How to use GitHub Copilot: What it can do and real-world examples

Writing unit tests requires knowing the limits, edge cases, and what might cause failures in your code. Since Copilot knows about your project on GitHub and what you’re working on in your IDE, it can create unit tests to help you.

To do this, select a given block of code. Then either right-click and use the context menu or the /tests slash command. Copilot will then analyze your code and try to provide suggestions for valid inputs, edge cases, and invalid inputs.

For additional guidance on using GitHub Copilot to create unit tests, check out this this docs page of sample prompts.

Explain and document existing code

You can tap into GitHub Copilot’s knowledge of coding patterns to ask it to help explain how a block of code works. This is particularly useful if you’re onboarding to a new project, especially if it’s in a language you don’t have a lot of experience in.

To use this feature, select some code and use either the context menu or the /explain slash command. Copilot will then explain what the code is doing—and then generate documentation on it with another prompt.

This isn’t just useful for onboarding or making sure you understand a piece of code. You can also use this as a building block for other tasks such as helping to translate code from one language to another.

For some sample prompts, check out our docs on explaining complex logic.

Upgrading a framework you’re working with

If you’re tasked with upgrading a codebase to a new version of a framework, it’s not as easy as recompiling the project in the new version. That often results in several errors that you need to track down and resolve. GitHub Copilot can help you here.

You can just ask why your code is producing errors. From there, you can have Copilot provide suggestions on how to fix your code to make it compliant with the new version of the framework. Then ask Copilot for suggestions on how to update the code to fit in a new framework.

Explain a codebase (or a repository on GitHub)

Trying to understand a new codebase? Ask Copilot what a repository does or to summarize key components and it will provide a summary. To get started, click the Copilot icon in the top-right corner of your screen and ask a question. You can also prompt Copilot to debug your workflows with GitHub Actions. If you want to focus Copilot’s attention, you can highlight individual files or folders in a repository, too.

💡 Pro tip: Use Copilot as a chat assistant directly on github.com with a full, natural-language interface.

Translate code to a new language

Let’s say you need to migrate legacy software from COBOL to a more modern coding language. GitHub Copilot can help you with this, even if you don’t have a lot of experience with the source language.

First, ask it to explain what some code is doing, and then use that explanation to create code in the destination language that performs the same functionality. You can also ask it to provide suggestions on how to write the code in the destination language.

Our documentation on explaining legacy code includes a sample prompt and walks through the first portion of this scenario.

Generate documentation

Closely tied to the idea of explaining how code works, you can ask GitHub Copilot to generate documentation for sections of code or entire projects. This can be incredibly useful, and a huge time saver.

In Copilot Free, you can also ask it to provide a summary of given code blocks within your IDE by using the slash command /docs. In the paid versions, you can also generate documentation from issues and pull requests.

One real-world example of this involves legacy COBOL-based applications. You can ask Copilot to help provide the missing docs for a given project. (Visit documenting legacy code to get started).

Debugging code

We’ve all been there—you have a section of code that’s spitting out an error and you aren’t sure how to fix it. Sometimes you try to implement a fix, and then you get more errors (classic 🤦).

To get help from GitHub Copilot, highlight the code in question and either right-click and select “Copilot” or use the /fix slash command in Copilot Chat. You can also ask Copilot Chat why something isn’t working to start a conversation about what the problem might be.

Copilot works by analyzing your code and drawing upon its training data. It also looks at the context of your larger project to identify patterns that might be causing the problem.

To learn more, you can find a sample prompt and tutorial on how to debug invalid JSON in our docs.