, sub {
         $_[0]->{response_type} == UNMAP_NOTIFY # and $_[0]->{window} == $id
     };
-    sync_with_i3($x);
+    sync_with_i3();
 }
 
 #
@@ -174,7 +174,7 @@ sub open_window {
     $window->map;
     wait_for_map($window);
     # We sync with i3 here to make sure $x->input_focus is updated.
-    sync_with_i3($x);
+    sync_with_i3();
     return $window;
 }
 
@@ -325,8 +325,6 @@ sub focused_ws {
 # See also docs/testsuite for a long explanation
 #
 sub sync_with_i3 {
-    my ($x) = @_;
-
     # Since we need a (mapped) window for receiving a ClientMessage, we create
     # one on the first call of sync_with_i3. It will be re-used in all
     # subsequent calls.
@@ -470,7 +468,7 @@ use parent 'X11::XCB::Connection';
 
 sub input_focus {
     my $self = shift;
-    i3test::sync_with_i3($self);
+    i3test::sync_with_i3();
 
     return $self->SUPER::input_focus(@_);
 }
diff --git a/testcases/t/002-i3-sync.t b/testcases/t/002-i3-sync.t
index 75871f9d..1377ee94 100644
--- a/testcases/t/002-i3-sync.t
+++ b/testcases/t/002-i3-sync.t
@@ -5,7 +5,7 @@
 #
 use i3test;
 
-my $result = sync_with_i3($x);
+my $result = sync_with_i3;
 ok($result, 'syncing was successful');
 
 done_testing;
diff --git a/testcases/t/003-ipc.t b/testcases/t/003-ipc.t
index 477b7163..34359f20 100644
--- a/testcases/t/003-ipc.t
+++ b/testcases/t/003-ipc.t
@@ -17,7 +17,7 @@ my $focus = $x->input_focus;
 # Switch to another workspace
 fresh_workspace;
 
-sync_with_i3($x);
+sync_with_i3;
 my $new_focus = $x->input_focus;
 isnt($focus, $new_focus, "Focus changed");
 
diff --git a/testcases/t/005-floating.t b/testcases/t/005-floating.t
index ac6623f2..6de3ea80 100644
--- a/testcases/t/005-floating.t
+++ b/testcases/t/005-floating.t
@@ -76,7 +76,7 @@ $window->map;
 wait_for_map $window;
 
 cmd 'floating enable';
-sync_with_i3($x);
+sync_with_i3;
 
 ($absolute, $top) = $window->rect;
 
diff --git a/testcases/t/100-fullscreen.t b/testcases/t/100-fullscreen.t
index f5fb6693..dc7eec18 100644
--- a/testcases/t/100-fullscreen.t
+++ b/testcases/t/100-fullscreen.t
@@ -56,7 +56,7 @@ $original_rect = $new_rect;
 
 $window->fullscreen(1);
 
-sync_with_i3($x);
+sync_with_i3;
 
 $new_rect = $window->rect;
 ok(!eq_deeply($new_rect, $original_rect), "Window got repositioned after fullscreen");
@@ -123,7 +123,7 @@ my $swindow = $x->root->create_child(
 
 $swindow->map;
 
-sync_with_i3($x);
+sync_with_i3;
 
 ok(!$swindow->mapped, 'window not mapped while fullscreen window active');
 
@@ -131,12 +131,12 @@ $new_rect = $swindow->rect;
 ok(!eq_deeply($new_rect, $original_rect), "Window got repositioned");
 
 $swindow->fullscreen(1);
-sync_with_i3($x);
+sync_with_i3;
 
 is(fullscreen_windows(), 1, 'amount of fullscreen windows');
 
 $window->fullscreen(0);
-sync_with_i3($x);
+sync_with_i3;
 is(fullscreen_windows(), 0, 'amount of fullscreen windows');
 
 ok($swindow->mapped, 'window mapped after other fullscreen ended');
@@ -148,7 +148,7 @@ ok($swindow->mapped, 'window mapped after other fullscreen ended');
 ###########################################################################
 
 $swindow->fullscreen(0);
-sync_with_i3($x);
+sync_with_i3;
 
 is(fullscreen_windows(), 0, 'amount of fullscreen windows after disabling');
 
diff --git a/testcases/t/101-focus.t b/testcases/t/101-focus.t
index 545b9dd0..8f6038e6 100644
--- a/testcases/t/101-focus.t
+++ b/testcases/t/101-focus.t
@@ -25,7 +25,7 @@ sub focus_after {
     my $msg = shift;
 
     cmd $msg;
-    sync_with_i3 $x;
+    sync_with_i3;
     return $x->input_focus;
 }
 
diff --git a/testcases/t/102-dock.t b/testcases/t/102-dock.t
index ce33f052..20acf49e 100644
--- a/testcases/t/102-dock.t
+++ b/testcases/t/102-dock.t
@@ -52,7 +52,7 @@ is($docknode->{rect}->{height}, 30, 'dock node has unchanged height');
 
