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.

    assertFalse(fakePool.hasNext());

    // Check that execute can be safely repeated
    e.execute(intCounter);
    e.execute(intCounter);
    e.execute(intCounter);
    // No change yet.
    assertEquals(2, totalCalls.get());
    fakePool.runAll();
    assertEquals(5, totalCalls.get());
    assertFalse(fakePool.hasNext());
  }

  public void testOrdering() {

import org.apache.maven.project.MavenProject;

/**
 * Lifecycle mapping delegate component interface. Calculates project build execution plan given {@link Lifecycle} and
 * lifecycle phase. Standard lifecycles use plugin execution {@code <phase>} or mojo default lifecycle phase to
 * calculate the execution plan, but custom lifecycles can use alternative mapping strategies.
 * <p>

      executor.execute(
          new Runnable() {
            @Override
            public void run() {
              future.set("success");
              if (!future.isDone()) {
                errorMessage.set("Set call exited before future was complete.");
              }
            }
          });
      executor.execute(
          new Runnable() {
            @Override

     * @see org.apache.maven.api.services.SettingsBuilderResult
     * @see org.apache.maven.execution.MavenExecutionRequest
     * @see org.apache.maven.execution.MavenExecutionResult
     * @see org.apache.maven.project.DependencyResolutionRequest
     * @see org.apache.maven.project.DependencyResolutionResult
     * @see org.apache.maven.execution.ExecutionEvent
     * @see org.eclipse.aether.RepositoryEvent
     */

    private org.codehaus.plexus.util.xml.Xpp3Dom configuration;

    /**
     * Describes the source of an execution.
     */
    public enum Source {

        /**
         * An execution that originates from the direct invocation of a goal from the CLI.
         */
        CLI,

        /**
         * An execution that originates from a goal bound to a lifecycle phase.
         */
        LIFECYCLE,
    }

          </params>
        </configuration>
        <executions>
          <execution>
            <id>modello</id>
            <goals>
              <goal>velocity</goal>
              <goal>xdoc</goal>
              <goal>xsd</goal>
            </goals>
            <phase>generate-sources</phase>
          </execution>
        </executions>
      </plugin>
      <plugin>

<plugins>
  <plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-resources-plugin</artifactId>
    <executions>
      <execution>
        <goals>
          <goal>process</goal>
        </goals>
      </execution>
    </executions>
  </plugin>
  .
  .
  .
</plugins>

import org.apache.maven.SimpleLookup;
import org.apache.maven.bridge.MavenRepositorySystem;
import org.apache.maven.execution.DefaultMavenExecutionRequest;
import org.apache.maven.execution.DefaultMavenExecutionResult;
import org.apache.maven.execution.MavenExecutionRequest;
import org.apache.maven.execution.MavenSession;
import org.apache.maven.impl.DefaultRepositoryFactory;
import org.apache.maven.impl.InternalSession;

import java.util.Arrays;
import java.util.List;

import org.apache.maven.execution.AbstractExecutionListener;
import org.apache.maven.execution.DefaultMavenExecutionRequest;
import org.apache.maven.execution.DefaultMavenExecutionResult;
import org.apache.maven.execution.MavenExecutionRequest;
import org.apache.maven.execution.MavenSession;
import org.apache.maven.execution.ProjectDependencyGraph;