diff --git a/codeception.yml b/codeception.yml
new file mode 100644
index 0000000..91a46ff
--- /dev/null
+++ b/codeception.yml
@@ -0,0 +1,15 @@
+actor: Tester
+paths:
+    tests: tests
+    log: tests/_output
+    data: tests/_data
+    helpers: tests/_support
+settings:
+    bootstrap: _bootstrap.php
+    colors: true
+    memory_limit: 1024M
+coverage:
+    enabled: true
+    remote: false
+    include:
+        - lib/*
diff --git a/composer.json b/composer.json
index 5301ed8..21c5726 100644
--- a/composer.json
+++ b/composer.json
@@ -1,19 +1,16 @@
 {
-    "name": "legalthings/authorizer",
-    "description": "Authorizer for HTTP requests",
-    "license": "MIT",
-    "require": {
-        "guzzle/guzzle": "v3.9.3"
-    },
-    "require-dev": {
-        "codeception/specify": "0.4.1",
-        "codeception/phpbuiltinserver": "v1.2.1",
-        "codeception/codeception": "2.0.13",
-        "aws/aws-sdk-php": "^3.12"        
-    },
-    "autoload": {
-        "psr-4": {
-            "LegalThings\\": "src/"
-        }
-    }
+	"name" : "legalthings/authorizer",
+	"description" : "Authorizer for HTTP requests",
+	"license" : "MIT",
+	"require" : {
+		"guzzlehttp/guzzle": "^6.1"
+	},
+	"require-dev" : {
+		"codeception/codeception": "^2.1"
+	},
+	"autoload" : {
+		"psr-4" : {
+			"LegalThings\\" : "src/"
+		}
+	}
 }
diff --git a/src/Authorizer.php b/src/Authorizer.php
index 2d58e0a..ff74ce0 100644
--- a/src/Authorizer.php
+++ b/src/Authorizer.php
@@ -34,13 +34,13 @@ class Authorizer
      *                                   Time restrictions are unix timestamps, but may be omitted 
      * @return string  $encryptedSecret  An utf8_encoded encrypted secret
      */
-    public static function sign($allowedResource, $authzgen)
+    public static function sign($allowedResource, $authzgen, $handler = null)
     {
         if (!isset(self::$globalSecret)) trigger_error('$globalSecret is not set', E_USER_WARNING);
 
         list($cerfiticateUrl, $timeStart, $timeEnd) = explode(';', $authzgen) + [null, null, null];
 
-        $publicKey = self::downloadSigningKey($cerfiticateUrl);
+        $publicKey = self::downloadSigningKey($cerfiticateUrl, ['handler' => $handler]);
 
         $resourceSecret = join(';', [
             $timeStart,
@@ -114,6 +114,10 @@ public static function getPublicKey()
         if (!isset(self::$publicKeyPath)) {
             throw new \RuntimeException('Path to the authorizer public key is not set');
         }
+        
+        if(!file_exists (self::$publicKeyPath)) {
+            throw new \RuntimeException('Path to public key does not exist');
+        }
 
         $publicKey = file_get_contents(self::$publicKeyPath);
         self::assertIsValidKey('public', $publicKey, self::$publicKeyPath);
@@ -131,12 +135,67 @@ protected static function getPrivateKey()
         if (!isset(self::$privateKeyPath)) {
             throw new \RuntimeException('Path to the authorizer private key is not set');
         }
+        
+        if(!file_exists (self::$privateKeyPath)) {
+            throw new \RuntimeException('Path to private key does not exist');
+        }
 
         $privateKey = file_get_contents(self::$privateKeyPath);
         self::assertIsValidKey('private', $privateKey, self::$privateKeyPath);
         
         return $privateKey;
     }
+    
+    /**
+     * Generate a private key
+     * 
+     * @param array $options
+     * @throws RuntimeException
+     * @return string
+     */
+    public static function createPrivateKey($options = []) {
+        
+        if (!isset(self::$privateKeyPath)) {
+            throw new \RuntimeException('Path to the authorizer private key is not set');
+        }
+        
+        if(file_exists (self::$privateKeyPath)) {
+            throw new \RuntimeException('Private key already exists');
+        }
+        
+        $config = array(
+            "digest_alg" => "sha512",
+            "private_key_bits" => 2048,
+            "private_key_type" => OPENSSL_KEYTYPE_RSA,
+        );
+        
+        $config = $options + $config;
+        
