# Run the test suite and triage the failures in Unreal Engine with Atlas in 2026

> Atlas helps Unreal Engine developers transform overwhelming test output from the Unreal Automation Framework into a clear, prioritized list of distinct root causes for efficient debugging.

Atlas helps Unreal Engine developers in 2026 turn a wall of red test output from the Unreal Automation Framework into a prioritized list of distinct root causes, leveraging its `bash`, `grep`, `todowrite`, and `edit` tools to streamline the debugging process for C++ code.

## Key takeaways

- Atlas uses `bash` to run `Unreal Automation Framework` tests with full log capture.
- Triage Unreal Engine failures by root cause using Atlas's `grep` on complete logs.
- Atlas's `edit` tool helps fix Unreal Engine C++ code, with diff review for safety.
- Atlas understands `UCLASS` macros and `Build.cs` rules for accurate Unreal Engine development.
- All Atlas tool calls are permission-gated, ensuring control over Unreal Engine project changes.

## How to run Unreal Engine Automation Tests with Atlas

In 2026, running your Unreal Engine Automation Tests with Atlas begins by using the `bash` tool to execute the `UnrealEditor-Cmd` command, ensuring a generous timeout of 300000 milliseconds to prevent premature termination of long-running suites. This approach captures the complete output, even for extensive test runs.

Atlas's `bash` tool is essential for executing the `Unreal Automation Framework` tests within your Unreal Engine project. Instead of manually invoking `UnrealEditor-Cmd` with complex arguments, Atlas can run the command directly, such as `UnrealEditor-Cmd.exe MyProject.uproject -run=AutomationTool -test=MyTestSuite -log`. A critical aspect is providing a sufficiently large timeout, for example, `atlas bash --timeout 300000 'UnrealEditor-Cmd.exe MyProject.uproject -run=AutomationTool -test=MyTestSuite -log'`, to accommodate the potentially lengthy execution of a full Unreal Engine test suite. Atlas automatically truncates excessively long terminal output at 2000 lines or 50 KB to maintain terminal responsiveness, but it always writes the complete, untruncated log to a retained file. This ensures that even if the terminal output is a 'wall of red', the full context for triage is preserved and accessible via the path provided in the `...output truncated...` header.

## How to triage Unreal Engine test failures by root cause

To effectively triage Unreal Engine test failures in 2026, Atlas helps you group distinct root causes using its `grep` tool on the complete test log, rather than relying solely on individual test names. This method prevents fixing the same underlying issue multiple times across 10 or more failing tests.

After running the `Unreal Automation Framework` tests, the next step is to analyze the complete log file for distinct root causes. Atlas's `grep` tool is invaluable here. Instead of sifting through hundreds of lines of output in the terminal or manually opening the log file, you can instruct Atlas to `grep` for common failure patterns or error messages within the full log file that was saved. For instance, `atlas grep 'Error: Assertion failed' /path/to/full_log.txt` can quickly identify all occurrences of a specific assertion failure. This approach helps group failures by their underlying problem, rather than just by the test case that exposed them. Once a distinct root cause is identified, Atlas's `todowrite` tool allows you to record it as a pending task, ensuring that each unique issue is tracked and addressed systematically, preventing duplicate effort.

## How Atlas helps fix Unreal Engine code and ensures safety

Atlas assists in fixing Unreal Engine C++ code by leveraging its `edit` tool, allowing you to address issues identified during triage. Before any changes are applied, Atlas computes a unified diff for every file edit and presents it for your approval, ensuring you maintain full control over the 100% of code modifications.

Once distinct root causes are identified and recorded with `todowrite`, Atlas's `edit` tool facilitates fixing the Unreal Engine C++ code. You can instruct Atlas to modify specific files, such as `Source/MyProject/Private/MyActor.cpp`, to address the identified issues. After making a change, you can re-run only the affected `Unreal Automation Framework` tests using the `bash` tool to quickly verify the fix, rather than executing the entire suite. Atlas prioritizes safety and developer control: every proposed file edit, whether to a `.cpp` file or a `Build.cs` module rule, generates a unified diff that is presented for your explicit approval before being written to disk. This allows you to review every line change. Furthermore, Atlas's permission-gated tool calls mean that actions like modifying `Build.cs` to add a module dependency or applying the engine's `.clang-format` style are only executed after your explicit consent, ensuring that Atlas operates within your defined boundaries and adheres to Epic's style guide.

