@Test
  public void createWithSystem_doesNotSetSystemCache_onGivenSystem__ifSystemCacheIsOpen_butExistingNotOk() {
    InternalCache openCache = cache(OPEN);
    InternalDistributedSystem givenSystem = systemWith(openCache);

    InternalCacheBuilder internalCacheBuilder = new InternalCacheBuilder(
        new Properties(), new CacheConfig(), metricsSessionBuilder, THROWING_SYSTEM_SUPPLIER,
        THROWING_SYSTEM_CONSTRUCTOR,
        THROWING_CACHE_SUPPLIER, THROWING_CACHE_CONSTRUCTOR);

    ignoreThrowable(() -> internalCacheBuilder
        .setIsExistingOk(false)
        .create(givenSystem));

    verify(givenSystem, never()).setCache(any());
  }
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