 $window->rect(X11::XCB::Rect->new(x => 0, y => 0, width => 50, height => 40));
 
-sync_with_i3 $x;
+sync_with_i3;
 
 @docked = get_dock_clients('top');
 is(@docked, 1, 'one dock client found');
diff --git a/testcases/t/111-goto.t b/testcases/t/111-goto.t
index 5f4d7762..fa9aaf3c 100644
--- a/testcases/t/111-goto.t
+++ b/testcases/t/111-goto.t
@@ -24,7 +24,7 @@ sub focus_after {
     my $msg = shift;
 
     cmd $msg;
-    sync_with_i3($x);
+    sync_with_i3;
     return $x->input_focus;
 }
 
diff --git a/testcases/t/112-floating-resize.t b/testcases/t/112-floating-resize.t
index fe9803e6..ff3a1c04 100644
--- a/testcases/t/112-floating-resize.t
+++ b/testcases/t/112-floating-resize.t
@@ -15,7 +15,7 @@ my $window = open_floating_window;
 my ($a, $t) = $window->rect;
 $window->rect(X11::XCB::Rect->new(x => $a->x, y => $a->y, width => $a->width, height => $a->height));
 
-sync_with_i3($x);
+sync_with_i3;
 
 my ($na, $nt) = $window->rect;
 is_deeply($na, $a, 'Rects are equal after configurerequest');
@@ -23,7 +23,7 @@ is_deeply($na, $a, 'Rects are equal after configurerequest');
 sub test_resize {
     $window->rect(X11::XCB::Rect->new(x => 0, y => 0, width => 100, height => 100));
 
-    sync_with_i3($x);
+    sync_with_i3;
 
     my ($absolute, $top) = $window->rect;
 
@@ -34,7 +34,7 @@ sub test_resize {
 
     $window->rect(X11::XCB::Rect->new(x => 0, y => 0, width => 300, height => 500));
 
-    sync_with_i3($x);
+    sync_with_i3;
 
     ($absolute, $top) = $window->rect;
 
diff --git a/testcases/t/113-urgent.t b/testcases/t/113-urgent.t
index fcfd11e7..5ee61a4d 100644
--- a/testcases/t/113-urgent.t
+++ b/testcases/t/113-urgent.t
@@ -24,7 +24,7 @@ is(@urgent, 0, 'no window got the urgent flag');
 # Add the urgency hint, switch to a different workspace and back again
 #####################################################################
 $top->add_hint('urgency');
-sync_with_i3($x);
+sync_with_i3;
 
 my @content = @{get_ws_content($tmp)};
 @urgent = grep { $_->{urgent} } @content;
@@ -41,7 +41,7 @@ cmd '[id="' . $top->id . '"] focus';
 is(@urgent, 0, 'no window got the urgent flag after focusing');
 
 $top->add_hint('urgency');
-sync_with_i3($x);
+sync_with_i3;
 
 @urgent = grep { $_->{urgent} } @{get_ws_content($tmp)};
 is(@urgent, 0, 'no window got the urgent flag after re-setting urgency hint');
@@ -55,7 +55,7 @@ ok(!$ws->{urgent}, 'urgent flag not set on workspace');
 my $otmp = fresh_workspace;
 
 $top->add_hint('urgency');
-sync_with_i3($x);
+sync_with_i3;
 
 $ws = get_ws($tmp);
 ok($ws->{urgent}, 'urgent flag set on workspace');
diff --git a/testcases/t/119-match.t b/testcases/t/119-match.t
index e2e553f4..2124c02e 100644
--- a/testcases/t/119-match.t
+++ b/testcases/t/119-match.t
@@ -101,7 +101,7 @@ ok(@{$content} == 2, 'two windows opened');
 
 cmd '[class="special" title="left"] kill';
 
-sync_with_i3($x);
+sync_with_i3;
 
 $content = get_ws_content($tmp);
 is(@{$content}, 1, 'one window still there');
diff --git a/testcases/t/133-size-hints.t b/testcases/t/133-size-hints.t
index 34b5e4a5..d3736e3c 100644
--- a/testcases/t/133-size-hints.t
+++ b/testcases/t/133-size-hints.t
@@ -23,7 +23,7 @@ wait_for_map $win;
 $win->hints->aspect($aspect);
 $x->flush;
 
