Suppose a component or vehicle has spent months in the design and development stage and is now ready to be sent to a laboratory for standardized testing. If the test result shows that one of the requirements has not been met, the issue is not limited to the cost of the test itself; a new specimen may be required, the design may need to be changed, the component may have to be rebuilt, and part of the project schedule may be delayed. In such circumstances, it is natural for the engineering team to want as much information as possible about the product before reaching the final test.
One tool that can be used in such a situation is a Pre-Test. The purpose of a Pre-Test is not to determine the result of the formal test in advance or guarantee that the product will pass; its primary purpose is to obtain more information about product performance before entering a stage where a formal result or an important project decision depends on the outcome, identify recognizable risks, and provide an opportunity to modify the design or specimen if necessary. This difference in purpose defines the main distinction between a Pre-Test and a formal test.
What Is a Pre-Test?
A Pre-Test can be described as a preliminary evaluation or test performed before the main or formal test to obtain information about specimen performance. Depending on the project, the Pre-Test may closely follow the final test method or reproduce only some of its important conditions and parameters. The degree of similarity to the formal test should be determined by the objective of the Pre-Test rather than simply referring to every preliminary experiment as a Pre-Test.
For example, if a vehicle seat development team is concerned that a particular area of the structure may not perform adequately during a load test, a specimen may be evaluated under relevant conditions before the final test to identify structural behavior, deformation, or a potential Failure Mode. In another project, the purpose of the Pre-Test may be to evaluate the performance of a system in several different Configurations so that the engineering team has more data for decision-making before selecting the final Configuration.
Therefore, a Pre-Test does not have a fixed format that applies to every product. Sometimes almost the same Setup as the main test is used with a development specimen; sometimes only part of the loading or test conditions is evaluated; and sometimes the objective is simply to compare two designs. What defines a Pre-Test is its preliminary and development-oriented purpose.
How Is a Formal Test Different from a Pre-Test?
In a formal test, the product is evaluated according to the reference, method, conditions, and criteria defined for the relevant process, and the result may be used for conformity assessment, product approval, or other related formal decisions. In such a test, specimen identity and Configuration, test method, equipment, environmental conditions, data recording, and result reporting have defined importance, and if the activity is performed within the laboratory’s Scope of Accreditation, the requirements associated with that scope must also be followed.
A Pre-Test generally allows greater flexibility because its primary purpose is to generate information for engineering decision-making. The project team may want to stop the test earlier, record additional parameters, inspect the specimen after observing a particular behavior, or compare several Configurations. Such flexibility can be highly valuable during development, but it is also one of the reasons why a Pre-Test result should not automatically be considered equivalent to a formal test result.
| Pre-Test | Formal Test |
|---|---|
| The primary objective is to understand product behavior and reduce project risk | The objective is to evaluate the product according to defined requirements and processes |
| It can be designed around the project’s engineering question | It must follow the referenced conditions and method |
| The specimen may still be at the development stage | The specimen must comply with the requirements of the relevant process |
| Multiple designs or Configurations may be evaluated | The tested Configuration must be defined and traceable |
| The result is primarily used for development decision-making | The result may form the basis of a formal evaluation or related decision |
| Passing does not guarantee the outcome of the formal test | The result is reported according to the conditions and applicable criteria of that test |
Does a Pre-Test Have to Be Performed Exactly According to the Standard?
Not always; the answer depends on the objective of the Pre-Test. If the goal is to provide the project team with a closer estimate of how the product will behave in the final test, it makes sense for the Pre-Test conditions to follow the referenced method as closely as possible. However, if the engineering question is more limited—for example, comparing two designs or identifying the point at which deformation begins—it may not be necessary to perform every step of the standard.
However, the further the Pre-Test moves away from the conditions of the main test, the more carefully its result must be interpreted. If the Fixture is different, the loading rate changes, the specimen has a different Configuration, or some of the standard conditions are omitted, the result may still be valuable for product development but should not be generalized to the main test result without analysis. Therefore, before performing a Pre-Test, it is useful to define which parts of the main test need to be reproduced and which modifications are acceptable for the project’s engineering objective.
When Is a Pre-Test Valuable?
A Pre-Test provides the greatest value when the cost of discovering a problem during the main test is high and there is still an opportunity to modify the product. If the final specimen is very expensive, manufacturing a new specimen takes a long time, the test is destructive, or access to laboratory equipment is limited, identifying a design weakness at the preliminary stage can prevent significant cost and delay.
A Pre-Test can also provide useful information in projects involving a new design, significant changes compared with a previous product, a change in material or supplier, or insufficient confidence in the design Margin. Similarly, if the product is still under development and several design options are being compared, a preliminary evaluation may help identify a more suitable Configuration for continued development.
