diff --git a/testcases/lib/i3test.pm b/testcases/lib/i3test.pm
index 52deebc4..86886de1 100644
--- a/testcases/lib/i3test.pm
+++ b/testcases/lib/i3test.pm
@@ -33,7 +33,6 @@ our @EXPORT = qw(
     open_floating_window
     get_dock_clients
     cmd
-    cmp_float
     sync_with_i3
     does_i3_live
     exit_gracefully
@@ -566,13 +565,7 @@ sub launch_with_config {
     return $i3_pid;
 }
 
-# compares two floats and return true if they differ less
-# then 1e-6
-sub cmp_float {
-  my ($a, $b) = @_;
 
-  return abs($a - $b) < 1e-6;
-}
 
 package i3test::X11;
 use parent 'X11::XCB::Connection';
diff --git a/testcases/lib/i3test/Test.pm b/testcases/lib/i3test/Test.pm
index d83de55b..4389971b 100644
--- a/testcases/lib/i3test/Test.pm
+++ b/testcases/lib/i3test/Test.pm
@@ -1,8 +1,12 @@
 package i3test::Test;
+# vim:ts=4:sw=4:expandtab
 
 use base 'Test::Builder::Module';
 
-our @EXPORT = qw(is_num_children);
+our @EXPORT = qw(
+    is_num_children
+    cmp_float
+);
 
 my $CLASS = __PACKAGE__;
 
@@ -54,6 +58,31 @@ sub is_num_children {
     $tb->is_num($got_num_children, $num_children, $name);
 }
 
+=head2 cmp_float($a, $b)
+
+Compares floating point numbers C<$a> and C<$b> and returns true if they differ
+less then 1e-6.
+
+  $tmp = fresh_workspace;
+
+  open_window for (1..4);
+
+  cmd 'resize grow width 10 px or 25 ppt';
+
+  ($nodes, $focus) = get_ws_content($tmp);
+  ok(cmp_float($nodes->[0]->{percent}, 0.166666666666667), 'first window got 16%');
+  ok(cmp_float($nodes->[1]->{percent}, 0.166666666666667), 'second window got 16%');
+  ok(cmp_float($nodes->[2]->{percent}, 0.166666666666667), 'third window got 16%');
+  ok(cmp_float($nodes->[3]->{percent}, 0.50), 'fourth window got 50%');
+
+=cut
+sub cmp_float {
+  my ($a, $b, $name) = @_;
+  my $tb = $CLASS->builder;
+
+  $tb->cmp_ok(abs($a - $b), '<', 1e-6, $name);
+}
+
 =head1 AUTHOR
 
 Michael Stapelberg <michael@i3wm.org>
diff --git a/testcases/t/141-resize.t b/testcases/t/141-resize.t
index 20dc68f4..e769ced7 100644
--- a/testcases/t/141-resize.t
+++ b/testcases/t/141-resize.t
@@ -22,8 +22,8 @@ cmd 'resize grow up 10 px or 25 ppt';
 
 my ($nodes, $focus) = get_ws_content($tmp);
 
-ok(cmp_float($nodes->[0]->{percent}, 0.25), 'top window got only 25%');
-ok(cmp_float($nodes->[1]->{percent}, 0.75), 'bottom window got 75%');
+cmp_float($nodes->[0]->{percent}, 0.25, 'top window got only 25%');
+cmp_float($nodes->[1]->{percent}, 0.75, 'bottom window got 75%');
 
 
 ############################################################
@@ -34,8 +34,8 @@ cmd 'split h';
 
 ($nodes, $focus) = get_ws_content($tmp);
 
-ok(cmp_float($nodes->[0]->{percent}, 0.25), 'top window got only 25%');
-ok(cmp_float($nodes->[1]->{percent}, 0.75), 'bottom window got 75%');
+cmp_float($nodes->[0]->{percent}, 0.25, 'top window got only 25%');
+cmp_float($nodes->[1]->{percent}, 0.75, 'bottom window got 75%');
 
 ############################################################
 # checks that resizing within stacked/tabbed cons works
@@ -52,14 +52,14 @@ cmd 'split h';
 cmd 'layout stacked';
 
 ($nodes, $focus) = get_ws_content($tmp);
-ok(cmp_float($nodes->[0]->{percent}, 0.5), 'top window got 50%');
-ok(cmp_float($nodes->[1]->{percent}, 0.5), 'bottom window got 50%');
+cmp_float($nodes->[0]->{percent}, 0.5, 'top window got 50%');
+cmp_float($nodes->[1]->{percent}, 0.5, 'bottom window got 50%');
 
 cmd 'resize grow up 10 px or 25 ppt';
 