## How Atlas understands the Unreal Engine toolchain

Atlas is specifically designed to understand the Unreal Engine C++ toolchain in 2026, recognizing `UCLASS` macros, the reflection system, and `Build.cs` module rules as core API elements. It builds its code index using AST declarations via tree-sitter, providing a deep, structural understanding of your project's 1000s of lines of code.

Atlas's deep understanding of Unreal Engine C++ projects is fundamental to its effectiveness. It doesn't just treat code as plain text; instead, it builds a robust code index by parsing AST declarations using tree-sitter. This allows Atlas to comprehend the structure and relationships within your `Source/` module folders, including the critical `UCLASS`, `UPROPERTY`, and `UFUNCTION` macros that define Unreal Engine's reflection system. When modifying project dependencies, Atlas knows to first ask to add a module dependency in `Build.cs` (e.g., `PublicDependencyModuleNames.AddRange(new string[] { "MyModule" });`) before attempting to add an `#include` directive, a common pitfall for generic C++ agents. Atlas can also apply the engine's `.clang-format` configuration to ensure code adheres to the Epic style guide. For privacy and security, Atlas can build its code index with local Ollama embeddings, keeping your proprietary Unreal Engine code off third-party servers.

## Steps

1. Run the full `Unreal Automation Framework` test suite using Atlas's `bash` tool, providing a generous timeout like `atlas bash --timeout 300000 'UnrealEditor-Cmd.exe MyProject.uproject -run=AutomationTool -test=All -log'`.
2. If the terminal output was truncated, use Atlas's `read` tool to open the complete test log file, whose path is indicated in the `...output truncated...` header.
3. Group failures by distinct root cause using Atlas's `grep` tool on the complete log file, for example, `atlas grep 'Error: Assertion failed' /path/to/full_log.txt`.
4. Record each distinct root cause as a pending task using Atlas's `todowrite` tool, ensuring all identified issues are tracked.
5. Fix the Unreal Engine C++ code for one root cause at a time using Atlas's `edit` tool, targeting files like `Source/MyProject/Private/MyClass.cpp`.
6. After each fix, re-run only the affected `Unreal Automation Framework` tests via Atlas's `bash` tool to quickly verify the change.
7. Review and approve the unified diff presented by Atlas for every file edit, including changes to `Build.cs` module rules or application of `clang-format`.
8. Repeat steps 5-7 until all distinct root causes are addressed and verified.

## FAQ

### How does Atlas handle large Unreal Engine test logs?

Atlas's `bash` tool truncates terminal output at 2000 lines or 50 KB for responsiveness but always writes the complete `Unreal Automation Framework` log to a retained file, which you can access with the `read` tool for full context.

### Can Atlas help me find the root cause of a specific Unreal Engine crash?

Yes, after running your `Unreal Automation Framework` tests, you can use Atlas's `grep` tool on the complete log file to search for specific crash signatures, error messages, or assertion failures to pinpoint distinct root causes.

### How does Atlas ensure my Unreal Engine code changes are safe?

Atlas computes a unified diff for every proposed file edit, including changes to `Build.cs` or C++ source files, and presents it for your explicit approval before writing to disk. All tool calls are also permission-gated.

### Does Atlas understand Unreal Engine's `Build.cs` files?

Absolutely. Atlas is designed to understand `Build.cs` module rules and will ask to add module dependencies there before adding `#include` directives, correctly handling Unreal Engine's build system.

### Can Atlas apply `clang-format` to my Unreal Engine C++ code?

Yes, Atlas can apply the engine's `.clang-format` configuration to your Unreal Engine C++ code, ensuring it adheres to the Epic style guide, always behind a permission prompt.

### How does Atlas index my Unreal Engine C++ project?

Atlas indexes your Unreal Engine C++ project by parsing AST declarations using tree-sitter, giving it a deep, structural understanding of `UCLASS`, `UPROPERTY`, and `UFUNCTION` macros within your `Source/` module folders.

### Can I use Atlas with my local Ollama models for Unreal Engine development?

Yes, Atlas can build its code index using local Ollama embeddings, ensuring your proprietary Unreal Engine code remains on your local machine and off third-party servers.

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