-sync_with_i3($x);
+sync_with_i3;
 
 my $rect = $win->rect;
 my $ar = $rect->width / $rect->height;
diff --git a/testcases/t/135-floating-focus.t b/testcases/t/135-floating-focus.t
index f5182e1b..4955618f 100644
--- a/testcases/t/135-floating-focus.t
+++ b/testcases/t/135-floating-focus.t
@@ -36,7 +36,7 @@ cmd 'floating enable';
 
 cmd '[id="' . $second->id . '"] focus';
 
-sync_with_i3($x);
+sync_with_i3;
 
 is($x->input_focus, $second->id, 'second con focused');
 
@@ -67,7 +67,7 @@ cmd 'floating enable';
 
 cmd '[id="' . $second->id . '"] focus';
 
-sync_with_i3($x);
+sync_with_i3;
 
 is($x->input_focus, $second->id, 'second con focused');
 
@@ -103,13 +103,13 @@ cmd 'floating enable';
 
 cmd '[id="' . $second->id . '"] focus';
 
-sync_with_i3($x);
+sync_with_i3;
 
 is($x->input_focus, $second->id, 'second con focused');
 
 cmd 'floating enable';
 
-sync_with_i3($x);
+sync_with_i3;
 
 # now kill the second one. focus should fall back to the third one, which is
 # also floating
@@ -132,7 +132,7 @@ $tmp = fresh_workspace;
 $first = open_window({ background_color => '#ff0000' });    # window 8
 $second = open_window({ background_color => '#00ff00' });   # window 9
 
-sync_with_i3($x);
+sync_with_i3;
 
 is($x->input_focus, $second->id, 'second container focused');
 
@@ -142,31 +142,31 @@ is($x->input_focus, $second->id, 'second container focused');
 
 cmd 'focus tiling';
 
-sync_with_i3($x);
+sync_with_i3;
 
 is($x->input_focus, $first->id, 'first (tiling) container focused');
 
 cmd 'focus floating';
 
-sync_with_i3($x);
+sync_with_i3;
 
 is($x->input_focus, $second->id, 'second (floating) container focused');
 
 cmd 'focus floating';
 
-sync_with_i3($x);
+sync_with_i3;
 
 is($x->input_focus, $second->id, 'second (floating) container still focused');
 
 cmd 'focus mode_toggle';
 
-sync_with_i3($x);
+sync_with_i3;
 
 is($x->input_focus, $first->id, 'first (tiling) container focused');
 
 cmd 'focus mode_toggle';
 
-sync_with_i3($x);
+sync_with_i3;
 
 is($x->input_focus, $second->id, 'second (floating) container focused');
 
@@ -180,37 +180,37 @@ $first = open_floating_window({ background_color => '#ff0000' });# window 10
 $second = open_floating_window({ background_color => '#00ff00' }); # window 11
 $third = open_floating_window({ background_color => '#0000ff' }); # window 12
 
-sync_with_i3($x);
+sync_with_i3;
 
 is($x->input_focus, $third->id, 'third container focused');
 
 cmd 'focus left';
 
-sync_with_i3($x);
+sync_with_i3;
 
 is($x->input_focus, $second->id, 'second container focused');
 
 cmd 'focus left';
 
-sync_with_i3($x);
+sync_with_i3;
 
 is($x->input_focus, $first->id, 'first container focused');
 
 cmd 'focus left';
 
-sync_with_i3($x);
+sync_with_i3;
 
 is($x->input_focus, $third->id, 'focus wrapped to third container');
 
 cmd 'focus right';
 
-sync_with_i3($x);
+sync_with_i3;
 
 is($x->input_focus, $first->id, 'focus wrapped to first container');
 
 cmd 'focus right';
 
-sync_with_i3($x);
+sync_with_i3;
 
 is($x->input_focus, $second->id, 'focus on second container');
 
diff --git a/testcases/t/137-floating-unmap.t b/testcases/t/137-floating-unmap.t
index 0d126fea..e91870bc 100644
--- a/testcases/t/137-floating-unmap.t
+++ b/testcases/t/137-floating-unmap.t
@@ -21,7 +21,7 @@ ok($window->mapped, 'Window is mapped');
 
 my $otmp = fresh_workspace;
 
-sync_with_i3($x);
+sync_with_i3;
 
 ok(!$window->mapped, 'Window is not mapped after switching ws');
 
diff --git a/testcases/t/140-focus-lost.t b/testcases/t/140-focus-lost.t
index 042afcfe..e7388fd9 100644
--- a/testcases/t/140-focus-lost.t
+++ b/testcases/t/140-focus-lost.t
@@ -22,7 +22,7 @@ my $left = open_window;
 my $mid = open_window;
 my $right = open_window;
 
