diff --git a/testcases/lib/i3test.pm b/testcases/lib/i3test.pm
index aff23009..52deebc4 100644
--- a/testcases/lib/i3test.pm
+++ b/testcases/lib/i3test.pm
@@ -116,6 +116,7 @@ use Test::More $test_more_args;
 use Data::Dumper;
 use AnyEvent::I3;
 use Time::HiRes qw(sleep);
+use i3test::Test;
 __
     $tester->BAIL_OUT("$@") if $@;
     feature->import(":5.10");
diff --git a/testcases/lib/i3test/Test.pm b/testcases/lib/i3test/Test.pm
new file mode 100644
index 00000000..d83de55b
--- /dev/null
+++ b/testcases/lib/i3test/Test.pm
@@ -0,0 +1,63 @@
+package i3test::Test;
+
+use base 'Test::Builder::Module';
+
+our @EXPORT = qw(is_num_children);
+
+my $CLASS = __PACKAGE__;
+
+=head1 NAME
+
+i3test::Test - Additional test instructions for use in i3 testcases
+
+=head1 SYNOPSIS
+
+  use i3test;
+
+  my $ws = fresh_workspace;
+  is_num_children($ws, 0, 'no containers on this workspace yet');
+  cmd 'open';
+  is_num_children($ws, 1, 'one container after "open"');
+
+  done_testing;
+
+=head1 DESCRIPTION
+
+This module provides convenience methods for i3 testcases. If you notice that a
+certain pattern is present in 5 or more test cases, it should most likely be
+moved into this module.
+
+=head1 EXPORT
+
+=head2 is_num_children($workspace, $expected, $test_name)
+
+Gets the number of children on the given workspace and verifies that they match
+the expected amount of children.
+
+  is_num_children('1', 0, 'no containers on workspace 1 at startup');
+
+=cut
+
+sub is_num_children {
+    my ($workspace, $num_children, $name) = @_;
+    my $tb = $CLASS->builder;
+
+    my $con = i3test::get_ws($workspace);
+    $tb->ok(defined($con), "Workspace $workspace exists");
+    if (!defined($con)) {
+        $tb->skip("Workspace does not exist, skipping is_num_children");
+        return;
+    }
+
+    my $got_num_children = scalar @{$con->{nodes}};
+
+    $tb->is_num($got_num_children, $num_children, $name);
+}
+
+=head1 AUTHOR
+
+Michael Stapelberg <michael@i3wm.org>
+
+=cut
+
+1
diff --git a/testcases/t/119-match.t b/testcases/t/119-match.t
index e6a4e832..b02cc1e0 100644
--- a/testcases/t/119-match.t
+++ b/testcases/t/119-match.t
@@ -26,8 +26,7 @@ my $win = $content->[0];
 cmd q|[class=".*"] kill|;
 cmd q|[con_id="99999"] kill|;
 
-$content = get_ws_content($tmp);
-ok(@{$content} == 1, 'window still there');
+is_num_children($tmp, 1, 'window still there');
 
 # now kill the window
 cmd 'nop now killing the window';
@@ -37,8 +36,7 @@ cmd qq|[con_id="$id"] kill|;
 wait_for_unmap $window;
 
 cmd 'nop checking if its gone';
-$content = get_ws_content($tmp);
-ok(@{$content} == 0, 'window killed');
+is_num_children($tmp, 0, 'window killed');
 
 # TODO: same test, but with pcre expressions
 
@@ -86,15 +84,13 @@ my $right = open_special(name => 'right');
 ok($right->mapped, 'right window mapped');
 
 # two windows should be here
-$content = get_ws_content($tmp);
-ok(@{$content} == 2, 'two windows opened');
+is_num_children($tmp, 2, 'two windows opened');
 
 cmd '[class="special" title="left"] kill';
 
 sync_with_i3;
 
-$content = get_ws_content($tmp);
-is(@{$content}, 1, 'one window still there');
+is_num_children($tmp, 1, 'one window still there');
 
 ######################################################################
 # check that regular expressions work
@@ -104,17 +100,11 @@ $tmp = fresh_workspace;
 