+        $res = openssl_pkey_new($config);
+        openssl_pkey_export($res, $key);
+        file_put_contents(self::$privateKeyPath, $key);
+        return $key;
+    }
+    
+    /**
+     * Generate a public based on existing private keyu
+     * @throws \RuntimeException
+     * @return string
+     */
+    public static function createPublicKey() {
+        if (!isset(self::$publicKeyPath)) {
+            throw new \RuntimeException('Path to the authorizer public key is not set');
+        }
+        
+        if(file_exists (self::$publicKeyPath)) {
+            throw new \RuntimeException('Public key already exists');
+        }
+        $privateKey = openssl_get_privatekey(self::getPrivateKey());
+        $pubKey = openssl_pkey_get_details($privateKey);
+        $key = $pubKey["key"];
+        file_put_contents(self::$publicKeyPath, $key);
+        return $key;
+    }
 
     /**
      * Get a public key through a remote url
diff --git a/tests/_bootstrap.php b/tests/_bootstrap.php
new file mode 100644
index 0000000..6c8c4f5
--- /dev/null
+++ b/tests/_bootstrap.php
@@ -0,0 +1,3 @@
+<?php
+
+require_once __DIR__ . '/../vendor/autoload.php';
diff --git a/tests/_data/private_key.pem b/tests/_data/private_key.pem
new file mode 100644
index 0000000..662383f
--- /dev/null
+++ b/tests/_data/private_key.pem
@@ -0,0 +1,28 @@
+-----BEGIN PRIVATE KEY-----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+-----END PRIVATE KEY-----
diff --git a/tests/_data/public_key.pem b/tests/_data/public_key.pem
new file mode 100644
index 0000000..c19d6b1
--- /dev/null
+++ b/tests/_data/public_key.pem
@@ -0,0 +1,9 @@
+-----BEGIN PUBLIC KEY-----
+MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAxPm5u5ywTcJMIBbZO5Ij
+aU/WPnWwMM4tu58Iq2LH/lKrOnSleRmPOP5GGdawmIQHDyiE4QZTiAE5LNdxL8uf
+So8fAdgGAZjxAoBt/tqEE1menW+g8ymHWYxF+9mW7bhew8Jq7jy3VhdA4HdhSj21
+EIEwAYQa2Kj6Lqht4f27hQTcNwrVey1Gfl8AJUip/n2OHfUmFvQv3C3owlGm6jSu
+v/g2Tkm50nnkB4biZ92D/ZUu0zgsVeEkfRzKocoYSm7XW38QngoVnKUgKpul7xuD
+7UrDYAn5O0f1Eq0elY5JS7UTXZHBISsydA0Q6BQGEiYC3ZBBwy00gFF9vGh1znYf
+wQIDAQAB
+-----END PUBLIC KEY-----
diff --git a/tests/_support/UnitHelper.php b/tests/_support/UnitHelper.php
new file mode 100644
index 0000000..dcbc192
--- /dev/null
+++ b/tests/_support/UnitHelper.php
@@ -0,0 +1,10 @@
+<?php
+namespace Codeception\Module;
+
+// here you can define custom actions
+// all public methods declared in helper class will be available in $I
+
+class UnitHelper extends \Codeception\Module
+{
+
+}
diff --git a/tests/_support/UnitTester.php b/tests/_support/UnitTester.php
new file mode 100644
index 0000000..68c09cf
--- /dev/null
+++ b/tests/_support/UnitTester.php
@@ -0,0 +1,26 @@
+<?php
+
+
+/**
+ * Inherited Methods
+ * @method void wantToTest($text)
+ * @method void wantTo($text)
+ * @method void execute($callable)
+ * @method void expectTo($prediction)
+ * @method void expect($prediction)
+ * @method void amGoingTo($argumentation)
+ * @method void am($role)
+ * @method void lookForwardTo($achieveValue)
+ * @method void comment($description)
+ * @method \Codeception\Lib\Friend haveFriend($name, $actorClass = null)
+ *
+ * @SuppressWarnings(PHPMD)
+*/
+class UnitTester extends \Codeception\Actor
+{
+    use _generated\UnitTesterActions;
+
+   /**
+    * Define custom actions here
+    */
+}
diff --git a/tests/_support/_generated/UnitTesterActions.php b/tests/_support/_generated/UnitTesterActions.php
new file mode 100644
index 0000000..73a45c2
--- /dev/null
+++ b/tests/_support/_generated/UnitTesterActions.php
@@ -0,0 +1,344 @@
+<?php  //[STAMP] 8300cff049c767c61c081103713d8ef5
+namespace _generated;
+
+// This class was automatically generated by build task
+// You should not change it manually as it will be overwritten on next build
+// @codingStandardsIgnoreFile
+
+use Codeception\Module\Asserts;
+use Codeception\Module\UnitHelper;
+
+trait UnitTesterActions
+{
+    /**
+     * @return \Codeception\Scenario
+     */
+    abstract protected function getScenario();
+
+    
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Checks that two variables are equal.
