diff --git a/src/application/config/hooks.php b/src/application/config/hooks.php
index 6c6fb6cf..dfbb0be8 100644
--- a/src/application/config/hooks.php
+++ b/src/application/config/hooks.php
@@ -9,14 +9,6 @@
 |	http://codeigniter.com/user_guide/general/hooks.html
 |
 */
-// This hook is necessary to make the phpunit work with 
-// the codeigniter framework.
-$hook['display_override'] = array(
-	'class' => 'DisplayHook',
-	'function' => 'captureOutput',
-	'filename' => 'DisplayHook.php',
-	'filepath' => 'hooks'
-);
 
 /* End of file hooks.php */
 /* Location: ./application/config/hooks.php */
\ No newline at end of file
diff --git a/src/application/controllers/test.php b/src/application/controllers/test.php
new file mode 100644
index 00000000..fc3f61cd
--- /dev/null
+++ b/src/application/controllers/test.php
@@ -0,0 +1,38 @@
+<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
+
+class Test extends CI_Controller {
+    /**
+     * Class Constructor
+     */
+    public function __construct() {
+        parent::__construct();
+        $this->load->driver('Unit_tests');
+    }
+    
+    /**
+     * Run all available unit tests.
+     */
+    public function index() {
+        $this->load->view('general/test');
+        $this->unit_tests->run_all_tests();
+    } 
+    
+    /**
+     * Test only the app models.
+     */
+    public function models() {
+        $this->load->view('general/test');
+        $this->unit_tests->run_model_tests();
+    }
+    
+    /**
+     * Test only the app libraries.
+     */
+    public function libraries() {
+        $this->load->view('general/test');
+        $this->unit_tests->run_library_tests();
+    }
+}
+
+/* End of file test.php */
+/* Location: ./application/controllers/test.php */
\ No newline at end of file
diff --git a/src/application/helpers/custom_exceptions_helper.php b/src/application/helpers/custom_exceptions_helper.php
new file mode 100644
index 00000000..482f13a2
--- /dev/null
+++ b/src/application/helpers/custom_exceptions_helper.php
@@ -0,0 +1,14 @@
+<?php
+
+/**
+ * Database Exception Class
+ */
+class DatabaseException extends Exception {}
+
+/**
+ * Validation Exception Class
+ */
+class ValidationException extends Exception {}
+
+/* End of file exception_types_helper.php */
+/* Location: ./application/helpers/exception_types_helper.php */
\ No newline at end of file
diff --git a/src/application/helpers/data_validation_helper.php b/src/application/helpers/data_validation_helper.php
new file mode 100644
index 00000000..07bbdb92
--- /dev/null
+++ b/src/application/helpers/data_validation_helper.php
@@ -0,0 +1,18 @@
+<?php
+
+/**
+ * Check if a string date is valid for insertion or update 
+ * to the database. 
+ * 
+ * @param string $datetime The given date.
+ * @return bool Returns the validation result.
+ * 
+ * @link http://stackoverflow.com/a/8105844/1718162 [SOURCE]
+ */
+function validate_mysql_datetime($datetime) {
+    $dt = DateTime::createFromFormat('Y-m-d H:i:s', $datetime);
+    return ($dt) ? TRUE : FALSE;
+}
+
+/* End of file data_validation_helper.php */
+/* Location: ./application/helpers/data_validation_helper.php */
\ No newline at end of file
diff --git a/src/application/helpers/general_helper.php b/src/application/helpers/general_helper.php
index 1193f85c..0066474a 100644
--- a/src/application/helpers/general_helper.php
+++ b/src/application/helpers/general_helper.php
@@ -25,5 +25,5 @@ function date3339($timestamp=0) {
     return $date;
 }
 
-/* End of file general.php */
-/* Location: ./application/helpers/general.php */
\ No newline at end of file
+/* End of file general_helper.php */
+/* Location: ./application/helpers/general_helper.php */
\ No newline at end of file
diff --git a/src/application/hooks/DisplayHook.php b/src/application/hooks/DisplayHook.php
deleted file mode 100644
index 3427d65f..00000000
--- a/src/application/hooks/DisplayHook.php
+++ /dev/null
@@ -1,12 +0,0 @@
-<?php
-// This hook is necessary in order to run php unit tests
-// against the codeigniter framework.
