Library Guidelines¶

General¶

All users shall prefer to reuse/extending existing libraries over the development of new ones.

Library APIs shall raise python exceptions when errors are encountered, with clear information and stack trace of the reasons of error.

# Wrong
def my_func(var1, var2):
    if ...<some error>:
        return False

# Correct
def my_func(var1, var2):
    if ...<some error>:
        raise Exception('<some error>')

Library APIs shall be designed and implemented to be pythonic: natively object-oriented and returning meaningful objects as opposed to raw strings.
Library APIs shall receive pythonic arguments and parameters.

All CLIs shall be spelled out in full, and never truncated, avoiding ambiguity.

# Wrong
device.execute('sh int')

# Correct
device.execute('show interface')

Libraries should be written using pyATS abstraction package, and always contain the abstract-package declaration in their top-level __init__.py file. With time, token should be added when necessary, following the guidelines outlined in the abstraction package documentation.
Avoid, at all-cost, the writing of local libraries and APIs specific to your script.

Headers¶

Library modules shall contain the following in its docstrings header:
- Owner and support email
- Library version
- Purpose, description and expected results.
Library classes and functions shall contain the following in its docstrings header:
- Purpose, description and expected result
- Input parameter requirement
- Return values
- Possible raised exceptions
Example of docstring in the script templates (eg, pyATS

Configurations¶

Configuration libraries shall take advantage of connection library’s configure() method.
Configuration errors shall be logged as errors. In case of negative testing, such errors shall be logged as debugs.
Libraries that generate configuration shall also generate its anti-configuration (e.g. removal/cleanup)
Configuration functions, classes and methods shall receive all of its inputs via function/class parameters, and global variables shall never be used. Optional configurations shall be enabled/disabled by optional arguments.

Parsers¶

Parsers shall be written using Genie Parsers.
Parser header shall contain an explanation of the resulting parsed dictionary-like structure and all available keys. All keys shall be in lowercase.
Parsers shall be designed to parse as much as possible (parse thoroughly), given a CLI output. Avoid parsing partial information.
Parsers shall support for variants of the same command, such as “| include”, “| exclude”, etc.

Videos [1] [2] on how to develop parser.

Verification¶

Verification APIs shall only use parser outputs, and never parse raw outputs.
Verifications shall only be done using constant polling, and never through a flat wait value. All polling shall have a maximum timeout/retry value. Such timeouts/retries shall be over writable.
Verifications shall break out of the polling loop when desired state is reached (or if errors occurred).
Verifications shall not report errors inside the polling loop. Use debug if necessary. The final result shall only be reported after the polling is complete (or broken out of).
On errors, both the expected value and the retrieved values should be logged for comparisons, as well as a description of the problem statement.
On pass, a confirmation of the expected/retrieve value should be logged.
Verifications should be generic enough that no router configurations are done as part of it. Complex verifications should be done by combining smaller verifications together.

Dialog example¶

# Bad
def send_newline_and_wait_callback(spawn):
    time.sleep(0.5)
    spawn.sendline()

def send_no_and_wait_callback(spawn):
    time.sleep(0.5)
    spawn.sendline("no")

def send_yes_and_wait_callback(spawn):
    time.sleep(0.5)
    spawn.sendline("yes")

def send_multiple_newlines(spawn):
    for _ in range(3):
        time.sleep(2)
        spawn.sendline()
    time.sleep(2)

config_dialog = Dialog([
    Statement(pattern=r"Would you like to enter the "
                      r"initial configuration dialog\?\s\[yes/no\]:\s?$",
                action=send_no_and_wait_callback,
                loop_continue=True),
    Statement(pattern=r"^Would you like to terminate autoinstall\?\s?\[yes\]:\s?$",
                action=send_yes_and_wait_callback,
                loop_continue=True),
    Statement(pattern=r"Press RETURN to get started!",
                action=send_multiple_newlines,
                loop_continue=True),
    Statement(pattern=r'^(.*)>\s?$',
                action=send_newline_and_wait_callback,
                loop_continue=False,
                continue_timer=False)
])

# Good
config_dialog = Dialog([
    Statement(pattern=r"Would you like to enter the initial configuration dialog\?\s\[yes/no\]:\s?$",
            action=sendline(no),
            loop_continue=True,
            continue_timer=0.5),
    Statement(pattern=r"Would you like to terminate autoinstall\?\s\[yes\]:\s?$",
            action=sendline(yes),
            loop_continue=True,
            continue_timer=0.5),
    Statement(pattern=r"Press RETURN to get started!",
            action=sendline(),
            loop_continue=True,
            continue_timer=8),
    Statement(pattern=r"^(.*)>\s?$",
            action=sendline(),
            loop_continue=False)])