Your browser does not support JavaScript! Skip to main content
Free 30-day trial Customer portal Contact
 
Rapita Systems
 

Industry leading verification tools & services

Rapita Verification Suite (RVS)

  RapiTest - Unit/system testing   RapiCover - Structural coverage analysis   RapiTime - Timing analysis (inc. WCET)   RapiTask - Scheduling visualization   RapiCoverZero - Zero footprint coverage analysis   RapiTimeZero - Zero footprint timing analysis   RapiTaskZero - Zero footprint scheduling analysis

Multicore verification

  CAST-32A Compliance   Multicore Timing Solution   RapiDaemons

Services

  V & V Services   Qualification   Training   Tool Integration

Industries

  Aerospace (DO-178C)   Automotive (ISO 26262)   Space

Other

  RTBx   Mx-Suite   Software licensing   Product life cycle policy

Latest from Rapita HQ

Latest news

Propelling the next generation of scientists
DO-178C Virtual Training - November 2020
NXP MCFA 2020

Latest from the Rapita blog

Leveraging FACE Conformance Artifacts to Support Airworthiness
Assured Multicore Partitioning for FACE Systems
Going above and beyond the quality standards

Upcoming events

Safe Use of Multi-Core Processors Seminar
2021-04-05

Technical resources for industry professionals

Latest White Papers

Multicore Timing Analysis for DO-178C
Seven Roadblocks to 100% Structural Coverage (and how to avoid them)
Eight top code coverage questions in embedded avionics systems

Latest Videos

MASTECS Project
Testing using the RapiTest scripting language thumbnail
Testing using the RapiTest scripting language
Continuous verification with RVS and Jenkins Thumbnail
Continuous verification with RVS and Jenkins
Zero footprint timing analysis with RapiTime Zero Thumbnail
Zero footprint timing analysis with RapiTime Zero
RapiTask Zero Thumbnail
Zero-footprint system event tracing with RapiTask Zero

Latest Webinars

Incremental Assurance of Multicore Integrated Modular Avionics (IMA)
Certifying multicore systems for DO-178C (CAST-32A) projects
Airborne Safety with FACE™ in the Digital Battlespace

Latest Case studies

Cobham Aerospace Connectivity: RapiCover continues to deliver on the most challenging targets
DO-178B Level A Embraer FCS
Validation of COTS Ada Compiler for Safety-Critical Applications

Discover Rapita

Who we are

The company menu

  • About us
  • Customers
  • Distributors
  • Locations
  • Partners
  • Research projects
  • Contact us

Careers

Careers menu

  • Current opportunities & application process
  • Working at Rapita

US office

+1 248-957-9801
info@rapitasystems.com
41131 Vincenti Ct.
Novi, MI, 48375
USA

UK office

+44 (0)1904 413945
enquiries@rapitasystems.com
Atlas House
York, YO10 3JB
UK

Back to Top

CAST-10 "Literal" Interpretation of Decision Coverage Increases Rigor of Testing Requirements

Breadcrumb

  1. Home
  2. Blog
  3. CAST 10 "Literal" Interpretation of Decision Coverage Increases Rigor of Testing Requirements
2015-03-25

The Certification Authorities Software Team (CAST) issue guidance on various issues regarding the interpretation of DO-178B and DO-178C. In the CAST-10 position paper [1], they discuss the interpretation of a "decision".

In CAST-10, three possible interpretations are made for a decision:

  • The "literal" interpretation of DO-178B, namely a Boolean expression composed of conditions and zero or more Boolean operators.
  • The "relaxed" interpretation of DO-178B, namely a decision is equivalent to a branch.
  • An intermediate position, where the literal interpretation applies to MC/DC, and the relaxed interpretation applies to Branch Coverage.

CAST-10 illustrates this with an example:

A := B or C;
E := A and D;
if E then …

So in the case of decision coverage, the tests required are:

  Literal Relaxed
Test cases where: A is assigned true
A is assigned false
E is assigned true
E is assigned false
E has the correct effect on the if-statement








E has the correct effect on the if-statement

What impact does the interpretation of this decision have on tests?

In a recent project we compared the impact of the two interpretations, and found that where the relaxed interpretation required tests to cover approximately 18,500 decisions, the literal interpretation identified nearly 2,400 additional decisions that required testing (11.4% more).

For DO-178B/DO-178C level B software, the interpretation of what constitutes a decision will need to be carefully considered: this variation could result in a considerable increase in the amount of testing required, but it could also result in a considerable improvement to the overall integrity of the final application.

Naturally, we would recommend that you ensure that your coverage tool supports both interpretations to provide maximum flexibility.

[1] CAST 10 – What is a “Decision” in Application of Modified Condition/Decision Coverage (MC/DC) and Decision Coverage (DC)? June 2002. https://www.faa.gov/aircraft/air_cert/design_approvals/air_software/cast/cast_papers/media/cast-10.pdf

White papers

  • Solutions
    • Rapita Verification Suite
    • RapiTest
    • RapiCover
    • RapiTime
    • RapiTask

    • CAST-32A Compliance Package
    • Verification and Validation Services
    • Qualification
    • Training
    • Integration
  • Latest
  • Latest menu

    • News
    • Blog
    • Events
    • Videos
  • Downloads
  • Downloads menu

    • Brochures
    • Webinars
    • White Papers
    • Case Studies
    • Product briefs
    • Technical notes
    • Software licensing
  • Company
  • Company menu

    • About Rapita
    • Customers
    • Distributors
    • Industries
    • Locations
    • Partners
    • Research projects
    • Contact
  • Discover
    • AMC 20-193
    • What is CAST-32A?
    • Multicore Timing Analysis

    • MC/DC Coverage
    • Code coverage for Ada, C & C++
    • Embedded Software Testing Tools
    • Aerospace Software Testing
    • Automotive Software Testing
    • Certifying eVTOL
    • DO-178C Testing

    • WCET Tools
    • Worst Case Execution Time

All materials © Rapita Systems Ltd. 2021 - All rights reserved | Privacy information Subscribe to our newsletter