yang¶

YANG, “Yet Another Network Generation”, is a data modeling language used to model configuration and state data on network devices. The model is represented in a hierachal fashion and can be presented in many ways, one of which is the “Xpath”. The content of a simple YANG message can be boiled down to 3 required components.

Xpath based on XML Path Language 1.0 identifying a resource

Namespaces in XML 1.0

The value you wish to set the resource to

Several Xpath/value pairs can construct a complex message. This is the format the yang action follows when defining simple or complex messages.

Description of Available YAML Components¶

- yang:
    device: # device name or alias
    connection: # device interface connection (in testbed file)
    operation:  # YANG message operation (based on NETCONF but mapped to other protocols)
                # * edit-config - mapped to "set" for gNMI
                # * get-config  - mapped to "get CONFIG mode" for gNMI
                # * get         - mapped to "get STATE mode" for gNMI
                # * subscribe
                # * capabilities
    protocol: # [ netconf | gnmi ]
    datastore: # YANG datastores (if not defined MPTE will choose from device capabilities)
    format: # Various fomat options (see Format options below)
    banner: # (optional) Prominant log message with borders
    log: # (optional) Log INFO message
    content: # Content of YANG message being sent (see Content section below)
    returns: # (optional) Expected return of YANG message (see Returns section below)

Format Options¶

Some format options are available relating to the message and return handling. For example, if the message is related to a subscribe operation, you will need to communicate the type of subscription, or, you may expect the test to fail (referred to as a negative test).

format:
  request_mode:    # [STREAM, ONCE, POLL]
  sub_mode:        # [ON_CHANGE, SAMPLE]
  encoding:        # [JSON, JSON_IETF]
  sample_interval: # seconds (default)
  stream_max: 20   # seconds to stop stream (default no max)
  auto-validate:   # [true | false] automatically validate config messages
  negative-test:   # [true | false] expecting device to return an error
  delay: 0         # pause N seconds between each test (global ``sleep``)

Content¶

As explained above, content contains a reference to namespaces followed by a list of Xpath/value pairs (nodes). Namespace with mapped prefix is defined at the top of the YANG file.

content:
  namespace:
    # prefix: namespace examples:
    ios: http://cisco.com/ns/Cisco-IOS-XE-native
    config-mda-cfg: http://cisco.com/ns/yang/Cisco-IOS-XR-config-mda-cfg
    oc-if: http://openconfig.net/yang/interfaces
  nodes: # List of:
  - xpath: # Xpath based on `XML Path Language 1.0`_ identifying a resource
    value: # Value Xpath points to which must match the defined datatype
    edit-op: # (Optional) Applies only to edit-config
             # [ create | merge | replace | delete | remove ]

Returns¶

Expected return values can also be defined with the fexibility of approximation. The return values are identified by the Xpath derived from the return message (without prefixes because return prefixes may differ). The op is an operation performed between returned value and expected value.

== equals

!= not equal

< less than

> greater than

<= less than or equal

>= greater than or equal

1 - 10 range (example)

returns:
  - id:       # for referencing only
    name:     # name of field for referencing only
    op:       # operation performed between returned value and expected value (choices above)
    selected: # set this to ``false`` and field is ignored making it like a placeholder
    datatype: # datatype of field for general verification
    value:    # expected value to compare to returned value
    xpath:    # Xpath to field in YANG model (without prefixes)

Using Variables¶

You should think about the portability of your test. Using variables to refer to parameters in the yang action will allow you to run the same set of tests over different protocols by only changing a couple variables or changing the file that contains your content. A variable can be defined by wrapping a YAML location inside %{ my.variable } and find the value at “my: variable: value”. The location can also exist in a different file by adding extends: mydata.yml at the top of the test file.

