diff --git a/lib/CleantalkSP/Common/Scanner/HeuristicAnalyser/tests/.phpcs.xml b/lib/CleantalkSP/Common/Scanner/HeuristicAnalyser/tests/.phpcs.xml
new file mode 100644
index 000000000..10ccec065
--- /dev/null
+++ b/lib/CleantalkSP/Common/Scanner/HeuristicAnalyser/tests/.phpcs.xml
@@ -0,0 +1,30 @@
+<?xml version="1.0"?>
+<ruleset name="PHP compatibility">
+	<description>Sniff code to check different PHP compatibility</description>
+
+	<!-- What to scan -->
+	<file>../</file>
+	<exclude-pattern>/vendor/</exclude-pattern>
+	<exclude-pattern>/lib/</exclude-pattern>
+
+	<!-- How to scan -->
+	<!-- Usage instructions: https://github.com/squizlabs/PHP_CodeSniffer/wiki/Usage -->
+	<!-- Annotated ruleset: https://github.com/squizlabs/PHP_CodeSniffer/wiki/Annotated-ruleset.xml -->
+	<arg value="sp"/> <!-- Show sniff and progress -->
+	<arg name="basepath" value="./"/><!-- Strip the file paths down to the relevant bit -->
+	<arg name="colors"/>
+	<arg name="extensions" value="php"/>
+	<!-- Exclude test directories -->
+	<exclude-pattern>tests/*</exclude-pattern>
+	<exclude-pattern>vendor/*</exclude-pattern>
+	<exclude-pattern>fw_files/*</exclude-pattern>
+	<arg name="exclude" value="PSR12.ControlStructures.ControlStructureSpacing"/>
+	<arg value="n"/>
+
+	<!-- Rules: Check PHP version compatibility -->
+	<!-- https://github.com/PHPCompatibility/PHPCompatibility#sniffing-your-code-for-compatibility-with-specific-php-versions -->
+	<config name="testVersion" value="7.4-"/>
+
+	<rule ref="PHPCompatibility"/>
+	<rule ref="PSR12"/>
+</ruleset>
diff --git a/lib/CleantalkSP/Common/Scanner/HeuristicAnalyser/tests/Scanner/HTMLTest.php b/lib/CleantalkSP/Common/Scanner/HeuristicAnalyser/tests/Scanner/HTMLTest.php
new file mode 100644
index 000000000..a31814267
--- /dev/null
+++ b/lib/CleantalkSP/Common/Scanner/HeuristicAnalyser/tests/Scanner/HTMLTest.php
@@ -0,0 +1,29 @@
+<?php
+
+use CleantalkSP\Common\Scanner\HeuristicAnalyser\Modules\HTML;
+use CleantalkSP\Common\Scanner\HeuristicAnalyser\Modules\Tokens;
+use PHPUnit\Framework\TestCase;
+
+class HTMLTest extends TestCase
+{
+    private $html;
+
+    public function setUp()
+    {
+        $file_content = "<?php
+        echo(
+            '<script>alert(1);</script>'
+        );
+        ?>
+        <script>alert(2);</script>
+        ";
+        $tokens = new Tokens($file_content);
+        $this->html = new HTML($tokens);
+    }
+
+    public function testAnalise()
+    {
+        $this->html->analise();
+        $this->assertEquals('T_INLINE_HTML', $this->html->result);
+    }
+}
diff --git a/lib/CleantalkSP/Common/Scanner/HeuristicAnalyser/tests/Scanner/TokensTest.php b/lib/CleantalkSP/Common/Scanner/HeuristicAnalyser/tests/Scanner/TokensTest.php
new file mode 100644
index 000000000..966e84bbe
--- /dev/null
+++ b/lib/CleantalkSP/Common/Scanner/HeuristicAnalyser/tests/Scanner/TokensTest.php
@@ -0,0 +1,26 @@
+<?php
+
+use CleantalkSP\Common\Scanner\HeuristicAnalyser\DataStructures\Token;
+use CleantalkSP\Common\Scanner\HeuristicAnalyser\Modules\Tokens;
+use PHPUnit\Framework\TestCase;
+
+class TokensTest extends TestCase
+{
+    private $tokens;
+
+    public function setUp()
+    {
+        $file_content = "<?php
+            echo('hello');        
+        ";
+        $this->tokens = new Tokens($file_content);
+    }
+
+    public function testGetTokenFromPosition()
+    {
+        $echo_token = $this->tokens->getTokenFromPosition(2);
+        $this->assertInstanceOf(Token::class, $echo_token);
+        $this->assertEquals($echo_token[0], 'T_ECHO');
+        $this->assertEquals($echo_token[1], 'echo');
+    }
+}
diff --git a/lib/CleantalkSP/Common/Scanner/HeuristicAnalyser/tests/bootstrap.php b/lib/CleantalkSP/Common/Scanner/HeuristicAnalyser/tests/bootstrap.php
new file mode 100644
index 000000000..7386fad60
--- /dev/null
+++ b/lib/CleantalkSP/Common/Scanner/HeuristicAnalyser/tests/bootstrap.php
@@ -0,0 +1,22 @@
+<?php
+
+/**
+ * Autoloader for \CleantalkSP\* classes
+ *
+ * @param string $class
+ *
+ * @return void
+ */
+
+spl_autoload_register(function ($class) {
+
+    // Register class auto loader
+    // Custom modules1
+    if ( strpos($class, 'CleantalkSP') !== false ) {
+        $class      = str_replace('CleantalkSP\Common\Scanner\HeuristicAnalyser\\', DIRECTORY_SEPARATOR, $class);