-sync_with_i3($x);
+sync_with_i3;
 
 diag("left = " . $left->id . ", mid = " . $mid->id . ", right = " . $right->id);
 
diff --git a/testcases/t/141-resize.t b/testcases/t/141-resize.t
index b2c7d0f3..3f332ce1 100644
--- a/testcases/t/141-resize.t
+++ b/testcases/t/141-resize.t
@@ -10,7 +10,7 @@ cmd 'split v';
 my $top = open_window;
 my $bottom = open_window;
 
-sync_with_i3($x);
+sync_with_i3;
 
 diag("top = " . $top->id . ", bottom = " . $bottom->id);
 
diff --git a/testcases/t/153-floating-originalsize.t b/testcases/t/153-floating-originalsize.t
index dcd1144e..83f3e85d 100644
--- a/testcases/t/153-floating-originalsize.t
+++ b/testcases/t/153-floating-originalsize.t
@@ -17,7 +17,7 @@ cmp_ok($absolute->{width}, '>', 400, 'i3 raised the width');
 cmp_ok($absolute->{height}, '>', 150, 'i3 raised the height');
 
 cmd 'floating toggle';
-sync_with_i3($x);
+sync_with_i3;
 
 ($absolute, $top) = $window->rect;
 
diff --git a/testcases/t/156-fullscreen-focus.t b/testcases/t/156-fullscreen-focus.t
index 78323990..75133cae 100644
--- a/testcases/t/156-fullscreen-focus.t
+++ b/testcases/t/156-fullscreen-focus.t
@@ -46,7 +46,7 @@ my $third = open_window({
 
 $third->map;
 
-sync_with_i3 $x;
+sync_with_i3;
 
 diag("third = " . $third->id);
 
@@ -58,7 +58,7 @@ cmd "move workspace $tmp2";
 
 # verify that the third window has the focus
 
-sync_with_i3($x);
+sync_with_i3;
 
 is($x->input_focus, $third->id, 'third window focused');
 
diff --git a/testcases/t/162-regress-dock-urgent.t b/testcases/t/162-regress-dock-urgent.t
index 39e4eac4..7a0ac487 100644
--- a/testcases/t/162-regress-dock-urgent.t
+++ b/testcases/t/162-regress-dock-urgent.t
@@ -47,7 +47,7 @@ is($docknode->{rect}->{height}, 30, 'dock node has unchanged height');
 
 $window->add_hint('urgency');
 
-sync_with_i3($x);
+sync_with_i3;
 
 does_i3_live;
 
diff --git a/testcases/t/163-wm-state.t b/testcases/t/163-wm-state.t
index 468499d5..b14dd5b5 100644
--- a/testcases/t/163-wm-state.t
+++ b/testcases/t/163-wm-state.t
@@ -9,7 +9,7 @@ use X11::XCB qw(ICCCM_WM_STATE_NORMAL ICCCM_WM_STATE_WITHDRAWN);
 
 my $window = open_window;
 
-sync_with_i3($x);
+sync_with_i3;
 
 is($window->state, ICCCM_WM_STATE_NORMAL, 'WM_STATE normal');
 
diff --git a/testcases/t/164-kill-win-vs-client.t b/testcases/t/164-kill-win-vs-client.t
index 20dd50ca..5c112341 100644
--- a/testcases/t/164-kill-win-vs-client.t
+++ b/testcases/t/164-kill-win-vs-client.t
@@ -14,7 +14,7 @@ sub two_windows {
     my $first = open_window;
     my $second = open_window;
 
-    sync_with_i3 $x;
+    sync_with_i3;
 
     is($x->input_focus, $second->id, 'second window focused');
     ok(@{get_ws_content($tmp)} == 2, 'two containers opened');
diff --git a/testcases/t/165-for_window.t b/testcases/t/165-for_window.t
index 281f840f..c7601809 100644
--- a/testcases/t/165-for_window.t
+++ b/testcases/t/165-for_window.t
@@ -124,13 +124,13 @@ cmp_ok(@content, '==', 1, 'one node on this workspace now');
 is($content[0]->{border}, 'normal', 'normal border');
 
 $window->name('special borderless title');
-sync_with_i3 $x;
+sync_with_i3;
 
 @content = @{get_ws_content($tmp)};
 is($content[0]->{border}, 'none', 'no border');
 