+     *
+     * @param        $expected
+     * @param        $actual
+     * @param string $message
+     * @see \Codeception\Module\Asserts::assertEquals()
+     */
+    public function assertEquals($expected, $actual, $message = null) {
+        return $this->getScenario()->runStep(new \Codeception\Step\Action('assertEquals', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Checks that two variables are not equal
+     *
+     * @param        $expected
+     * @param        $actual
+     * @param string $message
+     * @see \Codeception\Module\Asserts::assertNotEquals()
+     */
+    public function assertNotEquals($expected, $actual, $message = null) {
+        return $this->getScenario()->runStep(new \Codeception\Step\Action('assertNotEquals', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Checks that two variables are same
+     *
+     * @param        $expected
+     * @param        $actual
+     * @param string $message
+     * @see \Codeception\Module\Asserts::assertSame()
+     */
+    public function assertSame($expected, $actual, $message = null) {
+        return $this->getScenario()->runStep(new \Codeception\Step\Action('assertSame', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Checks that two variables are not same
+     *
+     * @param        $expected
+     * @param        $actual
+     * @param string $message
+     * @see \Codeception\Module\Asserts::assertNotSame()
+     */
+    public function assertNotSame($expected, $actual, $message = null) {
+        return $this->getScenario()->runStep(new \Codeception\Step\Action('assertNotSame', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Checks that actual is greater than expected
+     *
+     * @param        $expected
+     * @param        $actual
+     * @param string $message
+     * @see \Codeception\Module\Asserts::assertGreaterThan()
+     */
+    public function assertGreaterThan($expected, $actual, $message = null) {
+        return $this->getScenario()->runStep(new \Codeception\Step\Action('assertGreaterThan', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * @deprecated
+     * @see \Codeception\Module\Asserts::assertGreaterThen()
+     */
+    public function assertGreaterThen($expected, $actual, $message = null) {
+        return $this->getScenario()->runStep(new \Codeception\Step\Action('assertGreaterThen', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Checks that actual is greater or equal than expected
+     *
+     * @param        $expected
+     * @param        $actual
+     * @param string $message
+     * @see \Codeception\Module\Asserts::assertGreaterThanOrEqual()
+     */
+    public function assertGreaterThanOrEqual($expected, $actual, $message = null) {
+        return $this->getScenario()->runStep(new \Codeception\Step\Action('assertGreaterThanOrEqual', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * @deprecated
+     * @see \Codeception\Module\Asserts::assertGreaterThenOrEqual()
+     */
+    public function assertGreaterThenOrEqual($expected, $actual, $message = null) {
+        return $this->getScenario()->runStep(new \Codeception\Step\Action('assertGreaterThenOrEqual', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Checks that actual is less than expected
+     *
+     * @param        $expected
+     * @param        $actual
+     * @param string $message
+     * @see \Codeception\Module\Asserts::assertLessThan()
+     */
+    public function assertLessThan($expected, $actual, $message = null) {
+        return $this->getScenario()->runStep(new \Codeception\Step\Action('assertLessThan', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Checks that actual is less or equal than expected
+     *
+     * @param        $expected
+     * @param        $actual
+     * @param string $message
+     * @see \Codeception\Module\Asserts::assertLessThanOrEqual()
+     */
+    public function assertLessThanOrEqual($expected, $actual, $message = null) {
+        return $this->getScenario()->runStep(new \Codeception\Step\Action('assertLessThanOrEqual', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Checks that haystack contains needle
+     *
+     * @param        $needle
+     * @param        $haystack
+     * @param string $message
+     * @see \Codeception\Module\Asserts::assertContains()
+     */
+    public function assertContains($needle, $haystack, $message = null) {
+        return $this->getScenario()->runStep(new \Codeception\Step\Action('assertContains', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Checks that haystack doesn't contain needle.
