public String getPlugin() {
        return plugin;
    }
@Test
    public void thePluginCanBeChanged() {

        doReturn(pluginManager).when(xmppServer).getPluginManager();

        final SystemProperty<Long> longProperty = SystemProperty.Builder.ofType(Long.class)
            .setKey("a-plugin-property")
            .setDefaultValue(42L)
            .setPlugin("TestPluginName")
            .setDynamic(false)
            .build();

        assertThat(longProperty.getPlugin(), is("TestPluginName"));
    }