renovate-test-target/renovate.json

{
  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
  "regexManagers": [
    {
      "fileMatch": [
        "^host_test\\.yml$",
        "^host_vars/test/vars\\.yml$"
      ],
      "datasourceTemplate": "docker",
      "versioningTemplate": "docker",
      "matchStrings": [
        "image: (?<depName>[-{]*?):(?<currentValue>.*?)(@sha256:(?<currentDigest>.*?))?\\s"
      ]
    }
  ]
}