+     *
+     * @param        $needle
+     * @param        $haystack
+     * @param string $message
+     * @see \Codeception\Module\Asserts::assertNotContains()
+     */
+    public function assertNotContains($needle, $haystack, $message = null) {
+        return $this->getScenario()->runStep(new \Codeception\Step\Action('assertNotContains', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Checks that string match with pattern
+     *
+     * @param string $pattern
+     * @param string $string
+     * @param string $message
+     * @see \Codeception\Module\Asserts::assertRegExp()
+     */
+    public function assertRegExp($pattern, $string, $message = null) {
+        return $this->getScenario()->runStep(new \Codeception\Step\Action('assertRegExp', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Checks that string not match with pattern
+     *
+     * @param string $pattern
+     * @param string $string
+     * @param string $message
+     * @see \Codeception\Module\Asserts::assertNotRegExp()
+     */
+    public function assertNotRegExp($pattern, $string, $message = null) {
+        return $this->getScenario()->runStep(new \Codeception\Step\Action('assertNotRegExp', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Checks that variable is empty.
+     *
+     * @param        $actual
+     * @param string $message
+     * @see \Codeception\Module\Asserts::assertEmpty()
+     */
+    public function assertEmpty($actual, $message = null) {
+        return $this->getScenario()->runStep(new \Codeception\Step\Action('assertEmpty', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Checks that variable is not empty.
+     *
+     * @param        $actual
+     * @param string $message
+     * @see \Codeception\Module\Asserts::assertNotEmpty()
+     */
+    public function assertNotEmpty($actual, $message = null) {
+        return $this->getScenario()->runStep(new \Codeception\Step\Action('assertNotEmpty', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Checks that variable is NULL
+     *
+     * @param        $actual
+     * @param string $message
+     * @see \Codeception\Module\Asserts::assertNull()
+     */
+    public function assertNull($actual, $message = null) {
+        return $this->getScenario()->runStep(new \Codeception\Step\Action('assertNull', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Checks that variable is not NULL
+     *
+     * @param        $actual
+     * @param string $message
+     * @see \Codeception\Module\Asserts::assertNotNull()
+     */
+    public function assertNotNull($actual, $message = null) {
+        return $this->getScenario()->runStep(new \Codeception\Step\Action('assertNotNull', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Checks that condition is positive.
+     *
+     * @param        $condition
+     * @param string $message
+     * @see \Codeception\Module\Asserts::assertTrue()
+     */
+    public function assertTrue($condition, $message = null) {
+        return $this->getScenario()->runStep(new \Codeception\Step\Action('assertTrue', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Checks that condition is negative.
+     *
+     * @param        $condition
+     * @param string $message
+     * @see \Codeception\Module\Asserts::assertFalse()
+     */
+    public function assertFalse($condition, $message = null) {
+        return $this->getScenario()->runStep(new \Codeception\Step\Action('assertFalse', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Checks if file exists
+     *
+     * @param string $filename
+     * @param string $message
+     * @see \Codeception\Module\Asserts::assertFileExists()
+     */
+    public function assertFileExists($filename, $message = null) {
+        return $this->getScenario()->runStep(new \Codeception\Step\Action('assertFileExists', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Checks if file doesn't exist
+     *
+     * @param string $filename
+     * @param string $message
+     * @see \Codeception\Module\Asserts::assertFileNotExists()
+     */
+    public function assertFileNotExists($filename, $message = null) {
+        return $this->getScenario()->runStep(new \Codeception\Step\Action('assertFileNotExists', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Fails the test with message.
