To write unit tests for untested Node.js code in 2026, Atlas reads your module, identifies exported symbols, and then generates new test files using `node:test` and `npm` conventions. Atlas ensures these tests run successfully by iterating with you.
How does Atlas identify Node.js code for testing?
Atlas identifies Node.js code for testing by first reading the target module and then using its `lsp` tool to enumerate all exported symbols. This process ensures that in 2026, no public function or class within your Node.js module is missed when generating new unit tests.
Atlas begins the unit testing workflow by thoroughly understanding the Node.js module you intend to test. It uses the `read` tool to ingest the module's source code. Following this, Atlas employs the `lsp` tool with its `documentSymbol` operation. This operation leverages Atlas's AST declarations indexing, built with tree-sitter, to precisely identify and list every exported symbol within the Node.js file. This detailed enumeration is crucial for ensuring comprehensive test coverage, as it guarantees that Atlas will draft tests for every public interface exposed by your module, adhering to the principle of testing all public APIs. This capability is fundamental for Node.js developers aiming for robust test suites without manual symbol identification.
How does Atlas match existing Node.js test conventions?
Atlas matches existing Node.js test conventions by using the `grep` tool to find an existing test file, then copying its framework, import style, and naming convention. This ensures that new `node:test` files integrate direct into your 2026 Node.js project.
To ensure new unit tests align perfectly with your existing Node.js codebase, Atlas first uses the `grep` tool. It searches your repository for an existing test file, which serves as a template for the new tests. This step is vital because it allows Atlas to learn and replicate your project's specific testing framework, such as how `node:test` is imported and used, the preferred import style for modules under test, and the established naming conventions for test files and test cases. By mirroring these conventions, Atlas ensures that the newly generated test files, often named `*.test.js` or `*.spec.js`, feel native to your project, reducing friction and maintaining consistency across your Node.js services. This approach prevents Atlas from inventing new conventions, instead adapting to your team's established practices.
How does Atlas write and run Node.js unit tests?
Atlas writes new Node.js unit test files using the `write` tool, which presents a unified diff for approval, then runs the suite with the `bash` tool. This ensures that in 2026, every generated `node:test` actually executes and passes.
After identifying the module's symbols and understanding the repository's test conventions, Atlas proceeds to write the new Node.js unit test file. It uses the `write` tool for this purpose. Before any changes are committed to disk, Atlas computes a unified diff for the proposed file edit and surfaces it for your approval, providing a critical safety check. Once approved, the new test file, typically using `node:test` syntax, is created. The crucial next step is execution: Atlas uses the `bash` tool to run the entire test suite, often via an `npm test` script that invokes `node --test`. This immediate execution is paramount because a test that was never executed is not a test. Atlas reads the test failures, and if the output exceeds 2000 lines or 50 KB, it truncates the display but saves the full log to a file for your review. This iterative process of writing and running allows Atlas to refine the tests until they are green, ensuring functional and validated unit tests for your Node.js application.
How does Atlas ensure safety and review for Node.js test changes?
Atlas ensures safety and review for Node.js test changes by presenting a unified diff for every file edit and requiring explicit approval before writing. This permission-gated approach means you control all changes to your `package.json` or test files in 2026.
Atlas integrates several layers of safety and review into its workflow for writing Node.js unit tests. Every Atlas tool call is permission-gated against allow, ask, and deny rules, giving you granular control. Specifically, when Atlas proposes to `write` a new test file or modify an existing one, it first drafts a plan in a read-only plan agent and asks for your confirmation before switching to a build agent. Crucially, Atlas computes a unified diff for every file edit and surfaces it for your approval before writing anything to disk. This means you always see exactly what changes Atlas intends to make to your Node.js project, whether it's a new `*.test.js` file or an update to `package.json` scripts. Atlas also snapshots file changes as git patches, allowing edits to be easily diffed and rolled back if needed. This transparent and approval-based system ensures that you, the Node.js developer, maintain full control and oversight over all code modifications.
Step by step
- 011: Read the Node.js module: Use Atlas to `read` the target Node.js module, for example, `src/utils/math.js`. Atlas will then use the `lsp` tool's `documentSymbol` operation to enumerate all exported functions and classes, ensuring comprehensive test coverage.
- 022: Identify Node.js test conventions: Instruct Atlas to `grep` your repository for an existing `*.test.js` or `*.spec.js` file. This step allows Atlas to learn your project's specific `node:test` framework, import style, and naming conventions, ensuring consistency.