Example of variables in external data file:

extends: data_test_file.yml

- yang:
    device: '%{ data.device }'
    connection: '%{ data.connection }'
    operation: edit-config
    protocol: '%{ data.protocol }'
    datastore: '%{ data.datastore }'
    banner: YANG EDIT-CONFIG MESSAGE
    content: '%{ data.content.1 }'

Content in data_test_file.yml:

data:
  device: uut1
  connection: gnmi
  protocol: gnmi
  content:
    1:
      namespace:
        ios-l2vpn: http://cisco.com/ns/yang/Cisco-IOS-XE-l2vpn
      nodes:
        - value: 10.10.10.2
          xpath: /native/l2vpn-config/ios-l2vpn:l2vpn/ios-l2vpn:router-id
          edit-op: merge

Examples¶

edit-config negative test using NETCONF

- yang:
    device: uut2
    connection: netconf
    operation: get-config
    protocol: netconf
    banner: NETCONF EDIT-CONFIG MESSAGE
    log: Negative test case
    format:
      auto-validate: false
      negative-test: true
    content:
      namespace:
        ios-l2vpn: http://cisco.com/ns/yang/Cisco-IOS-XE-l2vpn
      nodes:
      - xpath: /native/l2vpn-config/ios-l2vpn:l2vpn/ios-l2vpn:router-id
        value: '10.10.10.2'
        edit-op: delete
    returns:
      - id: 2
        name: router-id
        op: ==
        selected: true
        datatype: string
        value: 10.10.10.2
        xpath: /native/l2vpn-config/l2vpn/router-id

Same edit-config using variables

extends: data_test_file.yml

  - yang:
      device: '%{ data.device }'
      connection: '%{ data.connection }'
      operation: edit-config
      protocol: '%{ data.protocol }'
      datastore: '%{ data.datastore }'
      format: '%{ data.format.1 }'
      banner: YANG EDIT-CONFIG MESSAGE
      content: '%{ data.contents.1 }'
      banner: NETCONF EDIT-CONFIG MESSAGE
      log: Negative test case

# data_test_file.yml contents

data:
  device: uut2
  connection: netconf
  protocol:netconf
  datastore: candidate

  format:
    1:
      auto-validate: false
      negative-test: true
  contents:
    1:
      namespace:
          ios-l2vpn: http://cisco.com/ns/yang/Cisco-IOS-XE-l2vpn
      nodes:
      - xpath: /native/l2vpn-config/ios-l2vpn:l2vpn/ios-l2vpn:router-id
          value: '10.10.10.2'
          edit-op: delete
  returns:
    1:
      - id: 2
          name: router-id
          op: ==
          selected: true
          datatype: string
          value: 10.10.10.2
          xpath: /native/l2vpn-config/l2vpn/router-id

get CONFIG state using gNMI with expected returns

- yang:
    device: uut2
    connection: gnmi
    operation: get-config
    protocol: gnmi
    banner: gNMI GET-CONFIG MESSAGE
    content:
      namespace:
        ios-l2vpn: http://cisco.com/ns/yang/Cisco-IOS-XE-l2vpn
      nodes:
      - xpath: /native/l2vpn-config/ios-l2vpn:l2vpn/ios-l2vpn:router-id
    returns:
      - id: 2
        name: router-id
        op: ==
        selected: true
        datatype: string
        value: 10.10.10.2
        xpath: /native/l2vpn-config/l2vpn/router-id

gNMI subscribe testing a config change

- configure:
    commmand:
      - l2vpn router-id 10.10.10.1
- sleep:
    sleep_time: 5
- yang:
    device: uut2
    connection: gnmi
    operation: subscribe
    protocol: gnmi
    banner: gNMI SUBCRIBE MESSAGE
    format:
      request_mode: STREAM
      sub_mode: SAMPLE
      encoding: JSON_IETF
      sample_interval: 5
      stream_max: 20       # test completes after 20 seconds
    content:
      namespace:
        ios-l2vpn: http://cisco.com/ns/yang/Cisco-IOS-XE-l2vpn
      nodes:
      - xpath: /native/l2vpn-config/ios-l2vpn:l2vpn/ios-l2vpn:router-id
    returns:
      - id: 2
        name: router-id
        op: ==
        selected: true
        datatype: string
        value: 10.10.10.2
        xpath: /native/l2vpn-config/l2vpn/router-id
- sleep:
    sleep_time: 5
# following event will trigger a returns check
- configure:
    commmand:
      - l2vpn router-id 10.10.10.2