1. A system comprising: a processor; and a memory comprising instructions that, when executed by the processor, cause the system to at least: store computer-readable instructions for implementing a plurality of web crawlers; receive a test document from a computing device, the test document specifying a test for an object of a web page to determine a quality of the web page, the test document further specifying a user state for browsing the web page, and the test identifying an expected outcome associated with performing an action on the object; store the test document separately from the computer-readable instructions for implementing the plurality of the web crawlers, the test document stored at a network location; select a web crawler from the plurality of web crawlers based at least in part on the user state, the web crawler configured to access the web page and perform the test based at least in part on the test document; execute a respective subset of the computer-readable instructions for implementing the plurality of web crawlers to launch the web crawler; provide the network location and an identifier of the web page to the web crawler, wherein the web crawler accesses the test document from the network location, accesses the web page based at least in part on the identifier and the user state, identifies the object from the test document, and performs the action on the object based at least in part on the test document; receive a result of the test from the web crawler, the result comprising an indication that an outcome different from the expected outcome occurred based at least in part on the action being performed on the object, the result further identifying a second object of the web page not identified in the test document; generate a report indicating the quality of the web page based at least in part on the result, the report including a metric for the object and a second metric for the second object based at least in part on the result, the report further identifying a correction to the object such that the expected outcome occurs when the action is performed; provide the report to the computing device, wherein the web page is updated by at least updating the object according to the correction identified in the report; and receive a second test document for testing the second object based at least in part on the second metric.
2. The system of claim 1 , wherein the object comprises an element of the web page, and wherein the test document comprises a request to at least one of check whether the web page comprises the element or check whether the element has an expected property.