+        $class_file = dirname(__DIR__) . $class . '.php';
+        if ( file_exists($class_file) ) {
+            require_once($class_file);
+        }
+    }
+});
diff --git a/lib/CleantalkSP/Common/Scanner/HeuristicAnalyser/tests/phpunit.xml b/lib/CleantalkSP/Common/Scanner/HeuristicAnalyser/tests/phpunit.xml
new file mode 100644
index 000000000..dbe592172
--- /dev/null
+++ b/lib/CleantalkSP/Common/Scanner/HeuristicAnalyser/tests/phpunit.xml
@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<phpunit
+        bootstrap="bootstrap.php"
+        colors="true"
+        convertErrorsToExceptions="true"
+        convertNoticesToExceptions="true"
+        convertWarningsToExceptions="true"
+        stopOnFailure="true"
+        beStrictAboutOutputDuringTests="true"
+>
+    <testsuites>
+        <testsuite name="CleanTalk SPBCT Heuristic Analyser classes Unit Tests">
+            <directory suffix=".php">./</directory>
+            <exclude>./bootstrap.php</exclude>
+        </testsuite>
+    </testsuites>
+</phpunit>
diff --git a/lib/CleantalkSP/Common/Scanner/SignaturesAnalyser/tests/.phpcs.xml b/lib/CleantalkSP/Common/Scanner/SignaturesAnalyser/tests/.phpcs.xml
new file mode 100644
index 000000000..f21f21787
--- /dev/null
+++ b/lib/CleantalkSP/Common/Scanner/SignaturesAnalyser/tests/.phpcs.xml
@@ -0,0 +1,30 @@
+<?xml version="1.0"?>
+<ruleset name="PHP compatibility">
+	<description>Sniff code to check different PHP compatibility</description>
+
+	<!-- What to scan -->
+	<file>../</file>
+	<exclude-pattern>/vendor/</exclude-pattern>
+	<exclude-pattern>/lib/</exclude-pattern>
+
+	<!-- How to scan -->
+	<!-- Usage instructions: https://github.com/squizlabs/PHP_CodeSniffer/wiki/Usage -->
+	<!-- Annotated ruleset: https://github.com/squizlabs/PHP_CodeSniffer/wiki/Annotated-ruleset.xml -->
+	<arg value="sp"/> <!-- Show sniff and progress -->
+	<arg name="basepath" value="./"/><!-- Strip the file paths down to the relevant bit -->
+	<arg name="colors"/>
+	<arg name="extensions" value="php"/>
+	<!-- Exclude test directories -->
+	<exclude-pattern>tests/*</exclude-pattern>
+	<exclude-pattern>vendor/*</exclude-pattern>
+	<exclude-pattern>fw_files/*</exclude-pattern>
+	<arg name="exclude" value="PSR12.ControlStructures.ControlStructureSpacing"/>
+	<arg value="n"/>
+
+	<!-- Rules: Check PHP version compatibility -->
+	<!-- https://github.com/PHPCompatibility/PHPCompatibility#sniffing-your-code-for-compatibility-with-specific-php-versions -->
+	<config name="testVersion" value="5.6-"/>
+
+	<rule ref="PHPCompatibility"/>
+	<rule ref="PSR12"/>
+</ruleset>
diff --git a/lib/CleantalkSP/Common/Scanner/SignaturesAnalyser/tests/bootstrap.php b/lib/CleantalkSP/Common/Scanner/SignaturesAnalyser/tests/bootstrap.php
new file mode 100644
index 000000000..b3d9bbc7f
--- /dev/null
+++ b/lib/CleantalkSP/Common/Scanner/SignaturesAnalyser/tests/bootstrap.php
@@ -0,0 +1 @@
+<?php
diff --git a/lib/CleantalkSP/Common/Scanner/SignaturesAnalyser/tests/phpunit.xml b/lib/CleantalkSP/Common/Scanner/SignaturesAnalyser/tests/phpunit.xml
new file mode 100644
index 000000000..dbe592172
--- /dev/null
+++ b/lib/CleantalkSP/Common/Scanner/SignaturesAnalyser/tests/phpunit.xml
@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<phpunit
+        bootstrap="bootstrap.php"
+        colors="true"
+        convertErrorsToExceptions="true"
+        convertNoticesToExceptions="true"
+        convertWarningsToExceptions="true"
+        stopOnFailure="true"
+        beStrictAboutOutputDuringTests="true"
+>
+    <testsuites>
+        <testsuite name="CleanTalk SPBCT Heuristic Analyser classes Unit Tests">
+            <directory suffix=".php">./</directory>
+            <exclude>./bootstrap.php</exclude>
+        </testsuite>
+    </testsuites>
+</phpunit>
diff --git a/lib/CleantalkSP/SpbctWP/Scanner/ScannerQueue.php b/lib/CleantalkSP/SpbctWP/Scanner/ScannerQueue.php
index 444203679..807bbf065 100755
--- a/lib/CleantalkSP/SpbctWP/Scanner/ScannerQueue.php
+++ b/lib/CleantalkSP/SpbctWP/Scanner/ScannerQueue.php
@@ -788,7 +788,7 @@ public function countFileSystem($path_to_scan = ABSPATH)
         $init_params  = array(
             'count'           => true,
             'file_exceptions' => 'wp-config.php',