 $left = open_special(name => 'left', wm_class => 'special7');
 ok($left->mapped, 'left window mapped');
-
-# two windows should be here
-$content = get_ws_content($tmp);
-ok(@{$content} == 1, 'window opened');
+is_num_children($tmp, 1, 'window opened');
 
 cmd '[class="^special[0-9]$"] kill';
-
 wait_for_unmap $left;
-
-$content = get_ws_content($tmp);
-is(@{$content}, 0, 'window killed');
+is_num_children($tmp, 0, 'window killed');
 
 ######################################################################
 # check that UTF-8 works when matching
@@ -124,16 +114,10 @@ $tmp = fresh_workspace;
 
 $left = open_special(name => 'ä 3', wm_class => 'special7');
 ok($left->mapped, 'left window mapped');
-
-# two windows should be here
-$content = get_ws_content($tmp);
-ok(@{$content} == 1, 'window opened');
+is_num_children($tmp, 1, 'window opened');
 
 cmd '[title="^\w [3]$"] kill';
-
 wait_for_unmap $left;
-
-$content = get_ws_content($tmp);
-is(@{$content}, 0, 'window killed');
+is_num_children($tmp, 0, 'window killed');
 
 done_testing;
diff --git a/testcases/t/124-move.t b/testcases/t/124-move.t
index 052cdbff..c093e47b 100644
--- a/testcases/t/124-move.t
+++ b/testcases/t/124-move.t
@@ -100,14 +100,12 @@ is($nodes->[1]->{id}, $second, 'second container on bottom');
 
 # move it outside again
 cmd 'move left';
-$content = get_ws_content($tmp);
-is(@{$content}, 3, 'three nodes on this workspace');
+is_num_children($tmp, 3, 'three containers after moving left');
 
 # due to automatic flattening/cleanup, the remaining split container
 # will be replaced by the con itself, so we will still have 3 nodes
 cmd 'move right';
-$content = get_ws_content($tmp);
-is(@{$content}, 2, 'two nodes on this workspace');
+is_num_children($tmp, 2, 'two containers after moving right (flattening)');
 
 ######################################################################
 # 4) We create two v-split containers on the workspace, then we move
@@ -128,8 +126,7 @@ cmd "move right";
 cmd 'focus left';
 cmd "move right";
 
-$content = get_ws_content($otmp);
-is(@{$content}, 1, 'only one nodes on this workspace');
+is_num_children($otmp, 1, 'only one node on this workspace');
 
 ######################################################################
 # 5) test moving floating containers.
diff --git a/testcases/t/132-move-workspace.t b/testcases/t/132-move-workspace.t
index 0f1cbcc1..c56a17a4 100644
--- a/testcases/t/132-move-workspace.t
+++ b/testcases/t/132-move-workspace.t
@@ -18,20 +18,20 @@ sub move_workspace_test {
     my $tmp2 = get_unused_workspace();
     cmd "workspace $tmp";
 
-    ok(@{get_ws_content($tmp)} == 0, 'no containers yet');
+    is_num_children($tmp, 0, 'no containers yet');
 
     my $first = open_empty_con($i3);
     my $second = open_empty_con($i3);
-    ok(@{get_ws_content($tmp)} == 2, 'two containers on first ws');
+    is_num_children($tmp, 2, 'two containers on first ws');
 
     cmd "workspace $tmp2";
-    ok(@{get_ws_content($tmp2)} == 0, 'no containers on second ws yet');
+    is_num_children($tmp2, 0, 'no containers on second ws yet');
 
     cmd "workspace $tmp";
 
     cmd "$movecmd $tmp2";
-    ok(@{get_ws_content($tmp)} == 1, 'one container on first ws anymore');
-    ok(@{get_ws_content($tmp2)} == 1, 'one container on second ws');
+    is_num_children($tmp, 1, 'one container on first ws anymore');
+    is_num_children($tmp2, 1, 'one container on second ws');
     my ($nodes, $focus) = get_ws_content($tmp2);
 
     is($focus->[0], $second, 'same container on different ws');
@@ -53,7 +53,7 @@ move_workspace_test('move container to workspace');
 
 cmd 'workspace 13: meh';
 cmd 'open';
-ok(@{get_ws_content('13: meh')} == 1, 'one container on 13: meh');
+is_num_children('13: meh', 1, 'one container on 13: meh');
 
 ok(!workspace_exists('13'), 'workspace 13 does not exist yet');
 