+     *
+     * @param $message
+     * @see \Codeception\Module\Asserts::fail()
+     */
+    public function fail($message) {
+        return $this->getScenario()->runStep(new \Codeception\Step\Action('fail', func_get_args()));
+    }
+}
diff --git a/tests/unit.suite.yml b/tests/unit.suite.yml
new file mode 100644
index 0000000..c5bcf4b
--- /dev/null
+++ b/tests/unit.suite.yml
@@ -0,0 +1,11 @@
+class_name: UnitTester
+modules:
+    enabled: 
+        - Asserts
+        - UnitHelper
+        
+coverage:
+    enabled: true
+    remote: false
+    include:
+        - lib/*
\ No newline at end of file
diff --git a/tests/unit/AuthorizerTest.php b/tests/unit/AuthorizerTest.php
new file mode 100644
index 0000000..56af3a3
--- /dev/null
+++ b/tests/unit/AuthorizerTest.php
@@ -0,0 +1,95 @@
+<?php
+use Codeception\TestCase\Test;
+use GuzzleHttp\Handler\MockHandler;
+use GuzzleHttp\HandlerStack;
+use GuzzleHttp\Psr7\Response;
+use LegalThings\Authorizer;
+
+class AuthorizerTest extends Test
+{
+   /**
+    * @var UnitTester
+    */
+    protected $tester;
+    
+    const KEYS_DIR = "tests/keys";
+
+    // executed before each test
+    protected function _before()
+    {
+        mkdir(self::KEYS_DIR, 0700, TRUE);
+        Authorizer::$globalSecret = "testsecret";
+        Authorizer::$privateKeyPath = self::KEYS_DIR . "/private_key.pem";
+        Authorizer::$publicKeyPath = self::KEYS_DIR . "/public_key.pem";
+    }
+
+    // executed after each test
+    protected function _after()
+    {
+        if(file_exists(self::KEYS_DIR . "/private_key.pem")) {
+            unlink(self::KEYS_DIR . "/private_key.pem");
+        }
+        if(file_exists(self::KEYS_DIR . "/public_key.pem")) {
+            unlink(self::KEYS_DIR . "/public_key.pem");
+        }
+        rmdir(self::KEYS_DIR);
+    }
+    
+    public function testGeneratePrivateKey() {
+        
+        $privateKey = Authorizer::createPrivateKey();
+        $this->assertTrue($this->checkKey("private", $privateKey));
+    }
+    
+    public function testGeneratePrivateAndPublicKey() {
+        
+        $privateKey = Authorizer::createPrivateKey();
+        $this->assertTrue($this->checkKey("private", $privateKey));
+        
+        $publicKey = Authorizer::createPublicKey();
+        $this->assertTrue($this->checkKey("public", $publicKey));
+    }
+    
+    public function testGetPublicKey() {
+        
+        Authorizer::$privateKeyPath = "tests/_data/private_key.pem";
+        Authorizer::$publicKeyPath = "tests/_data/public_key.pem";
+        
+        $publicKey = Authorizer::getPublicKey();
+        $this->assertTrue($this->checkKey("public", $publicKey));
+    }
+    
+    public function testSignDecryptingAndVerifying() {
+        
+        Authorizer::$privateKeyPath = "tests/_data/private_key.pem";
+        Authorizer::$publicKeyPath = "tests/_data/public_key.pem";
+        
+        $_SERVER['HTTP_HOST'] = "example.com";
+        
+        $resource = "secret resource";
+        $startTime = time();
+        $endTime = $startTime + 500;
+        
+        $mock = new MockHandler([
+            new Response(200, [], Authorizer::getPublicKey())
+        ]);
+        $handler = HandlerStack::create($mock);
+        $encryptedSecret = Authorizer::sign($resource, "http://example.com/public_key.pem;$startTime;$endTime", $handler);
+        
+        $decrypted = Authorizer::decrypt($encryptedSecret);
+        $values = explode(";", $decrypted);
+        $this->assertEquals($startTime, $values[0]);
+        $this->assertEquals($endTime, $values[1]);
+        
+        $this->assertTrue(Authorizer::verify($resource, $decrypted));
+    }
+    
+    protected function checkKey($type, $key) {
+        if (!preg_match('/^-----BEGIN (RSA |DSA )?' . strtoupper($type) . ' KEY-----/', $key)) {
+            return false;
+        }
+        
+        return true;
+    }
+}
+?>
\ No newline at end of file
diff --git a/tests/unit/UnitTester.php b/tests/unit/UnitTester.php
new file mode 100644
index 0000000..c1e0334
--- /dev/null
+++ b/tests/unit/UnitTester.php
@@ -0,0 +1,300 @@
+<?php //[STAMP] 2e3d1ee5e16d51d7cf2dde60fb907d96
+
+// This class was automatically generated by build task
+// You should not change it manually as it will be overwritten on next build
