@Before
  public void setUp() {
    initMocks(this);

    System.setProperty(ALLOW_MULTIPLE_SYSTEMS_PROPERTY, "true");
  }
Unit tests for {@link InternalCacheBuilder} when
{@code InternalDistributedSystem.ALLOW_MULTIPLE_SYSTEMS} is set to true.
geode-core/src/test/java/org/apache/geode/internal/cache/InternalCacheBuilderAllowsMultipleSystemsTest.java