Accessibility testing tools scan your website for accessibility issues that may indicate a violation of the Web Content Accessibility Guidelines (WCAG). However, neither the Department of Justice nor legislation has formally defined ADA compliance. Often, companies and courts ruling on ADA compliance for websites will default to the WCAG as the standard. Much of the WCAG focuses on items that can't be detected using an automated test. While you can and should use automated testing as part of your accessibility program to detect potential issues, you should always include manual review and user testing with members of the disability community as well.