In defense programs, an electronic system is not considered validated simply because it works, but only when it can be demonstrated that it meets each of its specific requirements. This distinction shifts the focus from testing to methodology: test benches designed based on requirements, repeatable procedures, and objective evidence archived in a retrievable manner are essential. This article describes how to build a traceable validation chain—from the requirement to the test result—and which engineering choices make it reliable.
The Operational Context
In the defense sector, the validation of electronic systems takes place within a framework of formal requirements, defined by the customer and verified throughout the entire supply chain. Traceable validation refers to the process by which each system requirement is linked to one or more tests, and each test to objective evidence documenting its outcome, so that compliance can be demonstrated rather than merely declared.
In this context, the test bench is the operational tool for validation. A test bench refers to the combination of hardware, measurement instrumentation, and control software that reproduces controlled operating conditions to verify the behavior of a system under test. The quality of validation depends on the quality of the test bench and the method by which it is designed and used.
The reference scenario is defined by four elements:
- stringent technical requirements, specified by the customer and subject to formal verification;
- heterogeneous systems under test, combining analog and digital electronics and interfaces to other subsystems;
- security and confidentiality constraints regarding data exchanged during testing;
- audits and certifications that require documentation that is accessible and consistent over time.
The Technical Challenge
The main difficulty is not performing the tests, but demonstrating that the set of tests covers all requirements and that each result is documented in a verifiable manner. This demonstration requires addressing several critical issues simultaneously.
There are five recurring critical issues:
- Requirement Coverage: Every functional and performance requirement must have at least one associated test; otherwise, compliance remains unproven.
- System Heterogeneity: A test bench designed for a single configuration requires redesign every time the system under test changes.
- Objective Evidence: Measurements, logs, and records must be collected according to uniform criteria and linked to the requirement to which they refer.
- Repeatability: A test performed manually, with parameters that vary from one operator to another, produces results that are difficult to compare.
- Security constraints: Tests must comply with the confidentiality requirements and operational conditions specified by the program.
Unstructured approaches expose the program to a specific risk. When tests are defined after development is complete, or when evidence is archived without reference to requirements, nonconformities emerge in later phases, where correcting them requires more time and resources. Automated functional verification reduces this risk, but it has a limitation: not all tests can be automated, and those requiring human intervention must be designed in conjunction with the rest of the process.
The Correct Approach
The engineering approach to traceable validation starts with the requirements and leads to test results through documented steps. Each step produces a verifiable artifact, and the link between these artifacts constitutes traceability.
The first step is requirements analysis: each requirement is broken down until it becomes verifiable—that is, associated with a measurable acceptance criterion. The second step is the creation of the traceability matrix. A requirements traceability matrix is a table that links each requirement to the tests that verify it and to the evidence documenting the test results; it is the tool that reveals coverage gaps before testing begins.
The subsequent steps translate the matrix into an operational test bench:
- Modular test bench design: the stimulus, measurement, and control modules are separate, so that a new configuration requires replacing a single module rather than rebuilding the entire test bench.
- Standardized test procedures: each test is described by a procedure with defined parameters, sequence, and acceptance criteria, which can be executed with the same outcome by different operators.
- Measurement and control instrumentation: instruments are selected based on the critical parameters to be monitored, with accuracy appropriate for the acceptance criteria.
- Structured collection of evidence: Test data is recorded in a uniform format and linked to the verified requirement.
- Review of results: Results are compared against acceptance criteria, and deviations are analyzed before the requirement is closed.
This process requires the integration of multiple disciplines. Electrical engineering defines the interfaces and test conditions; software controls sequences and data acquisition; and the quality function ensures consistency among requirements, procedures, and evidence. Validation is reliable when these disciplines operate within a single document chain rather than separate archives.
Concrete Impacts
A test bench designed based on requirements has measurable effects on the program, particularly on traceability, timelines, and the quality of technical decisions. The main effects are as follows:
- Traceability and repeatability: Every result can be traced back to a requirement and a procedure, and the test can be repeated under the same conditions.
- Reduced verification time: Automation—even partial—of test sequences reduces the time spent on repetitive tasks.
- Decisions based on verified data: A system’s compliance is assessed based on objective evidence rather than subjective evaluations.
- Targeted use of engineering resources: Engineers focus on critical aspects and the analysis of deviations, rather than on manually preparing tests.
- Support for audits and certification: The documentation produced during testing is already organized for review by a third-party entity.
For defense systems, these benefits translate into greater operational reliability, because nonconformities are identified while they can still be corrected at a low cost.
RAIT88’s Perspective
At RAIT88, test benches are designed with a modular approach, allowing them to adapt to the various configurations of the systems being validated. Validation is based on compliance criteria defined by the customer: each test phase adheres to verified technical specifications, with standardized evidence-collection procedures and measurement instrumentation suited to the critical parameters of the system under test.
This approach ensures that requirements, tests, and results remain consistent from the beginning to the end of the program. The integration of the test benches with existing infrastructure is carried out in compliance with industry safety requirements, with particular attention to the protection of test data. Continuous monitoring of verification activities keeps processes aligned with technical specifications and allows for timely intervention in the event of anomalies or deviations.
A traceable validation is established prior to testing, involving the breakdown of requirements, the traceability matrix, and a test bench designed to generate evidence. Final acceptance testing is the result of this process, not the starting point. The natural next step is balancing automation with engineering judgment: which tests to automate, which to entrust to an operator, and how to document both within the same chain of evidence.
The approach described here stems from the operational experience RAIT88 has gained in contexts characterized by high technical complexity and stringent requirements, typical of the defense sector.
This article is part of a series dedicated to defense engineering. RAIT88 explores these topics in depth weekly on its blog.