- 033: Write the new Node.js spec file: Use the Atlas `write` tool to generate the new unit test file, for instance, `test/utils/math.test.js`. Atlas will present a unified diff for your review and approval before writing the file to disk, using the learned `node:test` conventions.
- 044: Run the Node.js test suite: Execute the newly written tests and the rest of your suite using the Atlas `bash` tool, typically with `npm test` or `node --test`. Atlas will capture the output, truncating large logs but saving the full details to a file for review.
- 055: Iterate and refine Node.js tests: If tests fail, use the Atlas `edit` tool to make necessary adjustments to the test file or the module under test. For large modules, use `todowrite` to manage progress, ensuring all `node:test` cases eventually pass.
- 066: Stage and commit Node.js changes: Once all tests are green, use Atlas to `git add` and `git commit` the new test files and any related changes, leveraging Atlas's ability to read git branches, status, and diffs.
Frequently asked questions
- How does Atlas ensure new Node.js tests match my existing project style?
- Atlas uses the `grep` tool to find an existing `*.test.js` file in your Node.js project. It then analyzes this file to understand and replicate your specific `node:test` framework, import style, and naming conventions for new test files.
- Can Atlas run `npm test` for my Node.js project?
- Yes, Atlas can run `npm test` or any other shell command using its `bash` tool. This allows it to execute your Node.js test suite, capture output, and help you iterate on failures.
- What Node.js test runner does Atlas support?
- Atlas is designed to work direct with the standard Node.js test runner, `node:test`. It understands its syntax and conventions to generate and execute tests effectively.
- How does Atlas prevent accidental changes to my Node.js codebase?
- Atlas implements a permission-gated system. Every proposed file edit, including new Node.js test files, generates a unified diff that requires your explicit approval before Atlas writes anything to disk.
- Does Atlas keep my Node.js code private when generating tests?
- Yes, Atlas can build its code index with local Ollama embeddings, keeping your Node.js code off third-party servers. This ensures your proprietary code remains private during the test generation process.
- How does Atlas handle large Node.js test output?
- When running Node.js tests, Atlas truncates output exceeding 2000 lines or 50 KB in the terminal. However, it saves the full log to a file that you can access and review for detailed debugging.
- Can Atlas help me refactor my Node.js tests after they are written?
- While the primary job is writing new tests, Atlas's `edit` tool allows you to modify existing files. You can use it to refine or refactor your `node:test` files, iterating until they meet your standards.
Try Atlas in your terminal
The terminal-native AI coding agent. Free core, single binary.
Install AtlasRelated guides
Write Unit Tests for Untested Code with Atlas in 2026
How to write unit tests for untested code with Atlas in 2026: the lsp tool enumerates exported symbols, grep copies repo conventions, and bash actually runs the suite.
Atlas for Node.js in 2026
Node.js developers in 2026 can adopt Atlas, the terminal-native AI coding agent, for secure, efficient development. Leverage local embeddings, AST indexing, and robust safety features.
Plan a Multi-File Node.js Change Before Editing with Atlas (2026)
Design a multi-file Node.js change before a line is edited: Atlas plan mode denies all edit tools in 2026, writes the plan, then asks before switching to build.
Debug a Single Failing Test in Node.js with Atlas in 2026
Pinpoint and fix failing Node.js tests with Atlas in 2026. Learn how Atlas uses `node:test` and `npm` to isolate issues, walk call graphs, and apply precise code fixes.
Review a pull request in Node.js with Atlas in 2026
In 2026, Node.js developers use Atlas to review pull requests, leveraging its AI to fetch diffs, analyze code context, run `node:test` suites, and ensure code quality with `npm` and `prettier`.
Run Node.js Test Suites and Triage Failures with Atlas in 2026
Streamline Node.js test triage in 2026 with Atlas. Turn walls of `node:test` output into prioritized fixes, leveraging `npm` for efficient debugging and tracking.
Automate GitHub Issue and Pull Request Triage in Node.js with Atlas in 2026
Automate GitHub issue and pull request triage for your Node.js projects using Atlas in 2026. Configure Atlas within GitHub Actions to safely respond to events, ensuring only trusted users trigger AI-driven responses for
Onboard to an Unfamiliar Node.js Codebase With Atlas (2026)
Build a mental model of a Node.js repo without reading every file. Atlas maps package.json, npm scripts, and Express routes with codebase_search, glob, and the explore subagent.