如何安装php单元以及如何使用它

Can anybody please teach me how to install php unit and how to use it in a normal php function like this.....I have searched on Youtube and on google as well most of the way of installing php unit is outdated and none of them teach properly. I am a windows user. Thank You!

class Login extends Connection
{

public $id;
public $username;
public $password;

public function getUsername($USERNAME)
{
$this->username=$USERNAME;
}

public function getPassword($PASSWORD)
{
$this->password=$PASSWORD;
}

public function setUsername($USERNAME)
{
$this->username;
}

public function setPassword($PASSWORD)
{
$this->password;
}

public function login1()
{   

$query="select * from tbl_user where Username='$this->username' && 
Password='$this->password' ";
$res = mysqli_query($this->conn,$query);
$num = mysqli_num_rows($res); //it counts selected rows in database


if($num==1)
{   
echo "logged in";
}
else
{   
echo "failed";

}
}
}