Do you have experience developing with the method of testing by writing tests before code?

Yes, I have used the TDD (Test-Driven Development) approach when developing in PHP. The essence of the method is that first a test is written that describes the expected behavior of a function or class, and then the code that passes this test is written. This approach helps create more reliable and maintainable code, as well as facilitates refactoring.

An example of a simple test using PHPUnit:

class CalculatorTest extends \PHPUnit\Framework\TestCase {
    public function testAdd() {
        $calc = new Calculator();
        $this->assertEquals(4, $calc->add(2, 2));
    }
}

First, this test is written, which, of course, will not pass initially, then the add method is implemented so that the test becomes successful.