### Question:
PersistedCassandraFrameworkConfiguration extends StatePersistedObject<CassandraFrameworkConfiguration> { @NotNull public CassandraFrameworkProtos.RackDc getDefaultRackDc() { CassandraFrameworkProtos.RackDc rackDc = getDefaultConfigRole().getRackDc(); if (rackDc == null) rackDc = CassandraFrameworkProtos.RackDc.newBuilder().setRack("RACK0").setDc("DC0").build(); return rackDc; } PersistedCassandraFrameworkConfiguration(
        @NotNull final State state,
        @NotNull final String frameworkName,
        final long healthCheckIntervalSeconds,
        final long bootstrapGraceTimeSec,
        @NotNull final String cassandraVersion,
        final double cpuCores,
        final long diskMb,
        final long memMb,
        final long javeHeapMb,
        final int executorCount,
        final int seedCount,
        @NotNull final String mesosRole,
        @NotNull final String backupDirectory,
        @NotNull final String dataDirectory,
        final boolean jmxLocal,
        final boolean jmxNoAuthentication,
        @NotNull final String defaultRack,
        @NotNull final String defaultDc,
        @NotNull final List<ExternalDc> externalDcs,
        @NotNull final String clusterName
    ); @NotNull static CassandraFrameworkProtos.CassandraConfigRole.Builder fillConfigRoleGaps(@NotNull final CassandraFrameworkProtos.CassandraConfigRole.Builder configRole); @NotNull Optional<String> frameworkId(); void frameworkId(@NotNull final String frameworkId); @NotNull CassandraFrameworkProtos.CassandraConfigRole getDefaultConfigRole(); @NotNull CassandraFrameworkProtos.RackDc getDefaultRackDc(); @NotNull Duration healthCheckInterval(); void healthCheckInterval(final Duration interval); @NotNull Duration bootstrapGraceTimeSeconds(); void bootstrapGraceTimeSeconds(@NotNull final Duration interval); @NotNull String frameworkName(); @NotNull String clusterName(); @NotNull String mesosRole(); int targetNumberOfNodes(); void targetNumberOfNodes(final int newNodeCount); int targetNumberOfSeeds(); void targetNumberOfSeeds(final int newSeedCount);  }### Answer:
@Test public void testGetDefaultRackDc() { InMemoryState state = new InMemoryState(); PersistedCassandraFrameworkConfiguration config = new PersistedCassandraFrameworkConfiguration( state, "name", 60, 30, "2.1", 0.5, 1024, 1024, 512, 1, 1, "role", "./backup", ".", false, true, "RACK5", "DC5", Lists.<ExternalDc>newArrayList(), "clusterName" ); CassandraFrameworkProtos.RackDc rackDc = config.getDefaultRackDc(); assertEquals("RACK5", rackDc.getRack()); assertEquals("DC5", rackDc.getDc()); CassandraFrameworkConfiguration.Builder builder = CassandraFrameworkConfiguration.newBuilder(config.get()); builder.setDefaultConfigRole(CassandraConfigRole.newBuilder(builder.getDefaultConfigRole()).clearRackDc()); config.setValue(builder.build()); rackDc = config.getDefaultRackDc(); assertEquals("RAC1", rackDc.getRack()); assertEquals("DC1", rackDc.getDc()); }