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: tests.rs
    path of file: ./repos/svix-webhooks/bridge/svix-bridge/src/config
    
    the code of the file until where you have to start completion: use super::Config;
use crate::config::{LogFormat, LogLevel, SenderConfig};
use std::collections::HashMap;
use svix_bridge_plugin_queue::config::{QueueConsumerConfig, RabbitMqInputOpts, SenderInputOpts};
use svix_bridge_types::{SenderOutputOpts, SvixSenderOutputOpts};

/// This is meant to be a kitchen sink config, hitting as many possible
/// configuration options as possible to en
    
fn test_variable_substitution_available_vars() {
    let src = r#"
    opentelemetry:
        address: "${OTEL_ADDR}"
        sample_ratio: ${OTEL_SAMPLE_RATIO}
    "#;
    let mut vars = HashMap::new();
    vars.insert(
        String::from("OTEL_ADDR"),
        String::from("http://127.0.0.1:8080"),
    );
    vars.insert(String::from("OTEL_SAMPLE_RATIO"), String::from("0.25"));
    let cfg = Config::from_src(src, Some(&vars)).unwrap();
    // when lookups succeed, the token should be replaced.
    let otel = cfg.opentelemetry.unwrap();
    assert_eq!(&otel.address, "http://127.0.0.1:8080");
    assert_eq!(otel.sample_ratio, Some(0.25));
}