-            'extensions'      => 'php, html, htm, js, php2, php3, php4, php5, php6, php7, phtml, shtml, phar, otc', 'ott',
+            'extensions'      => 'php, html, htm, js, php2, php3, php4, php5, php6, php7, phtml, shtml, phar, [ot.]',
             'files_mandatory' => array(),
             'dir_exceptions'  => array(SPBC_PLUGIN_DIR . 'quarantine')
         );
@@ -835,7 +835,7 @@ public function file_system_analysis($offset = null, $amount = null, $path_to_sc
             'full_hash'             => true,
             'offset'                => $offset,
             'amount'                => $amount,
-            'extensions'            => 'php, html, htm, js, php2, php3, php4, php5, php6, php7, phtml, shtml, phar, otc', 'ott',
+            'extensions'            => 'php, html, htm, js, php2, php3, php4, php5, php6, php7, phtml, shtml, phar, [ot.]',
             'extensions_exceptions' => '', //array('jpg', 'jpeg', 'png', 'gif', 'css', 'txt', 'zip', 'xml', 'json')
             'file_exceptions'       => 'wp-config.php',
             'files_mandatory'       => array(),
diff --git a/lib/CleantalkSP/SpbctWP/Scanner/Surface.php b/lib/CleantalkSP/SpbctWP/Scanner/Surface.php
index be8e5b07a..4e91a1d04 100644
--- a/lib/CleantalkSP/SpbctWP/Scanner/Surface.php
+++ b/lib/CleantalkSP/SpbctWP/Scanner/Surface.php
@@ -222,9 +222,13 @@ public function countFilesInDir($main_path)
                     // Extensions filter
                     if ( $this->ext_except || $this->ext ) {
                         $tmp = explode('.', $path);
+                        $currentFileExtension = $tmp[count($tmp) - 1];
                         if (
-                            ($this->ext_except && in_array($tmp[count($tmp) - 1], $this->ext_except, true)) ||
-                            ($this->ext && ! in_array($tmp[count($tmp) - 1], $this->ext, true))
+                            ! $this->hasFileAllowedExtension(
+                                $currentFileExtension,
+                                $this->ext_except,
+                                $this->ext
+                            )
                         ) {
                             continue;
                         }
@@ -296,9 +300,13 @@ public function getFileStructure($main_path)
                     // Extensions filter
                     if ( $this->ext_except || $this->ext ) {
                         $tmp = explode('.', $path);
+                        $currentFileExtension = $tmp[count($tmp) - 1];
                         if (
-                            ($this->ext_except && in_array($tmp[count($tmp) - 1], $this->ext_except, true)) ||
-                            ($this->ext && ! in_array($tmp[count($tmp) - 1], $this->ext, true))
+                            ! $this->hasFileAllowedExtension(
+                                $currentFileExtension,
+                                $this->ext_except,
+                                $this->ext
+                            )
                         ) {
                             continue;
                         }
@@ -474,4 +482,40 @@ public static function dirIsEmpty($dir)
 
         return true;
     }
+
+    public function filterFileExtensionUsingRegexp($extension, array $extensions)
+    {
+        foreach ($extensions as $extensionItem) {
+            $fsymbol = strpos($extensionItem, '[');
+            $lsymbol = strpos($extensionItem, ']');
+
+            $regexpExpression = substr($extensionItem, $fsymbol, $lsymbol);
+            if ($regexpExpression) {
+                $regexpExpression = '/' . trim($regexpExpression, "][") . '/';
+
+                if (\CleantalkSP\SpbctWP\Helpers\Helper::isRegexp($regexpExpression) && preg_match($regexpExpression, $extension)) {
+                    return true;
+                }
+            }
+        }
+
+        return false;
+    }
+
+    private function hasFileAllowedExtension($currentFileExtension, array $ext_except, array $ext)
+    {
+        if (in_array($currentFileExtension, $ext_except, true)) {
+            return false;
+        }
+
+        if (in_array($currentFileExtension, $ext, true)) {
+            return true;
+        }
+
+        if ($this->filterFileExtensionUsingRegexp($currentFileExtension, $ext)) {
+            return true;
+        }
+
+        return false;
+    }
 }