@@ -61,8 +61,8 @@ cmd 'workspace 12';
 cmd 'open';
 
 cmd 'move to workspace number 13';
-ok(@{get_ws_content('13: meh')} == 2, 'two containers on 13: meh');
-ok(@{get_ws_content('12')} == 0, 'no container on 12 anymore');
+is_num_children('13: meh', 2, 'one container on 13: meh');
+is_num_children('12', 0, 'no container on 12 anymore');
 
 ok(!workspace_exists('13'), 'workspace 13 does still not exist');
 
@@ -76,28 +76,28 @@ ok(!workspace_exists('13'), 'workspace 13 does still not exist');
 my $tmp = get_unused_workspace();
 my $tmp2 = get_unused_workspace();
 cmd "workspace $tmp";
-ok(@{get_ws_content($tmp)} == 0, 'no containers yet');
+is_num_children($tmp, 0, 'no containers yet');
 my $first = open_empty_con($i3);
 my $second = open_empty_con($i3);
-ok(@{get_ws_content($tmp)} == 2, 'two containers on first ws');
+is_num_children($tmp, 2, 'two containers');
 
 cmd "workspace $tmp2";
-ok(@{get_ws_content($tmp2)} == 0, 'no containers yet');
+is_num_children($tmp2, 0, 'no containers yet');
 my $third = open_empty_con($i3);
-ok(@{get_ws_content($tmp2)} == 1, 'one container on second ws');
+is_num_children($tmp2, 1, 'one container on second ws');
 
 # go back to the first workspace, move one of the containers to the next one
 cmd "workspace $tmp";
 cmd 'move workspace next';
-ok(@{get_ws_content($tmp)} == 1, 'one container on first ws');
-ok(@{get_ws_content($tmp2)} == 2, 'two containers on second ws');
+is_num_children($tmp, 1, 'one container on first ws');
+is_num_children($tmp2, 2, 'two containers on second ws');
 
 # go to the second workspace and move two containers to the first one
 cmd "workspace $tmp2";
 cmd 'move workspace prev';
 cmd 'move workspace prev';
-ok(@{get_ws_content($tmp)} == 3, 'three containers on first ws');
-ok(@{get_ws_content($tmp2)} == 0, 'no containers on second ws');
+is_num_children($tmp, 3, 'three containers on first ws');
+is_num_children($tmp2, 0, 'no containers on second ws');
 
 ###################################################################
 # check if 'move workspace current' works
@@ -108,16 +108,16 @@ $tmp2 = get_unused_workspace();
 
 cmd "workspace $tmp";
 $first = open_window(name => 'win-name');
-ok(@{get_ws_content($tmp)} == 1, 'one container on first ws');
+is_num_children($tmp, 1, 'one container on first ws');
 
 cmd "workspace $tmp2";
-ok(@{get_ws_content($tmp2)} == 0, 'no containers yet');
+is_num_children($tmp2, 0, 'no containers yet');
 
 cmd qq|[title="win-name"] move workspace $tmp2|;
-ok(@{get_ws_content($tmp2)} == 1, 'one container on second ws');
+is_num_children($tmp2, 1, 'one container on second ws');
 
 cmd qq|[title="win-name"] move workspace $tmp|;
-ok(@{get_ws_content($tmp2)} == 0, 'no containers on second ws');
+is_num_children($tmp2, 0, 'no containers on second ws');
 
 ###################################################################
 # check if floating cons are moved to new workspaces properly
@@ -150,12 +150,12 @@ cmd 'open';
 
 cmd 'workspace 16';
 cmd 'open';
-is(@{get_ws('16')->{nodes}}, 1, 'one node on ws 16');
+is_num_children('16', 1, 'one node on ws 16');
 
 cmd "workspace $tmp";
 cmd 'open';
 cmd 'move workspace number 16';
-is(@{get_ws('16')->{nodes}}, 2, 'two nodes on ws 16');
+is_num_children('16', 2, 'two nodes on ws 16');
 
 ok(!workspace_exists('17'), 'workspace 17 does not exist yet');
 cmd 'open';
diff --git a/testcases/t/175-startup-notification.t b/testcases/t/175-startup-notification.t
index 3a4dbc81..2c6ce353 100644
--- a/testcases/t/175-startup-notification.t
+++ b/testcases/t/175-startup-notification.t
@@ -58,7 +58,7 @@ END_OF_C_CODE
 
 my $first_ws = fresh_workspace;
 
