Design

Design #

FD.io CSIT system design needs to meet continuously expanding requirements of FD.io projects including VPP, related sub-systems (e.g. plugin applications, DPDK drivers) and FD.io applications (e.g. DPDK applications), as well as growing number of compute platforms running those applications. With CSIT project scope and charter including both FD.io continuous testing AND performance trending/comparisons, those evolving requirements further amplify the need for CSIT framework modularity, flexibility and usability.

Design Hierarchy #

CSIT follows a hierarchical system design with SUTs and DUTs at the bottom level of the hierarchy, presentation level at the top level and a number of functional layers in-between. The current CSIT system design including CSIT framework is depicted in the figure below.

CSIT Design

A brief bottom-up description is provided here:

  1. SUTs, DUTs, TGs

    • SUTs - Systems Under Test;
    • DUTs - Devices Under Test;
    • TGs - Traffic Generators;

  2. Level-1 libraries - Robot and Python

    • Lowest level CSIT libraries abstracting underlying test environment, SUT, DUT and TG specifics;
    • Used commonly across multiple L2 KWs;
    • Performance and functional tests:
      • L1 KWs (KeyWords) are implemented as RF libraries and Python libraries;
    • Performance TG L1 KWs:
      • All L1 KWs are implemented as Python libraries:
        • Support for TRex only today;
        • CSIT IXIA drivers in progress;
    • Performance data plane traffic profiles:
      • TG-specific stream profiles provide full control of:
        • Packet definition - layers, MACs, IPs, ports, combinations thereof e.g. IPs and UDP ports;
        • Stream definitions - different streams can run together, delayed, one after each other;
        • Stream profiles are independent of CSIT framework and can be used in any T-rex setup, can be sent anywhere to repeat tests with exactly the same setup;
        • Easily extensible - one can create a new stream profile that meets tests requirements;
        • Same stream profile can be used for different tests with the same traffic needs;
    • Functional data plane traffic scripts:
      • Scapy specific traffic scripts;

  3. Level-2 libraries - Robot resource files:

    • Higher level CSIT libraries abstracting required functions for executing tests;
    • L2 KWs are classified into the following functional categories:
      • Configuration, test, verification, state report;
      • Suite setup, suite teardown;
      • Test setup, test teardown;

  4. Tests - Robot:

    • Test suites with test cases;
    • Performance tests using physical testbed environment:
      • VPP;
      • DPDK-Testpmd;
      • DPDK-L3Fwd;
      • TRex
    • Tools:
      • CSIT-Dash
      • Testbed environment setup ansible playbooks;
      • Operational debugging scripts;

  5. Test Lifecycle Abstraction

A well coded test must follow a disciplined abstraction of the test lifecycles that includes setup, configuration, test and verification. In addition to improve test execution efficiency, the commmon aspects of test setup and configuration shared across multiple test cases should be done only once. Translating these high-level guidelines into the Robot Framework one arrives to definition of a well coded RF tests for FD.io CSIT. Anatomy of Good Tests for CSIT:

  1. Suite Setup - Suite startup Configuration common to all Test Cases in suite: uses Configuration KWs, Verification KWs, StateReport KWs;
  2. Test Setup - Test startup Configuration common to multiple Test Cases: uses Configuration KWs, StateReport KWs;
  3. Test Case - uses L2 KWs with RF Gherkin style:
    • prefixed with {Given} - Verification of Test setup, reading state: uses Configuration KWs, Verification KWs, StateReport KWs;
    • prefixed with {When} - Test execution: Configuration KWs, Test KWs;
    • prefixed with {Then} - Verification of Test execution, reading state: uses Verification KWs, StateReport KWs;
  4. Test Teardown - post Test teardown with Configuration cleanup and Verification common to multiple Test Cases - uses: Configuration KWs, Verification KWs, StateReport KWs;
  5. Suite Teardown - Suite post-test Configuration cleanup: uses Configuration KWs, Verification KWs, StateReport KWs;

RF Keywords Functional Classification #

CSIT RF KWs are classified into the functional categories matching the test lifecycle events described earlier. All CSIT RF L2 and L1 KWs have been grouped into the following functional categories:

  1. Configuration;
  2. Test;
  3. Verification;
  4. StateReport;
  5. SuiteSetup;
  6. TestSetup;
  7. SuiteTeardown;
  8. TestTeardown;

RF Keywords Naming Guidelines #

Readability counts: “..code is read much more often than it is written.” Hence following a good and consistent grammar practice is important when writing Robot Framework KeyWords and Tests. All CSIT test cases are coded using Gherkin style and include only L2 KWs references. L2 KWs are coded using simple style and include L2 KWs, L1 KWs, and L1 python references. To improve readability, the proposal is to use the same grammar for both Robot Framework KW styles, and to formalize the grammar of English sentences used for naming the Robot Framework KWs. Robot Framework KWs names are short sentences expressing functional description of the command. They must follow English sentence grammar in one of the following forms:

  1. Imperative - verb-object(s): “Do something”, verb in base form.
  2. Declarative - subject-verb-object(s): “Subject does something”, verb in a third-person singular present tense form.
  3. Affirmative - modal_verb-verb-object(s): “Subject should be something”, “Object should exist”, verb in base form.
  4. Negative - modal_verb-Not-verb-object(s): “Subject should not be something”, “Object should not exist”, verb in base form.

Passive form MUST NOT be used. However a usage of past participle as an adjective is okay. See usage examples provided in the Coding guidelines section below. Following sections list applicability of the above grammar forms to different Robot Framework KW categories. Usage examples are provided, both good and bad.

Coding Guidelines #

Coding guidelines can be found on Design optimizations wiki page.