You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: testlib.rs
    path of file: ./repos/nmstate/rust/src/lib/unit_tests
    
    the code of the file until where you have to start completion: // SPDX-License-Identifier: Apache-2.0

use crate::{
    BondConfig, BondInterface, BondMode, EthernetInterface, Interface,
    InterfaceType, Interfaces, LinuxBridgeConfig, LinuxBridgeInterface,
    LinuxBridgePortConfig, MergedInterfaces, OvsBr
    
pub(crate) fn new_nested_4_ifaces() -> [Interface; 6] {
    let br0 = new_br_iface("br0");
    let mut br1 = new_br_iface("br1");
    let mut br2 = new_br_iface("br2");
    let mut br3 = new_br_iface("br3");
    let mut p1 = new_eth_iface("p1");
    let mut p2 = new_eth_iface("p2");

    br1.base_iface_mut().controller = Some("br0".to_string());
    br1.base_iface_mut().controller_type = Some(InterfaceType::LinuxBridge);
    br2.base_iface_mut().controller = Some("br1".to_string());
    br2.base_iface_mut().controller_type = Some(InterfaceType::LinuxBridge);
    br3.base_iface_mut().controller = Some("br2".to_string());
    br3.base_iface_mut().controller_type = Some(InterfaceType::LinuxBridge);
    p1.base_iface_mut().controller = Some("br3".to_string());
    p1.base_iface_mut().controller_type = Some(InterfaceType::LinuxBridge);
    p2.base_iface_mut().controller = Some("br3".to_string());
    p2.base_iface_mut().controller_type = Some(InterfaceType::LinuxBridge);

    // Place the ifaces in mixed order to complex the work
    [br0, br1, br2, br3, p1, p2]
}