-class DisplayHook {
-	public function captureOutput() {
-		$this->CI =& get_instance();
-		$output = $this->CI->output->get_output();
-		if (ENVIRONMENT != 'testing') {
-			echo $output;
-		}
-	}
-}
\ No newline at end of file
diff --git a/src/application/libraries/Unit_tests/Unit_tests.php b/src/application/libraries/Unit_tests/Unit_tests.php
new file mode 100644
index 00000000..7848429e
--- /dev/null
+++ b/src/application/libraries/Unit_tests/Unit_tests.php
@@ -0,0 +1,54 @@
+<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed'); 
+
+/**
+ * Unit testing driver.
+ * 
+ * This driver handles all the unit testing of the application. 
+ * Custom methods (test categories) can be created in order to 
+ * use different test groups on each testing
+ */
+class Unit_tests extends CI_Driver_Library {
+    public $CI;
+    public $valid_drivers;
+    
+    /**
+     * Class Constructor
+     */
+    public function __construct() {
+        $this->CI =& get_instance();
+        // Add more subclasses to the following array to expand
+        // the unit testing classes.
+        $this->valid_drivers = array(
+            'Unit_tests_appointments_model'
+        );
+    }
+    
+    /**
+     * Run all the available tests of the system. 
+     * 
+     * If a new group of tests is added, it should be also added in
+     * this method, in order to be executed when all the tests need to 
+     * be run.
+     */
+    public function run_all_tests() {
+        $this->run_model_tests();
+        $this->run_library_tests();
+    }
+    
+    ///////////////////////////////////////////////////////////////////////////
+    // UNIT TEST GROUPS
+    ///////////////////////////////////////////////////////////////////////////
+    /**
+     * Run all the models tests.
+     */
+    public function run_model_tests() {
+        $this->appointments_model->run_all();
+    }
+    
+    /**
+     * Run all the library tests.
+     */
+    public function run_library_tests() {
+        
+    }   
+}
\ No newline at end of file
diff --git a/src/application/libraries/Unit_tests/drivers/Unit_tests_appointments_model.php b/src/application/libraries/Unit_tests/drivers/Unit_tests_appointments_model.php
new file mode 100644
index 00000000..b46fd542
--- /dev/null
+++ b/src/application/libraries/Unit_tests/drivers/Unit_tests_appointments_model.php
@@ -0,0 +1,200 @@
+<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed'); 
+
+class Unit_tests_appointments_model extends CI_Driver {
+    private $CI;
+    
+    private $provider_id;
+    private $customer_id;
+    private $service_id;
+    
+    /**
+     * Class Constructor
+     */
+    public function __construct() {
+        $this->CI =& get_instance();
+        
+        $this->CI->load->library('Unit_test');
+        $this->CI->load->model('Appointments_Model');
+        
+        // Get some sample data from the database (will be needed in the 
+        // testing methods).
+        $this->provider_id = $this->CI->db
+                                        ->select('ea_users.id')
+                                        ->from('ea_users')
+                                        ->join('ea_roles', 'ea_roles.id = ea_users.id_roles', 'inner')
+                                        ->where('ea_roles.slug', DB_SLUG_PROVIDER)
+                                        ->get()->row()->id;   
+        $this->service_id = $this->CI->db
+                                        ->select('ea_services.id')
+                                        ->from('ea_services')
+                                        ->join('ea_services_providers', 'ea_services_providers.id_services = ea_services.id', 'inner')
+                                        ->where('ea_services_providers.id_users', $this->provider_id)
+                                        ->get()->row()->id;
+        $this->customer_id = $this->CI->db
+                                        ->select('ea_users.id')
+                                        ->from('ea_users')
+                                        ->join('ea_roles', 'ea_roles.id = ea_users.id_roles', 'inner')
+                                        ->where('ea_roles.slug', DB_SLUG_CUSTOMER)
+                                        ->get()->row()->id;  
+    }
+    
+    /**
+     * Run all the available tests
+     */
+    public function run_all() {
+        // All the methods whose names start with "test" are going to be 
+        // executed. If you want a method to not be executed remove the 
+        // "test" keyword from the beginning.