+// @codingStandardsIgnoreFile
+
+
+use Codeception\Module\Asserts;
+use Codeception\Module\UnitHelper;
+
+/**
+ * Inherited Methods
+ * @method void wantToTest($text)
+ * @method void wantTo($text)
+ * @method void execute($callable)
+ * @method void expectTo($prediction)
+ * @method void expect($prediction)
+ * @method void amGoingTo($argumentation)
+ * @method void am($role)
+ * @method void lookForwardTo($achieveValue)
+ * @method void comment($description)
+ * @method void haveFriend($name, $actorClass = null)
+ *
+ * @SuppressWarnings(PHPMD)
+*/
+class UnitTester extends \Codeception\Actor
+{
+   
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Checks that two variables are equal.
+     *
+     * @param        $expected
+     * @param        $actual
+     * @param string $message
+     *
+     * @return mixed
+     * @see \Codeception\Module\Asserts::assertEquals()
+     */
+    public function assertEquals($expected, $actual, $message = null) {
+        return $this->scenario->runStep(new \Codeception\Step\Action('assertEquals', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Checks that two variables are not equal
+     *
+     * @param        $expected
+     * @param        $actual
+     * @param string $message
+     * @see \Codeception\Module\Asserts::assertNotEquals()
+     */
+    public function assertNotEquals($expected, $actual, $message = null) {
+        return $this->scenario->runStep(new \Codeception\Step\Action('assertNotEquals', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Checks that two variables are same
+     *
+     * @param        $expected
+     * @param        $actual
+     * @param string $message
+     *
+     * @return mixed
+     * @see \Codeception\Module\Asserts::assertSame()
+     */
+    public function assertSame($expected, $actual, $message = null) {
+        return $this->scenario->runStep(new \Codeception\Step\Action('assertSame', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Checks that two variables are not same
+     *
+     * @param        $expected
+     * @param        $actual
+     * @param string $message
+     * @see \Codeception\Module\Asserts::assertNotSame()
+     */
+    public function assertNotSame($expected, $actual, $message = null) {
+        return $this->scenario->runStep(new \Codeception\Step\Action('assertNotSame', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Checks that expected is greater than actual
+     *
+     * @param        $expected
+     * @param        $actual
+     * @param string $message
+     * @see \Codeception\Module\Asserts::assertGreaterThan()
+     */
+    public function assertGreaterThan($expected, $actual, $message = null) {
+        return $this->scenario->runStep(new \Codeception\Step\Action('assertGreaterThan', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * @deprecated
+     * @see \Codeception\Module\Asserts::assertGreaterThen()
+     */
+    public function assertGreaterThen($expected, $actual, $message = null) {
+        return $this->scenario->runStep(new \Codeception\Step\Action('assertGreaterThen', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Checks that expected is greater or equal than actual
+     *
+     * @param        $expected
+     * @param        $actual
+     * @param string $message
+     * @see \Codeception\Module\Asserts::assertGreaterThanOrEqual()
+     */
+    public function assertGreaterThanOrEqual($expected, $actual, $message = null) {
+        return $this->scenario->runStep(new \Codeception\Step\Action('assertGreaterThanOrEqual', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * @deprecated
+     * @see \Codeception\Module\Asserts::assertGreaterThenOrEqual()
+     */
+    public function assertGreaterThenOrEqual($expected, $actual, $message = null) {
+        return $this->scenario->runStep(new \Codeception\Step\Action('assertGreaterThenOrEqual', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Checks that expected is less than actual
+     *
+     * @param        $expected
+     * @param        $actual
+     * @param string $message
+     * @see \Codeception\Module\Asserts::assertLessThan()
+     */
+    public function assertLessThan($expected, $actual, $message = null) {
