def METHOD_NAME():
    elb_template = {
        "AWSTemplateFormatVersion": "2010-09-09",
        "Resources": {
            "MyELB": {
                "Type": "AWS::ElasticLoadBalancing::LoadBalancer",
                "Properties": {
                    "LoadBalancerName": "test-elb",
                    "AvailabilityZones": ["us-west-1a"],
                    "Listeners": [
                        {
                            "InstancePort": "80",
                            "LoadBalancerPort": "80",
                            "Protocol": "HTTP",
                        }
                    ],
                    "Policies": {"Ref": "AWS::NoValue"},
                },
            }
        },
    }
    elb_template_json = json.dumps(elb_template)
    # when
    cf = boto3.client("cloudformation", region_name="us-west-1")
    cf.create_stack(StackName="elb_stack", TemplateBody=elb_template_json)
    # then
    elb = boto3.client("elb", region_name="us-west-1")
    load_balancer = elb.describe_load_balancers()["LoadBalancerDescriptions"][0]
    assert load_balancer["AvailabilityZones"] == ["us-west-1a"]
    # when
    elb_template["Resources"]["MyELB"]["Properties"]["AvailabilityZones"] = [
        "us-west-1b"
    ]
    elb_template_json = json.dumps(elb_template)
    cf.update_stack(StackName="elb_stack", TemplateBody=elb_template_json)
    # then
    load_balancer = elb.describe_load_balancers()["LoadBalancerDescriptions"][0]
    assert load_balancer["AvailabilityZones"] == ["us-west-1b"]