Add section on building and testing from source to README and CLA agreement

CONTRIBUTING.md

@@ -67,6 +67,153 @@ To run the link-checker, follow these steps:
   `npm install -g markdown-link-check@3.8.5`
 * run `find . \*.md -exec markdown-link-check {} \;`
 
+## Contributing to Code
+
+### Contributor License Agreement (CLA)
+
+Contributions to the DSC repository requires signing the [Contributor License Agreement (CLA)][01].
+You can manually sign the CLA at any time. When you submit a pull request to this repository, the
+continuous integration will check whether you have already signed the CLA. If you haven't, the
+automation will prompt you to do so as a comment on your PR.
+
+We can't accept any contributions without the author signing the CLA. Signing the CLA is a one-time
+requirement and applies to contributions to Microsoft open source repositories.
+
+For more information, see [Contributor License Agreements][01].
+
+[01]: https://cla.microsoft.com/
+
+### Building and testing
+
+#### Prerequisites
+
+Building the DSC project requires PowerShell 7.2 or later to execute the build script. For more
+information about installing PowerShell, see [Install PowerShell on Windows, Linux, and macOS][02].
+
+DSC requires other tools for building the project. The build script (`build.new.ps1`) installs the
+tools in the following table if they aren't already installed on your system:
+
+| Tool                                                    |    Version    |       Platforms       | Projects                                             |
+|:--------------------------------------------------------|:-------------:|:---------------------:|:-----------------------------------------------------|
+| [Rust toolchain][03]                                    | Latest stable | Linux, macOS, Windows | All Rust crates                                      |
+| [Visual Studio Build Tools for C++][04]                 | Latest stable |        Windows        | All Rust crates                                      |
+| [`cargo audit`][05]                                     | Latest stable | Linux, macOS, Windows | All Rust crates                                      |
+| [Clippy][06]                                            | Latest stable | Linux, macOS, Windows | All Rust crates                                      |
+| [Tree-sitter CLI][07]                                   | Latest stable | Linux, macOS, Windows | All grammars                                         |
+| [NodeJS][08]                                            |     `v24`     | Linux, macOS, Windows | All grammars                                         |
+| [**Pester** PowerShell module][09]                      | Latest stable | Linux, macOS, Windows | All acceptance tests                                 |
+| [**PSDesiredStateConfiguration** PowerShell module][10] |   `v2.0.7`    |        Windows        | `Microsoft.Windows/WindowsPowerShell` adapter  tests |
+
+[02]: https://learn.microsoft.com/powershell/scripting/install/installing-powershell
+[03]: https://rustup.rs/
+[04]: https://learn.microsoft.com/cpp/windows/latest-supported-vc-redist
+[05]: https://crates.io/crates/cargo-audit
+[06]: https://doc.rust-lang.org/clippy/index.html
+[07]: https://github.com/tree-sitter/tree-sitter/blob/master/crates/cli/README.md
+[08]: https://nodejs.org/
+[09]: https://pester.dev/
+[10]: https://www.powershellgallery.com/packages/PSDesiredStateConfiguration/2.0.7
+
+#### Quick start
+
+```powershell
+# Build the project
+./build.new.ps1
+
+# Build with linting (recommended)
+./build.new.ps1 -Clippy
+
+# Build and run all tests
+./build.new.ps1 -Clippy -Test
+
+# Build in release mode (optimized)
+./build.new.ps1 -Release
+```
+
+#### Running tests
+
+DSCv3 includes Rust unit tests and PowerShell Pester tests:
+
+```powershell
+# Run all tests
+./build.new.ps1 -Test
+
+# Run only Rust tests
+./build.new.ps1 -Test -ExcludePesterTests
+
+# Run only Pester tests
+./build.new.ps1 -Test -ExcludeRustTests
+
+# Run specific Pester test groups
+./build.new.ps1 -SkipBuild -Test -ExcludeRustTests -PesterTestGroup dsc
+```
+
+Available Pester test groups include:
+
+- `dsc` - Acceptance tests for the `dsc` executable.
+- `adapters` - Acceptance tests for projects in the `adapters` folder.
+- `extensions` - Acceptance tests for projects in the `extensions` folder.
+- `resources` - Acceptance tests for projects in the `resources` folder.
+- `grammars` - Acceptance tests for projects in the `grammars` folder.
+
+#### Cross-platform builds
+
+By default, the build script compiles code for the current platform and architecture. You can build
+for other platforms and architectures with the `-Architecture` parameter:
+
+```powershell
+# Windows ARM
+./build.new.ps1 -Architecture aarch64-pc-windows-msvc
+
+# macOS Apple Silicon
+./build.new.ps1 -Architecture aarch64-apple-darwin
+
+# Linux x64
+./build.new.ps1 -Architecture x86_64-unknown-linux-gnu
+```
+
+#### Additional Information
+
+For detailed build instructions, troubleshooting, and CI/CD workflows, see the
+[Build and Test Instructions](.github/instructions/instructions.md).
+
+### Pull Request Guidelines
+
+- Always create a pull request to the `main` branch of this repository.
+- Avoid making big pull requests. Before you invest a large amount of time, file an issue and start
+  a discussion with the community.
+- Add a meaningful title to the PR describing what change you want to check in.
+- When you create a pull request, include a summary about your changes in the PR description. If
+  the changes are related to an existing GitHub issue, please reference the issue in the PR
+  description (e.g. `Fix #123`).
+- Please use the present tense and imperative mood when describing your changes:
+
+  - Instead of `Adding support for new feature`, write `Add support for new feature`.
+  - Instead of `Fixed bug in parser`, write `Fix bug in parser`.
+
+- If your change adds a new source file, ensure the appropriate copyright and license headers are
+  included at the top of the file:
+
+  - For `.rs` files, use the copyright header with an empty line after it:
+
+    ```rust
+    // Copyright (c) Microsoft Corporation.
+    // Licensed under the MIT License.
+
+    ```
+
+  - For `.ps1` and `.psm1` files, use the copyright header with an empty line after it:
+
+    ```powershell
+    # Copyright (c) Microsoft Corporation.
+    # Licensed under the MIT License.
+
+    ```
+
+* Create and update relevant tests when making code changes.
+* Run tests and ensure they're passing before opening a pull request.
+* All pull requests **must** pass CI checks before they can be merged.
+
 ## Code of Conduct Enforcement
 
 Reports of abuse will be reviewed by the PS-Committee and if it has been determined that violations of the

README.md

@@ -42,6 +42,8 @@ To install DSC v3:
 1. Expand the release archive.
 1. Add the folder containing the expanded archive contents to the `PATH`.
 
+For information on building and testing DSC from source, see the [Contributing Guide](CONTRIBUTING.md).
+
 ## Explore DSCv3
 
 If you're new to DSC or configuration management, we recommend reviewing the [documentation][02].