However, a Pre-Test should not be performed simply because “we always perform a Pre-Test before the main test.” Every testing activity should answer a specific question. If the design is well understood, sufficient evidence already exists, and the test risk is low, a Pre-Test may provide limited value relative to its time and cost.
When Might a Pre-Test Not Be Necessary?
More testing does not always lead to better engineering decisions. If the product has undergone only a very limited change and the effect of that change is adequately covered by valid previous evidence, analysis, or appropriate Verification, performing a complete Pre-Test may not be necessary. In another project, the cost of the Pre-Test may be almost as high as the main test while sufficient specimens are readily available; in such circumstances, it is necessary to determine whether the additional information generated by the Pre-Test is actually worth the associated cost and time.
The appropriate decision should be based on risk, design maturity, cost of failure, number and value of specimens, level of product knowledge, and the schedule impact of failing the main test. A Pre-Test should therefore be viewed as an engineering risk-management tool rather than a mandatory and fixed stage in every project.
Does Passing a Pre-Test Guarantee Passing the Formal Test?
No. Even if the Pre-Test is performed under conditions very close to the formal method, its result should not be interpreted as a guarantee that the subsequent test will be passed. The specimen used may be different, production Tolerances may have an effect, test conditions or Setup may differ, and even if all these factors are controlled, the result from a single specimen cannot represent every possible variation in the product.
This is particularly important when the Pre-Test is performed on a Prototype or hand-built specimen while the formal test uses a specimen with a higher maturity level or a different Configuration. A Prototype may behave differently because of local reinforcement, a different manufacturing process, or non-production components and may not accurately represent the subsequent product. Therefore, the Pre-Test result should be analyzed with a clear understanding of the specimen Configuration and maturity level.
Is an Unsuccessful Pre-Test a Bad Outcome?
Not necessarily. In fact, one of the purposes of a Pre-Test is to reveal a problem while there is still an opportunity to make corrections. If a development specimen behaves inadequately during a Pre-Test, the engineering team can investigate the Failure Mode, identify the cause, and modify the design before entering the main test. From this perspective, an unsuccessful Pre-Test that produces useful information can be more valuable to the project than a test that provides only a Pass/Fail result without revealing much about the behavior of the design.
What matters is how the data are used. If, after a failure, the specimen is simply reinforced so that it can pass the next test without identifying the root cause of the problem, the engineering value of the Pre-Test is reduced. The result should instead be linked to the Requirement, design, and Failure Mode, and it should be determined exactly what issue the proposed change addresses and whether it affects other product characteristics.
How Is a Pre-Test Related to Validation and Verification?
Pre-Test, Validation, and Verification are not synonymous terms. Verification and Validation are engineering objectives, while Testing is one of the methods that can be used to generate evidence within these processes. A Pre-Test is a type of preliminary testing activity that, depending on the project objective, can contribute to Verification or Validation.
For example, during Design Verification, an engineering team may use a Pre-Test to perform an initial assessment of a strength Requirement and identify a potential design weakness before the final test. In another project, a Pre-Test may form part of Validation activities and be used to assess product behavior under conditions representative of the intended application. Therefore, the role of a Pre-Test is determined by the test objective and the engineering question being addressed.
For a more detailed explanation of these concepts, the article “What Are Validation and Verification? The Difference Between Validation and Verification in the Automotive Industry” explains the role of Testing in V&V and the different objectives of these two processes.
A Practical Example: Vehicle Seat Pre-Testing
Suppose a new vehicle seat is being developed and the engineering team needs to evaluate its performance against the relevant strength requirements. Before sending the final specimen for testing, analyses indicate that one area of the Frame may have a limited Margin. One option is to manufacture the final specimen and proceed directly to testing; another is to first evaluate a development specimen in an appropriate Pre-Test to better understand the actual behavior of the structure.
During the Pre-Test, the project team may focus on deformation in the area of interest in addition to the primary data, observe specimen behavior through different stages of loading, and inspect areas of deformation or failure after the test. If the design weakness is confirmed, corrective changes can be made before the next specimen is manufactured. Once the design reaches an appropriate level of maturity, the specimen for the main test can be prepared with a defined Configuration and documentation.
For information about the relevant seat strength test, you can visit the Vehicle Seat Strength Test – ECE R17 page on the TAT website. The existence of a dedicated test page does not mean that every Pre-Test must be performed exactly according to R17; the purpose and conditions of the Pre-Test should be defined according to the needs of the project.
Can a Pre-Test Specimen Also Be Used for the Formal Test?
The answer depends on the type of test, the Pre-Test conditions, and the condition of the specimen. If the Pre-Test has subjected the specimen to loading, deformation, wear, assembly and disassembly, or any other change affecting relevant characteristics, reusing it may influence the result of the subsequent test. In destructive testing, a specimen that has been damaged generally cannot be considered representative of the initial condition required for a subsequent test without further assessment.