+        return $this->scenario->runStep(new \Codeception\Step\Action('assertLessThan', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Checks that expected is less or equal than actual
+     *
+     * @param        $expected
+     * @param        $actual
+     * @param string $message
+     * @see \Codeception\Module\Asserts::assertLessThanOrEqual()
+     */
+    public function assertLessThanOrEqual($expected, $actual, $message = null) {
+        return $this->scenario->runStep(new \Codeception\Step\Action('assertLessThanOrEqual', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Checks that haystack contains needle
+     *
+     * @param        $needle
+     * @param        $haystack
+     * @param string $message
+     * @see \Codeception\Module\Asserts::assertContains()
+     */
+    public function assertContains($needle, $haystack, $message = null) {
+        return $this->scenario->runStep(new \Codeception\Step\Action('assertContains', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Checks that haystack doesn't contain needle.
+     *
+     * @param        $needle
+     * @param        $haystack
+     * @param string $message
+     * @see \Codeception\Module\Asserts::assertNotContains()
+     */
+    public function assertNotContains($needle, $haystack, $message = null) {
+        return $this->scenario->runStep(new \Codeception\Step\Action('assertNotContains', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Checks that variable is empty.
+     *
+     * @param        $actual
+     * @param string $message
+     * @see \Codeception\Module\Asserts::assertEmpty()
+     */
+    public function assertEmpty($actual, $message = null) {
+        return $this->scenario->runStep(new \Codeception\Step\Action('assertEmpty', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Checks that variable is not empty.
+     *
+     * @param        $actual
+     * @param string $message
+     * @see \Codeception\Module\Asserts::assertNotEmpty()
+     */
+    public function assertNotEmpty($actual, $message = null) {
+        return $this->scenario->runStep(new \Codeception\Step\Action('assertNotEmpty', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Checks that variable is NULL
+     *
+     * @param        $actual
+     * @param string $message
+     * @see \Codeception\Module\Asserts::assertNull()
+     */
+    public function assertNull($actual, $message = null) {
+        return $this->scenario->runStep(new \Codeception\Step\Action('assertNull', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Checks that variable is not NULL
+     *
+     * @param        $actual
+     * @param string $message
+     * @see \Codeception\Module\Asserts::assertNotNull()
+     */
+    public function assertNotNull($actual, $message = null) {
+        return $this->scenario->runStep(new \Codeception\Step\Action('assertNotNull', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Checks that condition is positive.
+     *
+     * @param        $condition
+     * @param string $message
+     * @see \Codeception\Module\Asserts::assertTrue()
+     */
+    public function assertTrue($condition, $message = null) {
+        return $this->scenario->runStep(new \Codeception\Step\Action('assertTrue', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Checks that condition is negative.
+     *
+     * @param        $condition
+     * @param string $message
+     * @see \Codeception\Module\Asserts::assertFalse()
+     */
+    public function assertFalse($condition, $message = null) {
+        return $this->scenario->runStep(new \Codeception\Step\Action('assertFalse', func_get_args()));
+    }
+
+ 
+    /**
+     * [!] Method is generated. Documentation taken from corresponding module.
+     *
+     * Fails the test with message.
+     *
+     * @param $message
+     * @see \Codeception\Module\Asserts::fail()
+     */
+    public function fail($message) {
+        return $this->scenario->runStep(new \Codeception\Step\Action('fail', func_get_args()));
+    }
+}
diff --git a/tests/unit/_bootstrap.php b/tests/unit/_bootstrap.php
new file mode 100644
index 0000000..8a88555
--- /dev/null
+++ b/tests/unit/_bootstrap.php
@@ -0,0 +1,2 @@
+<?php
+// Here you can initialize variables that will be available to your tests