diff --git a/src/Model/LogEntry.php b/src/Model/LogEntry.php
index c598589..15dc06e 100644
--- a/src/Model/LogEntry.php
+++ b/src/Model/LogEntry.php
@@ -90,13 +90,13 @@ public function getCMSFields()
     {
         $fields = parent::getCMSFields();
 
-        $data = Convert::json2obj($this->getField('Entry'));
+        $data = json_decode($this->getField('Entry'));
         $fields->addFieldToTab(
             'Root.Main',
             LiteralField::create(
                 'Entry',
                 '<pre class="logviewer-logentry-entry"><code>'
-                . Convert::raw2json($data, JSON_PRETTY_PRINT)
+                . json_encode($data, JSON_PRETTY_PRINT)
                 . '</code></pre>'
             )
         );
diff --git a/tests/Admin/LogViewerAdminTest.php b/tests/Admin/LogViewerAdminTest.php
index 0c6d371..12e1dc2 100644
--- a/tests/Admin/LogViewerAdminTest.php
+++ b/tests/Admin/LogViewerAdminTest.php
@@ -31,7 +31,7 @@ class LogViewerAdminTest extends FunctionalTest
     /**
      * {@inheritDoc}
      */
-    public function setUp()
+    public function setUp(): void
     {
         parent::setUp();
 
diff --git a/tests/Forms/GridField/GridFieldClearAllButtonTest.php b/tests/Forms/GridField/GridFieldClearAllButtonTest.php
index ddf2421..0fb6f52 100644
--- a/tests/Forms/GridField/GridFieldClearAllButtonTest.php
+++ b/tests/Forms/GridField/GridFieldClearAllButtonTest.php
@@ -35,7 +35,7 @@ class GridFieldClearAllButtonTest extends SapphireTest
     /**
      * {@inheritDoc}
      */
-    public function setUp()
+    public function setUp(): void
     {
         parent::setUp();
 
@@ -67,9 +67,9 @@ public function testGetHtmlFragments()
         $fragments = $this->getSubject()->getHTMLFragments($this->gridField);
 
         $this->assertArrayHasKey('before', $fragments);
-        $this->assertContains('Clear all', $fragments['before']);
-        $this->assertContains('clear-all-logs', $fragments['before']);
-        $this->assertContains('font-icon-trash-bin action_clear', $fragments['before']);
+        $this->assertStringContainsString('Clear all', $fragments['before']);
+        $this->assertStringContainsString('clear-all-logs', $fragments['before']);
+        $this->assertStringContainsString('font-icon-trash-bin action_clear', $fragments['before']);
     }
 
     /**
diff --git a/tests/Handler/DataObjectHandlerTest.php b/tests/Handler/DataObjectHandlerTest.php
index d5b4d62..172fd81 100644
--- a/tests/Handler/DataObjectHandlerTest.php
+++ b/tests/Handler/DataObjectHandlerTest.php
@@ -2,6 +2,7 @@
 
 namespace SilverLeague\LogViewer\Tests\Handler;
 
+use Monolog\Logger;
 use Psr\Log\LoggerInterface;
 use SilverLeague\LogViewer\Handler\DataObjectHandler;
 use SilverLeague\LogViewer\Model\LogEntry;
@@ -19,13 +20,13 @@ class DataObjectHandlerTest extends SapphireTest
      * A Logger instance
      * @var Monolog\Logger
      */
-    protected $logger;
+    protected Logger $logger;
 
     /**
      * The original logger handlers
      * @var Monolog\LoggerInterface[]
      */
-    protected $originalHandlers = [];
+    protected  $originalHandlers = [];
 
     /**
      * {@inheritDoc}
@@ -37,7 +38,7 @@ class DataObjectHandlerTest extends SapphireTest
      *
      * {@inheritDoc}
      */
-    public function setUp()
+    public function setUp(): void
     {
         parent::setUp();
 
@@ -54,10 +55,10 @@ public function setUp()
     public function testWriteToDefaultLogger()
     {
         $this->logger->pushHandler(new DataObjectHandler);
-        $this->logger->addError('Hello world');
+        $this->logger->error('Hello world');
 
         $logEntry = LogEntry::get()->first();
-        $this->assertContains('Hello world', $logEntry->Entry);
+        $this->assertStringContainsString('Hello world', $logEntry->Entry);
         $this->assertSame('ERROR', $logEntry->Level);
     }
 