 ($nodes, $focus) = get_ws_content($tmp);
-ok(cmp_float($nodes->[0]->{percent}, 0.25), 'top window got 25%');
-ok(cmp_float($nodes->[1]->{percent}, 0.75), 'bottom window got 75%');
+cmp_float($nodes->[0]->{percent}, 0.25, 'top window got 25%');
+cmp_float($nodes->[1]->{percent}, 0.75, 'bottom window got 75%');
 
 ############################################################
 # Checks that resizing in the parent's parent's orientation works.
@@ -79,14 +79,14 @@ $top = open_window;
 $bottom = open_window;
 
 ($nodes, $focus) = get_ws_content($tmp);
-ok(cmp_float($nodes->[0]->{percent}, 0.5), 'left window got 50%');
-ok(cmp_float($nodes->[1]->{percent}, 0.5), 'right window got 50%');
+cmp_float($nodes->[0]->{percent}, 0.5, 'left window got 50%');
+cmp_float($nodes->[1]->{percent}, 0.5, 'right window got 50%');
 
 cmd 'resize grow left 10 px or 25 ppt';
 
 ($nodes, $focus) = get_ws_content($tmp);
-ok(cmp_float($nodes->[0]->{percent}, 0.25), 'left window got 25%');
-ok(cmp_float($nodes->[1]->{percent}, 0.75), 'right window got 75%');
+cmp_float($nodes->[0]->{percent}, 0.25, 'left window got 25%');
+cmp_float($nodes->[1]->{percent}, 0.75, 'right window got 75%');
 
 ################################################################################
 # Check that the resize grow/shrink width/height syntax works.
@@ -101,8 +101,8 @@ $right = open_window;
 cmd 'resize grow width 10 px or 25 ppt';
 
 ($nodes, $focus) = get_ws_content($tmp);
-ok(cmp_float($nodes->[0]->{percent}, 0.25), 'left window got 25%');
-ok(cmp_float($nodes->[1]->{percent}, 0.75), 'right window got 75%');
+cmp_float($nodes->[0]->{percent}, 0.25, 'left window got 25%');
+cmp_float($nodes->[1]->{percent}, 0.75, 'right window got 75%');
 
 # Now test it with four windows
 $tmp = fresh_workspace;
@@ -112,19 +112,19 @@ open_window for (1..4);
 cmd 'resize grow width 10 px or 25 ppt';
 
 ($nodes, $focus) = get_ws_content($tmp);
-ok(cmp_float($nodes->[0]->{percent}, 0.166666666666667), 'first window got 16%');
-ok(cmp_float($nodes->[1]->{percent}, 0.166666666666667), 'second window got 16%');
-ok(cmp_float($nodes->[2]->{percent}, 0.166666666666667), 'third window got 16%');
-ok(cmp_float($nodes->[3]->{percent}, 0.50), 'fourth window got 50%');
+cmp_float($nodes->[0]->{percent}, 0.166666666666667, 'first window got 16%');
+cmp_float($nodes->[1]->{percent}, 0.166666666666667, 'second window got 16%');
+cmp_float($nodes->[2]->{percent}, 0.166666666666667, 'third window got 16%');
+cmp_float($nodes->[3]->{percent}, 0.50, 'fourth window got 50%');
 
 # height should be a no-op in this situation
 cmd 'resize grow height 10 px or 25 ppt';
 
 ($nodes, $focus) = get_ws_content($tmp);
-ok(cmp_float($nodes->[0]->{percent}, 0.166666666666667), 'first window got 16%');
-ok(cmp_float($nodes->[1]->{percent}, 0.166666666666667), 'second window got 16%');
-ok(cmp_float($nodes->[2]->{percent}, 0.166666666666667), 'third window got 16%');
-ok(cmp_float($nodes->[3]->{percent}, 0.50), 'fourth window got 50%');
+cmp_float($nodes->[0]->{percent}, 0.166666666666667, 'first window got 16%');
+cmp_float($nodes->[1]->{percent}, 0.166666666666667, 'second window got 16%');
+cmp_float($nodes->[2]->{percent}, 0.166666666666667, 'third window got 16%');
+cmp_float($nodes->[3]->{percent}, 0.50, 'fourth window got 50%');
 
 
 ############################################################
diff --git a/testcases/t/191-resize-levels.t b/testcases/t/191-resize-levels.t
index 230a4915..9eef6c0c 100644
--- a/testcases/t/191-resize-levels.t
+++ b/testcases/t/191-resize-levels.t
@@ -23,7 +23,7 @@ cmd 'resize grow left 10px or 25ppt';
 
 my ($nodes, $focus) = get_ws_content($tmp);
 
-ok(cmp_float($nodes->[0]->{percent}, 0.25), 'left container got only 25%');
-ok(cmp_float($nodes->[1]->{percent}, 0.75), 'right container got 75%');
+cmp_float($nodes->[0]->{percent}, 0.25, 'left container got only 25%');
+cmp_float($nodes->[1]->{percent}, 0.75, 'right container got 75%');
 
 done_testing;