diff --git a/.travis.yml b/.travis.yml
index 3a6b774..aea45fe 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,8 +1,8 @@
 language: php
 
 php:
-  - 7.1
   - 7.2
+  - 7.3
 
 env:
   matrix:
diff --git a/composer.json b/composer.json
index a16bece..2ac5974 100644
--- a/composer.json
+++ b/composer.json
@@ -22,11 +22,12 @@
         }
     ],
     "require": {
-        "laravel/framework": "~5.5"
+        "laravel/framework": "~5.5|^6.0"
     },
     "require-dev": {
-        "phpunit/phpunit": "^6.2|^7.0",
-        "orchestra/testbench": "~3.5.0|~3.6.0"
+        "phpunit/phpunit": "^6.2|^7.0|^8.0",
+        "orchestra/testbench": "~3.5.0|~3.6.0|~4.0.0",
+        "orchestra/database": "~3.5.0|~3.6.0|~4.0.0"
     },
     "autoload": {
         "psr-4": {
diff --git a/database/factories/UserFactory.php b/database/factories/UserFactory.php
index 790e8eb..43cc188 100644
--- a/database/factories/UserFactory.php
+++ b/database/factories/UserFactory.php
@@ -1,4 +1,7 @@
 <?php
+
+use Illuminate\Support\Str;
+
 /*
 |--------------------------------------------------------------------------
 | Model Factories
@@ -12,9 +15,9 @@
 
 $factory->define(\Rennokki\Schedule\Test\Models\User::class, function () {
     return [
-        'name' => 'Name'.str_random(5),
-        'email' => str_random(5).'@gmail.com',
+        'name' => 'Name'.Str::random(5),
+        'email' => Str::random(5).'@gmail.com',
         'password' => '$2y$10$TKh8H1.PfQx37YgCzwiKb.KjNyWgaHb9cbcoQgdIVFlYg7B77UdFm', // secret
-        'remember_token' => str_random(10),
+        'remember_token' => Str::random(10),
     ];
 });
diff --git a/database/migrations/2018_05_19_135648_schedules.php b/database/migrations/2018_05_19_135648_schedules.php
index 6c849b1..a16b3cb 100644
--- a/database/migrations/2018_05_19_135648_schedules.php
+++ b/database/migrations/2018_05_19_135648_schedules.php
@@ -1,8 +1,8 @@
 <?php
 
-use Illuminate\Support\Facades\Schema;
-use Illuminate\Database\Schema\Blueprint;
 use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
 
 class Schedules extends Migration
 {
diff --git a/src/TimeRange.php b/src/TimeRange.php
index 768fdcb..b67a808 100644
--- a/src/TimeRange.php
+++ b/src/TimeRange.php
@@ -57,7 +57,7 @@ public function isInTimeRange($hourMinute): bool
             return false;
         }
 
-        list($hour, $minute) = explode(':', $hourMinute);
+        [$hour, $minute] = explode(':', $hourMinute);
         $hour = (int) $hour;
         $minute = (int) $minute;
 
diff --git a/src/Traits/HasSchedule.php b/src/Traits/HasSchedule.php
index 564b888..622fa4f 100644
--- a/src/Traits/HasSchedule.php
+++ b/src/Traits/HasSchedule.php
@@ -156,7 +156,7 @@ public function deleteExclusions()
      */
     public function isAvailableOn($dateOrDay): bool
     {
-        if (in_array($dateOrDay, Self::$availableDays)) {
+        if (in_array($dateOrDay, self::$availableDays)) {
             return (bool) (count($this->getSchedule()[$dateOrDay]) > 0);
         }
 
@@ -209,7 +209,7 @@ public function isAvailableOnAt($dateOrDay, $time): bool
     {
         $timeRanges = null;
 
-        if (in_array($dateOrDay, Self::$availableDays)) {
+        if (in_array($dateOrDay, self::$availableDays)) {
             $timeRanges = $this->getSchedule()[$dateOrDay];
         }
 
@@ -267,7 +267,7 @@ public function getHoursOn($dateOrDay): int
         $totalHours = 0;
         $timeRanges = null;
 
-        if (in_array($dateOrDay, Self::$availableDays)) {
+        if (in_array($dateOrDay, self::$availableDays)) {
             $timeRanges = $this->getSchedule()[$dateOrDay];
         }
 
@@ -311,7 +311,7 @@ public function getMinutesOn($dateOrDay): int
         $totalMinutes = 0;
         $timeRanges = null;
 
-        if (in_array($dateOrDay, Self::$availableDays)) {
+        if (in_array($dateOrDay, self::$availableDays)) {
             $timeRanges = $this->getSchedule()[$dateOrDay];
         }
 
@@ -415,12 +415,12 @@ protected function normalizeScheduleArray(array $scheduleArray): array
     {
         $finalScheduleArray = [];
 
-        foreach (Self::$availableDays as $availableDay) {
+        foreach (self::$availableDays as $availableDay) {
             $finalScheduleArray[$availableDay] = [];
         }
 
         foreach ($scheduleArray as $day => $timeArray) {
-            if (! in_array($day, Self::$availableDays)) {
+            if (! in_array($day, self::$availableDays)) {
                 continue;
             }
 
diff --git a/tests/ScheduleTest.php b/tests/ScheduleTest.php
index 5ee8f5f..34f1339 100644
--- a/tests/ScheduleTest.php
+++ b/tests/ScheduleTest.php
@@ -13,7 +13,7 @@ class ScheduleTest extends TestCase
         'saturday', 'sunday',
     ];
 
-    public function setUp()
+    public function setUp(): void
     {
         parent::setUp();
 
diff --git a/tests/TestCase.php b/tests/TestCase.php
index 9abd1fc..bf5f192 100644
--- a/tests/TestCase.php
+++ b/tests/TestCase.php
@@ -2,13 +2,13 @@
 
 namespace Rennokki\Schedule\Test;
 
-use Rennokki\Schedule\Test\Models\User;
-use Rennokki\Schedule\Models\ScheduleModel;
 use Orchestra\Testbench\TestCase as Orchestra;
+use Rennokki\Schedule\Models\ScheduleModel;
+use Rennokki\Schedule\Test\Models\User;
 
 abstract class TestCase extends Orchestra
 {
-    public function setUp()
+    public function setUp(): void
     {
         parent::setUp();