Even in non-damaging Pre-Tests, it is necessary to determine whether the specimen’s previous use could affect the main test result. The decision should not be based solely on visual appearance; a component may show no visible damage while having been subjected to stresses or cycles that alter its subsequent behavior. Therefore, the specimen plan should identify before the Pre-Test which specimens are intended for development activities and which are reserved for the main test.
How Important Is Specimen Configuration in a Pre-Test?
If the purpose of the Pre-Test is to predict behavior in the formal test, specimen Configuration becomes highly important. Differences in material, thickness, attachment location, welding method, Fixture, software, auxiliary components, or even design Revision can change the result. The greater the difference between the Pre-Test specimen and the final specimen, the more cautiously the result must be generalized to the final product.
At early stages of development, using a Prototype may be entirely appropriate; the objective at that stage may be to understand the Failure Mode rather than accurately predict the final result. However, this limitation should be recorded in the report and engineering decision. A statement such as “the Pre-Test was successful” does not provide enough information for subsequent decision-making unless it also identifies which specimen, which Revision, and under what conditions the test was performed.
How Can a Pre-Test Reduce Project Costs?
Simply performing a Pre-Test does not reduce project cost; if it is conducted without a clear objective, it can actually create additional expense. Economic value is created when the Pre-Test reduces the likelihood of discovering an expensive problem late in the project. If failure in the main test would require manufacturing a new specimen, booking the laboratory again, modifying Tooling, or delaying a project Milestone, identifying the same problem using a development specimen can create significant value.
For this reason, three things should be defined before deciding to perform a Pre-Test: What risk are we trying to reduce, what decision will the test result change, and what is the cost of discovering the problem at the next stage? If there is no clear answer to these questions, a Pre-Test may not be the appropriate activity for the project.
What Should Be Defined in Advance for a Useful Pre-Test?
Before testing begins, the objective should be translated into a clear engineering question. The reference standard or method, the elements to be reproduced or simulated, specimen Configuration and Revision, Setup and Fixture, measurement parameters, test stop conditions, and the method for analyzing the result should preferably be defined in advance. If the objective is to compare several designs, the test conditions should also be sufficiently controlled so that the observed differences can genuinely be attributed to the designs.
In projects that will proceed to formal testing after the Pre-Test, specimen planning is also highly important. The number of specimens, possibility of reuse, test sequence, and time required for design modifications and manufacturing a new specimen should all be included in the plan. For specimen preparation, the article “What Should Be Checked Before Sending a Vehicle or Component to the Laboratory?” explains details relating to the standard, Configuration, documentation, Fixture, and the differences between Validation, Type Approval, and CoP specimens.
Can the Laboratory Design the Pre-Test?
The laboratory can contribute to defining the test procedure and assessing its feasibility, but the main Pre-Test question should originate from the needs of the project. The development team should know which Requirement, risk, or Failure Mode needs to be investigated and what decision the result is intended to support. Once this objective has been established, appropriate decisions can be made regarding the Setup, measurement method, and test conditions.
For projects where the applicable standards, test program, or appropriate evaluation method have not yet been determined, TAT Engineering and Consulting Services can support requirements review, test planning, and the technical aspects of the product validation process. These services do not guarantee the outcome of a formal test; their purpose is to support better definition and planning of the project’s technical activities.
How Should a Pre-Test Result Be Interpreted?
One common mistake is to record a Pre-Test result using only the words Pass and Fail. If the purpose of the test is product development, the information obtained about specimen behavior may be more important than the final result itself. The point at which deformation begins, force-displacement behavior, the conditions under which a system activates, Failure Mode, and differences between specimens can all provide information that shapes the next design decision.
A Pre-Test report should preferably identify which specimen was tested, including its Revision and Configuration, which conditions were the same as or different from the main test, what data were recorded, and the extent to which the result can be generalized. Such documentation helps prevent the project team from later attributing the result of one development specimen to a different Configuration.
A Pre-Test Should Reduce Risk, Not Simply Add Another Test to the Project
The value of a Pre-Test does not lie in the number of tests performed; it lies in the information it provides to the project team before a costly decision is made. If a Pre-Test can reveal a design weakness earlier, identify a more suitable Configuration, or show that the product is not yet ready for the main test, it can help prevent additional specimen builds, repeated testing, and project delays. In contrast, a Pre-Test performed without a clear question or a plan for using the result is simply an additional activity.
For this reason, before deciding to perform a Pre-Test, it is useful to ask: What do we still not know about the product, what risk does this uncertainty create for the main test, and what decision is the Pre-Test result expected to change? If the answers to these three questions are clear, an appropriate method and specimen can be selected, turning the Pre-Test into a purposeful part of the development process rather than an informal and repetitive version of a test that will simply be performed again later.