drupalGet('/js_ajax_test'); $this->click('#edit-test-button'); $this->assertSession() ->waitForElement('css', '#js_ajax_test_form_element'); $elements = $this->cssSelect('#js_ajax_test_form_element'); $this->assertCount(1, $elements); $json = $elements[0]->getText(); $data = json_decode($json, TRUE); $this->assertEquals([ 'element_settings' => 'catbro', 'elementSettings' => 'catbro', ], $data); } }