The "build tree state" holds the state for the entire build definition for a single build execution within a session.

The build tree state is managed by the `BuildTreeState` class.
An instance is created at the start of a build execution and discarded at the end of the execution.

### Build state

The "build state" holds the state for a build within the build definition for a single build execution, and is contained by the build tree state.

* Keep commits discrete. Avoid including multiple unrelated changes in a single commit.
* Keep commits self-contained. Avoid spreading a single change across multiple commits. A single commit should make sense in isolation.

### Testing changes

After making changes, you can test your code in 2 ways:

1. Run tests.

```

These are all Java processes. Each process has a corresponding "runtime".
All source code in Gradle is written to target one or more of these runtimes.
Most source code targets the daemon and the remaining code either targets a single runtime, for example the Gradle client, or is shared across multiple runtimes.

## Composition by architecture modules

Each [architecture module and platform](platforms.md) can contribute code to any of the runtimes.