+        $class_methods = get_class_methods('Unit_tests_appointments_model');
+        foreach ($class_methods as $method_name) {
+            if (strpos($method_name, 'test_') !== FALSE) {
+                call_user_func(array($this, $method_name));
+            }
+        }
+        
+        // Create a report on the browser.
+        $this->CI->output->append_output($this->CI->unit->report());
+    }
+    
+    /////////////////////////////////////////////////////////////////////////
+    // UNIT TESTS
+    /////////////////////////////////////////////////////////////////////////    
+    /**
+     * Test the appointment add method - insert new record.
+     */
+    private function test_add_appointment_insert() {
+        // Add - insert new appointment record to the database.
+        $appointment_data = array(
+                               'start_datetime' => '2013-05-01 12:30:00',
+                               'end_datetime' => '2013-05-01 13:00:00',
+                               'notes' => 'Some notes right here...',
+                               'id_users_provider' => $this->provider_id,
+                               'id_users_customer' => $this->customer_id,
+                               'id_services' => $this->service_id
+                           );
+        $appointment_data['id'] = $this->CI->Appointments_Model->add($appointment_data);
+        $this->CI->unit->run($appointment_data['id'], 'is_int', 'Test if add() appointment (insert operation) returned the db row id.');
+        
+        // Check if the record is the one that was inserted.
+        $db_data = $this->CI->db->get_where('ea_appointments', array('id' => $appointment_data['id']))->row_array();
+        $this->CI->unit->run($appointment_data, $db_data, 'Test if add() appointment (insert operation) has successfully inserted a record.');
+
+        // Delete inserted record.
+        $this->CI->db->delete('ea_appointments', array('id' => $appointment_data['id']));
+    }
+    
+    /**
+     * Test the appointment add method - update existing record.
+     */
+    private function test_add_appointment_update() {
+        // Insert new appointment (this row will be updated later).
+        $appointment_data = array(
+                               'start_datetime' => '2013-05-01 12:30:00',
+                               'end_datetime' => '2013-05-01 13:00:00',
+                               'notes' => 'Some notes right here...',
+                               'id_users_provider' => $this->provider_id,
+                               'id_users_customer' => $this->customer_id,
+                               'id_services' => $this->service_id
+                           );
+        $this->CI->db->insert('ea_appointments', $appointment_data);
+        $appointment_data['id'] = $this->CI->db->insert_id();
+        
+        // Perform the update operation and check if the record is update.
+        $changed_notes = 'Some CHANGED notes right here ...';
+        $appointment_data['notes'] = $changed_notes;
+        
+        $update_result = $this->CI->Appointments_Model->add($appointment_data);
+        $this->CI->unit->run($update_result, 'is_int', 'Test if add() appointment (update operation) has returned the row id.');
+        
+        $db_notes = $this->CI->db->get_where('ea_appointments', array('id' => $update_result))->row()->notes;
+        $this->CI->unit->run($changed_notes, $db_notes, 'Test add() appointment (update operation) has successfully updated record.');
+        
+        // Delete inserted record.
+        $this->CI->db->delete('ea_appointments', array('id' => $appointment_data['id']));
+    }
+    
+    /**
+     * Test appointment data insertion with wrong date 
+     * format for the corresponding datetime db fields.
+     */
+    private function test_add_appointment_wrong_date_format() {
+        // Insert new appointment with no foreign keys.
+        $appointment_data = array(
+                                'start_datetime' => '2013-0WRONG5-01 12:30WRONG:00',
+                                'end_datetime' => '2013-0WRONG5-01WRONG 13:00WRONG:00',
+                                'notes' => 'Some notes right here...',
+                                'id_users_provider' => $this->provider_id,
+                                'id_users_customer' => $this->customer_id,
+                                'id_services' => $this->service_id
+                             );
+        
+        $hasThrownException = FALSE; // This method must throw a validation exception.