-is(@{get_ws_content($first_ws)}, 0, 'no containers on this workspace yet');
+is_num_children($first_ws, 0, 'no containers on this workspace yet');
 
 ######################################################################
 # 1) initiate startup, switch workspace, create window
@@ -95,7 +95,7 @@ is(get_startup_id(), $startup_id, 'libstartup-notification returns the same id')
 
 my $second_ws = fresh_workspace;
 
-is(@{get_ws_content($second_ws)}, 0, 'no containers on the second workspace yet');
+is_num_children($second_ws, 0, 'no containers on the second workspace yet');
 
 my $win = open_window({ dont_map => 1 });
 mark_window($win->id);
@@ -105,8 +105,8 @@ $win->map;
 # We sync with i3 here to make sure $x->input_focus is updated.
 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');
+is_num_children($second_ws, 0, 'still no containers on the second workspace');
+is_num_children($first_ws, 1, 'one container on the first workspace');
 
 ######################################################################
 # same thing, but with _NET_STARTUP_ID set on the leader
@@ -119,8 +119,8 @@ $win = open_window({ dont_map => 1, client_leader => $leader });
 $win->map;
 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');
+is_num_children($second_ws, 0, 'still no containers on the second workspace');
+is_num_children($first_ws, 2, 'two containers on the first workspace');
 
 ######################################################################
 # 2) open another window after the startup process is completed
@@ -131,7 +131,7 @@ complete_startup();
 sync_with_i3;
 
 my $otherwin = open_window;
-is(@{get_ws_content($second_ws)}, 1, 'one container on the second workspace');
+is_num_children($second_ws, 1, 'one container on the second workspace');
 
 ######################################################################
 # 3) test that the --no-startup-id flag for exec leads to no DESKTOP_STARTUP_ID
@@ -166,5 +166,4 @@ unlink($tmp);
 
 is($startup_id, '', 'startup_id empty');
 
-
 done_testing;
diff --git a/testcases/t/179-regress-multiple-ws.t b/testcases/t/179-regress-multiple-ws.t
index 21271170..be3cc687 100644
--- a/testcases/t/179-regress-multiple-ws.t
+++ b/testcases/t/179-regress-multiple-ws.t
@@ -15,11 +15,11 @@ my $keep_open_con = open_empty_con($i3);
 my $tmp = fresh_workspace;
 my $con = open_empty_con($i3);
 
-is(@{get_ws_content($tmp)}, 1, 'one container');
-is(@{get_ws_content($old)}, 1, 'one container on old ws');
+is_num_children($tmp, 1, 'one container');
+is_num_children($old, 1, 'one container on old ws');
 
 cmd 'move workspace prev; workspace prev';
 
-is(@{get_ws_content($old)}, 2, 'container moved away');
+is_num_children($old, 2, 'container moved away');
 
 done_testing;
diff --git a/testcases/t/186-regress-assign-focus-parent.t b/testcases/t/186-regress-assign-focus-parent.t
index 6f2e584f..4f4db430 100644
--- a/testcases/t/186-regress-assign-focus-parent.t
+++ b/testcases/t/186-regress-assign-focus-parent.t
@@ -22,29 +22,21 @@ my $i3 = i3(get_socket_path(0));
 cmd 'workspace targetws';
 
 open_window(name => "testcase");
-
-my $nodes = get_ws_content('targetws');
-is(scalar @$nodes, 1, 'precisely one window');
+is_num_children('targetws', 1, 'precisely one window');
 
 open_window(name => "testcase");
-
-$nodes = get_ws_content('targetws');
-is(scalar @$nodes, 2, 'precisely two windows');
+is_num_children('targetws', 2, 'precisely two windows');
 
 cmd 'split v';
 
 open_window(name => "testcase");
-
-$nodes = get_ws_content('targetws');
-is(scalar @$nodes, 2, 'still two windows');
+is_num_children('targetws', 2, 'still two windows');
 
