public function testForm()
    {
        $this->visit('/edit-form');

        self::assertNoFormValue('#form', 'activateMembership'); // checkboxes don't have values when unchecked
        self::assertFormValue('#form', 'trialPeriod', '15');

        $this->client->submitForm('Save', [
            'activateMembership' => 'on',
            'trialPeriod' => '7',
        ]);

        self::assertResponseIsSuccessful();
        self::assertFormValue('#form', 'activateMembership', 'on');
        self::assertFormValue('#form', 'trialPeriod', '7');
    }