Unit Testing

[benanamen]

As I get more into OOP it appears I should know and understand unit testing and write tests. Since everything I do is DB driven, nearly all an apps functionality requires a database.

 

From what I read, if you are actually connecting to a DB you are not really doing unit testing, so my question is, how do you do a unit test on a method that gets its data from a DB?

 

Here is the current class I am experimenting with. As I understand it, a unit test is for ONE method. How would I do a unit test for example on the select_user method?

class User
    {
    /**
     * @var PDO The connection to the database
     */
    protected $pdo;
    protected $row;
    protected $error;
    protected $password_hash;

    /**
     * Construct.
     * @param PDO $pdo The database connection
     */
    public function __construct($pdo)
        {
        $this->pdo = $pdo;
        }

    /**
     * @param $request: $_POST or $_GET
     * @param $columns: Columns to SELECT
     */
    public function select_user($request, $columns)
        {
        $sql = "SELECT ";
        foreach ($columns AS $field)
            {
            $sql .= $field . ', ';
            }
        $sql = rtrim($sql, ", ");
        $sql .= ' FROM users WHERE username = ?';
        $stmt = $this->pdo->prepare($sql);
        $stmt->execute(array(
            $request
        ));
        $row = $stmt->fetch(PDO::FETCH_ASSOC);

        // No match, Do stuff.
        if (!$stmt->rowCount())
            {
            $this->error['username'] = 'Bad User Name';
            }
        else
            {
            $this->username      = $row['username'];
            $this->password_hash = $row['password'];
            }
        } // End function select_user


    public function verify_password($password)
        {
        if (isset($this->password_hash))
            {
            if (password_verify($password, $this->password_hash))
                {
                echo 'Valid User'; // Set $_SESSION['logged_in'];
                }
            else
                {
                $this->error['password'] = 'Bad Password';
                }
            }
        }

    public function check_errors()
        {
        if (count($this->error) > 0)
            {
            echo 'Errors<br>';
            echo $error = implode("<br >\n", $this->error) . "\n";
            die;
            }
        } // End function check_errors

    } // End Class User

[Jacques1]

From what I read, if you are actually connecting to a DB you are not really doing unit testing, so my question is, how do you do a unit test on a method that gets its data from a DB?

 

By using a mock object instead of an actual PDO instance.

 

But before jumping to advanced unit tests, I'd start with the basics (i. e. writing tests for a class without dependencies).