I think it varies depending on the technology that you are using. Given your case, which is using plain kubernetes. I would use a proxy in between to do the A/B testing. Here is the description:

Before upgrade:
Ingress rule abc.com -> svc-proxy -> pod-proxy --> svc-my-pod (v1.0.0)

After upgrade (A/B) testing:
Ingress rule abc.com -> svc-proxy -> pod-proxy --> svc-my-pod-1 (v1.0.0)
                      |
                      --> svc-my-pod-2 (v1.1.0)

Fully upgraded
Ingress rule abc.com -> svc-proxy -> pod-proxy -> my-pod (v1.1.0)

Note that in the A/B testing phase you would have to add an upstream with weights (if using nginx) to emulate the desired weighted policy.

upstream dynamic {
    server pod-proxy-1      weight=2;
    server pod-proxy-2      weight=4;
}

server {
    location / {
        proxy_pass http://dynamic;
    }
}

Using services and endpoints to switch between pods

Have a yaml with v1 called pod-v1. You would define its match label like the following yaml:

spec:
  selector:
    matchLabels:
      app: pod-v1

Have a yaml with v2 called pod-v2. You would define its match label like the following yaml:

spec:
  selector:
    matchLabels:
      app: pod-v2

Then you can easily change routing between the pods by changing the selector of a service. Like the following yaml:

apiVersion: v1
kind: Service
metadata:
  name: pod
  labels:
    app: pod
spec:
  ports:
  - name: "8000"
    port: 8000
    targetPort: 8000
  selector:
    app: pod-v1
status:
  loadBalancer: {}

Note that to route the traffic to v2 you would just change the selector to match the label pod-v2.

selector:
  app: pod-v2