+        try {
+            $this->CI->Appointments_Model->add($appointment_data);
+        } catch(ValidationException $valExc) {
+            $hasThrownException = TRUE;
+        }
+        
+        $this->CI->unit->run($hasThrownException, TRUE, 'Test add() appointment with wrong date format.', 'A validation exception must be thrown.');
+    }
+    
+    /**
+     * Test the exists() method. 
+     * 
+     * Insert a new appointment and test if it exists.
+     */
+    private function test_appointment_exists() {
+        // Insert new appointment (this row will be checked later).
+        $appointment_data = array(
+                               'start_datetime' => '2013-05-01 12:30:00',
+                               'end_datetime' => '2013-05-01 13:00:00',
+                               'notes' => 'Some notes right here...',
+                               'id_users_provider' => $this->provider_id,
+                               'id_users_customer' => $this->customer_id,
+                               'id_services' => $this->service_id
+                           );
+        $this->CI->db->insert('ea_appointments', $appointment_data);
+        $appointment_data['id'] = $this->CI->db->insert_id();
+        
+        // Test the exists() method
+        $this->CI->unit->run($this->CI->Appointments_Model->exists($appointment_data), TRUE, 'Test exists() method with an inserted record.');
+        
+        // Delete inserted record.
+        $this->CI->db->delete('ea_appointments', array('id' => $appointment_data['id']));
+    }
+    
+    private function test_appointment_does_not_exist() {
+        // Create random appointmnet data that doesn't exist in the database.
+        $appointment_data = array(
+                               'start_datetime' => '2013-05-01 08:33:45',
+                               'end_datetime' => '2013-05-02 13:13:13',
+                               'notes' => 'This is totally random!',
+                               'id_users_provider' => '198678',
+                               'id_users_customer' => '194702',
+                               'id_services' => '8766293'
+                           );
+        
+        $this->CI->unit->run($this->CI->Appointments_Model->exists($appointment_data), FALSE, 'Test exists() method with an appointment that does not exist');
+    }
+    
+    private function test_appointment_exists_wrong_data() {
+        // Create random appointmnet data that doesn't exist in the database.
+        $appointment_data = array(
+                               'start_datetime' => '2WRONG013-05-01 0WRONG8:33:45',
+                               'end_datetime' => '2013-0WRONG5-02 13:13:WRONG13',
+                               'notes' => 'This is totally random!',
+                               'id_users_provider' => '1986WRONG78',
+                               'id_users_customer' => '1WRONG94702',
+                               'id_services' => '876WRONG6293'
+                           );
+        
+        $this->CI->unit->run($this->CI->Appointments_Model->exists($appointment_data), FALSE, 'Test exists() method with wrong appointment data.');
+    }
+    
+    // @task Test find_record_id
+    // @task Test delete 
+    // @task Test get_batch
+    // @task Test get_row
+    // @task Test get_value
+    // @task Test validate_data
+}
\ No newline at end of file
diff --git a/src/application/models/appointments_model.php b/src/application/models/appointments_model.php
index 4050df2e..fe82de27 100644
--- a/src/application/models/appointments_model.php
+++ b/src/application/models/appointments_model.php
@@ -6,6 +6,7 @@ class Appointments_Model extends CI_Model {
      */
     public function __construct() {
         parent::__construct();
+        $this->load->helper('custom_exceptions');
     }
     
     /**
@@ -15,26 +16,27 @@ class Appointments_Model extends CI_Model {
      * appointment doesn't exists it is going to be inserted, otherwise 
      * the record is going to be updated.
      * 
+     * @expectedException ValidationException
+     * @expectedException DatabaseException
+     * 
      * @param array $appointment_data Associative array with the appointmet's 
      * data. Each key has the same name with the database fields.
      * @return int Returns the appointments id.
