Added helper function file and updated composer.json accordingly.

app/Http/helpers.php

@@ -0,0 +1,21 @@
+<?php
+
+/*
+ * Returns true with a given percentage.
+ *
+ * @param  int     $prob Probability for true in percent.
+ * 
+ * @return boolean
+ */
+function rand_bool($prob = 50) {
+    if ($prob < 0 or $prob > 100) {
+        throw new InvalidArgumentException('The value for the probability '.
+          ' must be in a range from 0 to 100.');
+    } else if (!is_int($prob)) {
+        throw new InvalidArgumentException('rand_bool only accepts integers.');
+    }
+
+    $rand = rand(1, 100);
+
+    return $rand <= $prob;
+}

composer.json

@@ -19,6 +19,9 @@
         "phpunit/phpunit": "^7.0"
     },
     "autoload": {
+        "files": [
+            "app/Http/helpers.php"
+        ],
         "classmap": [
             "database/seeds",
             "database/factories"