@@ -70,13 +71,13 @@ public function testDontLogMessagesLowerThanMinimumLever()
         LogEntry::get()->removeAll();
         $this->logger->pushHandler(new DataObjectHandler);
 
-        $this->logger->addDebug('Debug');
+        $this->logger->debug('Debug');
         $this->assertSame(0, LogEntry::get()->count());
 
-        $this->logger->addWarning('Warning');
+        $this->logger->warning('Warning');
         $this->assertGreaterThan(0, LogEntry::get()->filter('Level', 'WARNING')->count());
 
-        $this->logger->addAlert('Alert');
+        $this->logger->alert('Alert');
         $this->assertGreaterThan(0, LogEntry::get()->filter('Level', 'ALERT')->count());
     }
 
@@ -85,8 +86,8 @@ public function testDontLogMessagesLowerThanMinimumLever()
      */
     public function testGetMinimumLogLevelFromConfiguration()
     {
-        Config::modify()->set(LogEntry::class, 'minimum_log_level', 123);
-        $this->assertSame(123, (new DataObjectHandler)->getMinimumLogLevel());
+        Config::modify()->set(LogEntry::class, 'minimum_log_level', 300);
+        $this->assertSame(300, (new DataObjectHandler)->getMinimumLogLevel());
     }
 
     /**
@@ -94,7 +95,7 @@ public function testGetMinimumLogLevelFromConfiguration()
      *
      * {@inheritDoc}
      */
-    public function tearDown()
+    public function tearDown(): void
     {
         $this->logger->setHandlers($this->originalHandlers);
 
diff --git a/tests/Model/LogEntryTest.php b/tests/Model/LogEntryTest.php
index a5051c9..4f27a63 100644
--- a/tests/Model/LogEntryTest.php
+++ b/tests/Model/LogEntryTest.php
@@ -85,13 +85,14 @@ public function testLogEntriesAreFormattedAsJson()
         ];
 
         $entry = LogEntry::create();
-        $entry->Entry = Convert::raw2json($data);
+        $entry->Entry = json_encode($data);
+
 
         $fields = $entry->getCMSFields();
         $field = $fields->fieldByName('Root.Main.Entry');
 
         $this->assertInstanceOf(LiteralField::class, $field);
-        $this->assertContains(Convert::raw2json($data, JSON_PRETTY_PRINT), $field->getContent());
-        $this->assertContains('<pre class="logviewer-logentry-entry"><code>', $field->getContent());
+        $this->assertStringContainsString(json_encode($data, JSON_PRETTY_PRINT), $field->getContent());
+        $this->assertStringContainsString('<pre class="logviewer-logentry-entry"><code>', $field->getContent());
     }
 }
diff --git a/tests/Task/RemoveOldLogEntriesTaskTest.php b/tests/Task/RemoveOldLogEntriesTaskTest.php
index fc88385..c303295 100644
--- a/tests/Task/RemoveOldLogEntriesTaskTest.php
+++ b/tests/Task/RemoveOldLogEntriesTaskTest.php
@@ -31,8 +31,8 @@ class RemoveOldLogEntriesTaskTest extends SapphireTest
     public function testClassProperties()
     {
         $task = new RemoveOldLogEntriesTask;
-        $this->assertContains('Remove LogEntry', $task->getTitle());
-        $this->assertContains('that are older than', $task->getDescription());
+        $this->assertStringContainsString('Remove LogEntry', $task->getTitle());
+        $this->assertStringContainsString('that are older than', $task->getDescription());
         $this->assertSame('RemoveOldLogEntriesTask', Config::inst()->get(RemoveOldLogEntriesTask::class, 'segment'));
     }
 
@@ -99,10 +99,10 @@ public function testRemoveOldLogEntries()
         $buffer = ob_get_clean();
 
         $this->assertTrue($result);
-        $this->assertContains('Removed 6 log(s)', $buffer);
+        $this->assertStringContainsString('Removed 6 log(s)', $buffer);
         // Nothing to do the second time
         $this->assertFalse($second);
-        $this->assertContains('Removed 0 log(s)', $buffer);
-        $this->assertContains('older than 1 day(s)', $buffer);
+        $this->assertStringContainsString('Removed 0 log(s)', $buffer);
+        $this->assertStringContainsString('older than 1 day(s)', $buffer);
     }
 }