      */
     public function add($appointment_data) {
-        try {
-            $appointment_id = $this->exists($appointment_data);
-            
-            if (!$appointment_id) {
-                $appointment_id = $this->insert($appointment_data);
-            } else {
-                $appointment_data['id'] = $appointment_id;
-                $this->update($appointment_data);
-            }
-            
-            return $appointment_id;
-            
-        } catch (Exception $exc) {
-            echo $exc->getMessage() . '<br/><pre>' . $exc->getTraceAsString() . '</pre>';
+        // Validate the appointment data before doing anything.
+        if (!$this->validate_data($appointment_data)) {
+            throw new ValidationException('Appointment data are not valid');
         }
+
+        // Insert or update the appointment data.
+        if (!$this->exists($appointment_data)) {
+            $appointment_data['id'] = $this->insert($appointment_data);
+        } else {
+            $appointment_data['id'] = $this->update($appointment_data);
+        }
+
+        return $appointment_data['id'];
     }
     
     /**
@@ -44,36 +46,35 @@ class Appointments_Model extends CI_Model {
      * the database. This method does not search with the id, but with a
      * combination of the appointments field values.
      * 
+     * @uses find_record_id() 
+     * 
      * @param array $appointment_data Associative array with the appointment's
      * data. Each key has the same name with the database fields.
-     * @return int|bool Returns the record id or FALSE if it doesn't exist.
+     * @return bool Returns wether the record exists or not.
      */
-    public function exists($appointment_data) {
-        $this->db->where(array(
-            'start_datetime'    => $appointment_data['start_datetime'],
-            'end_datetime'      => $appointment_data['end_datetime'],
-            'id_users_provider' => $appointment_data['id_users_provider'],
-            'id_users_customer' => $appointment_data['id_users_customer'],
-            'id_services'       => $appointment_data['id_services']
-        ));
-        
-        $result = $this->db->get('ea_appointments');
-        
-        return ($result->num_rows() > 0) ? $result->row()->id : FALSE;
+    public function exists($appointment_data) {   
+        try {
+            $this->find_record_id($appointment_data);
+            return TRUE;
+        } catch(DatabaseException $dbExc) {
+            return FALSE;
+        }
     }
     
     /**
      * Insert a new appointment record to the database.
      * 
+     * @expectedException DatabaseException
+     * 
      * @param array $appointment_data Associative array with the appointment's
      * data. Each key has the same name with the database fields.
      * @return int Returns the id of the new record.
      */
     private function insert($appointment_data) {
         if (!$this->db->insert('ea_appointments', $appointment_data)) {
-            throw new Exception('Could not insert new appointment record.');
+            throw new DatabaseException('Could not insert appointment record.');
         }
-        return $this->db->insert_id();
+        return intval($this->db->insert_id());
     }
     
     /**
@@ -84,12 +85,77 @@ class Appointments_Model extends CI_Model {
      * 
      * @param array $appointment_data Associative array with the appointment's
      * data. Each key has the same name with the database fields.
-     * @return @return int Returns the id of the updated record.
+     * @return int Returns the id of the updated record.
      */
     private function update($appointment_data) {
+        if (!isset($appointment_data['id'])) {
+            $appointment_data['id'] = $this->find_record_id($appointment_data);
+        }
+        
         $this->db->where('id', $appointment_data['id']);
         if (!$this->db->update('ea_appointments', $appointment_data)) {
-            throw new Exception('Could not update appointment record.');
+            throw new DatabaseException('Could not update appointment record.');
+        }
+        
+        return $appointment_data['id'];
+    }
+    
+    /**
+     * Find the database id of an appointment record. 
+     * 
+     * The appointment data should include the following fields in order to 
+     * get the unique id from the database: start_datetime, end_datetime, 
+     * id_users_provider, id_users_customer, id_services.
+     * 
+     * @expectedException DatabaseException
+     * 
+     * @param array $appointment_data Array with the appointment data. The 
+     * keys of the array should have the same names as the db fields.
+     * @return int Returns the id.
