Schema.org structured data helps you to highlight specific information for search engines and to improve the way your page displays in SERPs. I have compiled a list of tools you might find helpful for testing structured data markup and rich snippet display (microdata, RDFa, RDFa Lite and JSON-LD).

• Google Structured Data Testing Tool — The Structured Data Testing Tool (SDTT) provides a variety of ways to develop, test, and modify your structured markup. You can load markup into the tool either directly or by supplying a URL.
• Yandex Structured data validator — The validator lets you check all the most common microformats: microdata, schema.org, microformats, OpenGraph and RDF. However, not all formats support special snippets or the use of annotated data.
• Bing Markup Validator — Try Markup Validator and validate the markup you have added to your web pages including HTML Microdata, Microformats, RDFa, Schema.org.
• JSON-LD Playground — Play around with JSON-LD markup by typing out some JSON below and seeing what gets generated from it at the bottom of the page. Pick any of the examples below to get started. The playground uses the jsonld.js JSON-LD processor which fully conforms to the JSON-LD Syntax and API specifications.
• RDFa Play — Paste your HTML+RDFa code and preview data visualization. You can also see the raw data by clicking on the “Raw Data” tab.
• Facebook Debugger — You can use the Sharing Debugger to see the information that is used when your website content is shared on Facebook, Messenger and other places. The Batch Invalidator will let you refresh this information for multiple URLs at the same time. Open Graph markup lets you take control over how your website content appears to others.
• Google Email Markup Tester — Empower your emails using schema.org markup.
• RDF Translator — RDF Translator is a multi-format conversion tool for structured markup. It provides translations between data formats ranging from RDF/XML to RDFa or Microdata. The service allows for conversions triggered either by URI or by direct text input. Furthermore it comes with a straightforward REST API for developers.
• Structured Data Linter — The Structured Data Linter is a tool aiding webmasters and web developers to verify the structured data present in their HTML pages. Search engines use structured data to understand webpages more accurately and to present enhanced search results. The Linter understands the microdata, JSON-LD and RDFa formats according to their latest specifications.
• Microdata Tool — A little jQuery drop-in script that you can include on your page and have a handy browser/validator handy, even without Internet connectivity or even a web server.
• Mida — Mida is a Microdata extractor/parser library for Ruby.
• Google Structured Data Markup Helper — This tool will help you add structured-data markup to a sample web page.
• Microdata Generator — Schema.org Generator.
• Web Code Tools — The ultimate web code generator (HTML, CSS, Microdata, Twitter Cards, Open Graph).
• Microdata Generator — Easy to use Microdata Generator for adding Schema.org tags to your site.
• JSON LD Site Name Generator — With this site name json ld generator you can easily generate a Strucure data snippet and add it to your website.
• JSON-LD Schema Generator For SEO — With this tool you can quickly generate the correct JSON-LD for any page on your site.
• RDFa-Lab Bookmarklets — Save these as bookmarks, then activate when on an appropriate page to trigger their effect.
• Schema.org Visualizer — A visualizer for Schema.org.
• Structured Data Testing Tool — This Google Chrome extension uses the Google Structured Data Testing Tool to validate your structured data markup and rich snippets. The Structured Data Testing Tool checks all metadata formats supported by the Google Structured Data Testing Tool including microdata, Schema, RDFa and JSON-LD.