 $window->name('special title');
-sync_with_i3 $x;
+sync_with_i3;
 
 cmd 'border normal';
 
@@ -138,7 +138,7 @@ cmd 'border normal';
 is($content[0]->{border}, 'normal', 'border reset to normal');
 
 $window->name('special borderless title');
-sync_with_i3 $x;
+sync_with_i3;
 
 @content = @{get_ws_content($tmp)};
 is($content[0]->{border}, 'normal', 'still normal border');
@@ -235,7 +235,7 @@ wait_for_unmap $window;
 $window->destroy;
 
 # give i3 a chance to delete the window from its tree
-sync_with_i3 $x;
+sync_with_i3;
 
 @content = @{get_ws_content($tmp)};
 cmp_ok(@content, '==', 0, 'no nodes on this workspace now');
@@ -457,7 +457,7 @@ $x->change_property(
 
 $x->flush;
 
-sync_with_i3 $x;
+sync_with_i3;
 
 @content = @{get_ws_content($tmp)};
 cmp_ok(@content, '==', 1, 'one node on this workspace now');
diff --git a/testcases/t/166-assign.t b/testcases/t/166-assign.t
index f42962f3..a10516a6 100644
--- a/testcases/t/166-assign.t
+++ b/testcases/t/166-assign.t
@@ -135,7 +135,7 @@ $window->map;
 # We use sync_with_i3 instead of wait_for_map here because i3 will not actually
 # map the window -- it will be assigned to a different workspace and will only
 # be mapped once you switch to that workspace
-sync_with_i3 $x;
+sync_with_i3;
 
 ok(@{get_ws_content($tmp)} == 0, 'still no containers');
 ok(@{get_ws_content('targetws')} == 2, 'two containers on targetws');
diff --git a/testcases/t/167-workspace_layout.t b/testcases/t/167-workspace_layout.t
index d5a02ca6..e6704d24 100644
--- a/testcases/t/167-workspace_layout.t
+++ b/testcases/t/167-workspace_layout.t
@@ -26,7 +26,7 @@ ok(@{get_ws_content($tmp)} == 0, 'no containers yet');
 my $first = open_window;
 my $second = open_window;
 
-sync_with_i3($x);
+sync_with_i3;
 
 is($x->input_focus, $second->id, 'second window focused');
 my @content = @{get_ws_content($tmp)};
@@ -56,7 +56,7 @@ ok(@{get_ws_content($tmp)} == 0, 'no containers yet');
 $first = open_window;
 $second = open_window;
 
-sync_with_i3($x);
+sync_with_i3;
 
 is($x->input_focus, $second->id, 'second window focused');
 @content = @{get_ws_content($tmp)};
diff --git a/testcases/t/170-force_focus_wrapping.t b/testcases/t/170-force_focus_wrapping.t
index bf66c44e..69d14688 100644
--- a/testcases/t/170-force_focus_wrapping.t
+++ b/testcases/t/170-force_focus_wrapping.t
@@ -70,7 +70,7 @@ cmd 'focus parent';
 
 $third = open_window;
 
-sync_with_i3($x);
+sync_with_i3;
 
 is($x->input_focus, $third->id, 'third window focused');
 
diff --git a/testcases/t/175-startup-notification.t b/testcases/t/175-startup-notification.t
index a794f70a..3a4dbc81 100644
--- a/testcases/t/175-startup-notification.t
+++ b/testcases/t/175-startup-notification.t
@@ -103,7 +103,7 @@ $win->map;
 # We don’t use wait_for_map because the window will not get mapped -- it is on
 # a different workspace.
 # We sync with i3 here to make sure $x->input_focus is updated.
-sync_with_i3($x);
+sync_with_i3;
 
 is(@{get_ws_content($second_ws)}, 0, 'still no containers on the second workspace');
 is(@{get_ws_content($first_ws)}, 1, 'one container on the first workspace');
@@ -117,7 +117,7 @@ mark_window($leader->id);
 
 $win = open_window({ dont_map => 1, client_leader => $leader });
 $win->map;
-sync_with_i3($x);
+sync_with_i3;
 
 is(@{get_ws_content($second_ws)}, 0, 'still no containers on the second workspace');
 is(@{get_ws_content($first_ws)}, 2, 'two containers on the first workspace');
@@ -128,7 +128,7 @@ is(@{get_ws_content($first_ws)}, 2, 'two containers on the first workspace');
 ######################################################################
 
 complete_startup();
-sync_with_i3($x);
+sync_with_i3;
 
 my $otherwin = open_window;
 is(@{get_ws_content($second_ws)}, 1, 'one container on the second workspace');