+     */
+    public function find_record_id($appointment_data) {
+        $this->db->where(array(
+            'start_datetime'    => $appointment_data['start_datetime'],
+            'end_datetime'      => $appointment_data['end_datetime'],
+            'id_users_provider' => $appointment_data['id_users_provider'],
+            'id_users_customer' => $appointment_data['id_users_customer'],
+            'id_services'       => $appointment_data['id_services']
+        ));
+        
+        $result = $this->db->get('ea_appointments');
+
+        if ($result->num_rows() == 0) {
+            throw new DatabaseException('Could not find appointment record id.');
+        }
+        
+        return $result->row()->id;
+    }
+    
+    /**
+     * Validate appointment data before the insert or 
+     * update operation is executed.
+     * 
+     * @param array $appointment_data Contains the appointment data.
+     * @return boolean Returns the validation result.
+     */
+    public function validate_data($appointment_data) {
+        $this->load->helper('data_validation');
+        
+        try {
+            // Check if appointment dates are valid.
+            if (!validate_mysql_datetime($appointment_data['start_datetime'])) {
+                throw new Exception('Appointment start datetime is invalid.');    
+            }
+            
+            if (!validate_mysql_datetime($appointment_data['end_datetime'])) {
+                throw new Exception('Appointment end datetime is invalid.');
+            }
+
+            // @task Check if appointment foreign keys are valid.
+            
+            return TRUE;
+        } catch (Exception $exc) {
+            return FALSE;
         }
     }
     
diff --git a/src/application/views/general/test.php b/src/application/views/general/test.php
new file mode 100644
index 00000000..bbc706a5
--- /dev/null
+++ b/src/application/views/general/test.php
@@ -0,0 +1,45 @@
+<script type="text/javascript" src="<?php echo $this->config->base_url(); ?>assets/js/libs/jquery/jquery.min.js"></script>
+<script type="text/javascript">
+    $(document).ready(function() {
+        var passedTestsNumber = $('span').filter(function() {
+                                    return $(this).text() === 'Passed';
+                                }).length;
+        var totalTestsNumber = $('table').length;
+        
+        $('#test-results').text(passedTestsNumber + ' / ' + totalTestsNumber + ' Passed');
+        
+        if (passedTestsNumber == totalTestsNumber) {
+            $('#test-header').css('background-color', '#3DD481');
+        } else {
+            $('#test-header').css('background-color', '#D43D3D');
+        }
+    });
+</script>
+
+<style>
+    #test-header {
+        font-size: 30px;
+        font-family: arial, sans-serif;
+        height: 70px; 
+        padding: 10px;
+        margin-bottom: 15px;
+    }
+    
+    #test-heading {
+        margin-top: 15px;
+        display: inline-block;
+        margin-right: 21px;
+        color: #DBFFA6;
+/*        color: #C0FFD9;
+        text-shadow: 0px 1px 1px #0D9E41;*/
+    }
+    
+    #test-results {
+        color: #FFF;
+    }
+</style>
+
+<div id="test-header">
+    <strong id="test-heading">Easy!Appointments Unit Testing</strong>
+    <strong id="test-results"></strong>
+</div>
\ No newline at end of file
diff --git a/src/configuration.php b/src/configuration.php
index 4fae61ab..7ebebd4e 100644
--- a/src/configuration.php
+++ b/src/configuration.php
@@ -1,7 +1,7 @@
 <?php
 class SystemConfiguration {
     // General Settings
-    public static $base_url    = 'http://localhost/dev/external/Easy!Appointments/trunk/src/';
+    public static $base_url    = 'http://localhost/dev/external/easy_appointments/trunk/src/';
     
     // Database Settings
     public static $db_host     = 'localhost';
diff --git a/src/system/core/Utf8.php b/src/system/core/Utf8.php
index 21544159..2a27d1f3 100644
--- a/src/system/core/Utf8.php
+++ b/src/system/core/Utf8.php
@@ -38,8 +38,7 @@ class CI_Utf8 {
 	{
 		log_message('debug', "Utf8 Class Initialized");
 
-		//global $CFG;
-		$CFG =& load_class('Config', 'core'); // This is changed due to php unit conflict : http://www.jamesfairhurst.co.uk/posts/view/codeigniter_phpunit_and_netbeans
+		global $CFG;
 
 		if (
 			preg_match('/./u', 'é') === 1					// PCRE must support UTF-8