 # focus parent. the new window should now be opened right next to the last one.
 cmd 'focus parent';
 
 open_window(name => "testcase");
-
-$nodes = get_ws_content('targetws');
-is(scalar @$nodes, 3, 'new window opened next to last one');
+is_num_children('targetws', 3, 'new window opened next to last one');
 
 exit_gracefully($pid);
 
diff --git a/testcases/t/190-scratchpad-diff-ws.t b/testcases/t/190-scratchpad-diff-ws.t
index 9b6e6c7a..ed03f210 100644
--- a/testcases/t/190-scratchpad-diff-ws.t
+++ b/testcases/t/190-scratchpad-diff-ws.t
@@ -45,8 +45,7 @@ my $win = open_window;
 my $scratch = open_special;
 cmd '[class="special"] move scratchpad';
 
-my ($nodes, $focus) = get_ws_content($tmp);
-is(scalar @$nodes, 1, 'one window on current ws');
+is_num_children($tmp, 1, 'one window on current ws');
 
 my $otmp = fresh_workspace;
 cmd 'scratchpad show';
diff --git a/testcases/t/501-scratchpad.t b/testcases/t/501-scratchpad.t
index 97a64a4a..9305239a 100644
--- a/testcases/t/501-scratchpad.t
+++ b/testcases/t/501-scratchpad.t
@@ -25,18 +25,18 @@ my $i3 = i3(get_socket_path());
 sub verify_scratchpad_on_same_ws {
     my ($ws) = @_;
 
-    is(scalar @{get_ws($ws)->{nodes}}, 0, 'no nodes on this ws');
+    is_num_children($ws, 0, 'no nodes on this ws');
 
     my $window = open_window;
 
-    is(scalar @{get_ws($ws)->{nodes}}, 1, 'one nodes on this ws');
+    is_num_children($ws, 1, 'one nodes on this ws');
 
     cmd 'move scratchpad';
 
-    is(scalar @{get_ws($ws)->{nodes}}, 0, 'no nodes on this ws');
+    is_num_children($ws, 0, 'no nodes on this ws');
 
     cmd 'scratchpad show';
-    is(scalar @{get_ws($ws)->{nodes}}, 0, 'no nodes on this ws');
+    is_num_children($ws, 0, 'no nodes on this ws');
     is(scalar @{get_ws($ws)->{floating_nodes}}, 1, 'one floating node on this ws');
 }
 
@@ -61,21 +61,21 @@ sub verify_scratchpad_switch {
 
     cmd "workspace $first";
 
-    is(scalar @{get_ws($first)->{nodes}}, 0, 'no nodes on this ws');
+    is_num_children($first, 0, 'no nodes on this ws');
 
     my $window = open_window;
 
-    is(scalar @{get_ws($first)->{nodes}}, 1, 'one nodes on this ws');
+    is_num_children($first, 1, 'one nodes on this ws');
 
     cmd 'move scratchpad';
 
-    is(scalar @{get_ws($first)->{nodes}}, 0, 'no nodes on this ws');
+    is_num_children($first, 0, 'no nodes on this ws');
 
     cmd "workspace $second";
 
     cmd 'scratchpad show';
     my $ws = get_ws($second);
-    is(scalar @{$ws->{nodes}}, 0, 'no nodes on this ws');
+    is_num_children($second, 0, 'no nodes on this ws');
     is(scalar @{$ws->{floating_nodes}}, 1, 'one floating node on this ws');
 
     # Verify that the coordinates are within bounds.
diff --git a/testcases/t/505-scratchpad-resolution.t b/testcases/t/505-scratchpad-resolution.t
index 3d0bcfa6..ce85cfc0 100644
--- a/testcases/t/505-scratchpad-resolution.t
+++ b/testcases/t/505-scratchpad-resolution.t
@@ -22,15 +22,13 @@ sync_with_i3;
 sub verify_scratchpad_doesnt_move {
     my ($ws) = @_;
 
-    is(scalar @{get_ws($ws)->{nodes}}, 0, 'no nodes on this ws');
+    is_num_children($ws, 0, 'no nodes on this ws');
 
     my $window = open_window;
-
-    is(scalar @{get_ws($ws)->{nodes}}, 1, 'one nodes on this ws');
+    is_num_children($ws, 1, 'one node on this ws');
 
     cmd 'move scratchpad';
-
-    is(scalar @{get_ws($ws)->{nodes}}, 0, 'no nodes on this ws');
+    is_num_children($ws, 0, 'no nodes on this ws');
 
     my $last_x = -1;
     for (1 .. 20) {