In an automotive project, dozens or even hundreds of requirements may be defined for a vehicle, system, or component. Some of these requirements originate from standards and regulations, others are specified by the vehicle manufacturer or customer, and another group arises from product design, performance, durability, safety, and quality objectives. Ultimately, the project team must be able to demonstrate, through appropriate evidence, that the product meets the relevant requirements, and testing is one of the most important tools for generating such evidence. However, simply having a list of tests is not enough to manage this process; it must be clear why each test is performed, which requirement it evaluates, which specimen it will be performed on, and what project decision its result is intended to support.
This is where a Test Plan becomes important. An effective Test Plan connects product requirements with actual Verification and Validation activities and defines what needs to be tested, the applicable test method and reference, the required specimen and configuration, the number of specimens to be prepared, the acceptance criteria, the development stage at which the test will be performed, and how the result will be recorded and linked to the relevant requirement. Therefore, a Test Plan should not be viewed merely as an Excel file containing a few test names and dates; it is one of the main tools for managing the technical evidence needed to make informed product decisions.
What Is a Test Plan?
A Test Plan is a document or structured framework that defines, organizes, and makes project testing activities traceable before they are performed. Its format may vary depending on the organization and product complexity; for a simple component, a controlled table may be sufficient, while the Test Plan for a complex system or complete vehicle may include several test procedures, a requirements matrix, a specimen plan, schedules, and supporting documents. What matters is not the appearance of the document but its ability to maintain the relationship between the requirement, evaluation method, specimen, test conditions, acceptance criteria, and result.
A practical Test Plan should answer several fundamental questions: Which requirement is being evaluated? Why is testing an appropriate method for evaluating it? Which standard or procedure will be used? What specimen is required, and with which revision and configuration? What data must be recorded? What are the acceptance criteria? At what stage of development will the test be performed, and how will its result be used in the project's engineering decisions? If these questions are not clearly addressed, a project may perform numerous tests yet still lack sufficient or traceable evidence for certain requirements.
A Test Plan Should Start with Requirements
One of the most important principles of test planning is that tests should be derived from requirements, not requirements selected based on the tests available in a laboratory. Sometimes a project begins with a list of tests used for a previous product, available laboratory capabilities, or experience from a similar project, and then attempts to apply those tests to the new product. This approach may seem faster, but it increases the risk of performing unnecessary tests or overlooking new requirements.
The logical sequence is the opposite. Product requirements should first be identified and categorized, and then an appropriate Verification or Validation method should be determined for each requirement. One requirement may be verified through engineering analysis, another through inspection or measurement, and another may require physical testing. Therefore, not every requirement needs to become a test; testing is one method of generating evidence and should be included in the Test Plan when it is appropriate for the engineering question being addressed.
For example, if a vehicle seat has a requirement relating to structural strength, physical testing may be necessary to demonstrate compliance. However, a requirement concerning the dimensions of mounting points may be verified through measurement, while another requirement relating to component geometry may be evaluated by reviewing engineering drawings or models. An effective Test Plan starts with the requirement and identifies the evidence needed to demonstrate compliance, rather than attempting to find a testing machine for every requirement.
If the difference between Verification and Validation and the role of testing in these processes is not yet clear, the article “What Are Validation and Verification? The Difference Between Validation and Verification in the Automotive Industry” explores these concepts in greater detail.
What Information Should an Effective Test Plan Include?
The content of a Test Plan depends on the product and the organization's processes, but information such as requirement ID, test title, test objective, applicable standard or procedure, specimen type and quantity, part number and revision, configuration, test conditions, measurement parameters, acceptance criteria, development stage, responsibilities, schedule, and result status is generally important. In more complex projects, details such as fixtures, specimen preconditioning, special equipment, data acquisition systems, test sequence, test location, dependencies between tests, and conditions for specimen reuse may also form part of the plan.
Every field should serve a specific purpose. For example, recording the specimen revision is not merely an administrative task; if the design changes after testing, this information identifies which design revision the existing result relates to. Recording the number of specimens is also not just a logistical matter; if a test is destructive or multiple configurations need to be evaluated, specimen quantity directly affects project cost and schedule. A Test Plan is therefore valuable when its information helps control the actual risks associated with performing tests and using their results.
What Does a Simple Test Plan Look Like?
Suppose a vehicle seat assembly is under development. A simplified section of its Test Plan might have the following structure:
| Requirement | Evaluation Method | Reference | Specimen and Configuration | Stage | Acceptance Criteria |
|---|---|---|---|---|---|
| Seat structural strength | Physical testing | Applicable standard or regulation | Seat assembly, Rev. B | DV | As specified in the reference |
| Adjustment mechanism travel range | Functional testing and measurement | Project specification | Seat assembly, Rev. B | DV | As specified in the specification |
| Mounting point dimensions | Measurement | Engineering drawing | Seat assembly, Rev. B | DV | Within specified tolerances |
| Production-representative product performance | Project-defined testing | Applicable test procedure | Production-representative specimen | PV | As specified in project requirements |
In an actual project, this table should contain additional details, including requirement IDs, standard versions, specimen quantities, test conditions, responsible personnel, planned dates, and result status. However, even this simple example demonstrates an important principle: every test should be traceable to a specific requirement or engineering objective. If a test appears in the plan and the team cannot explain what its result is intended to demonstrate, the value of performing that test should be reconsidered.
Acceptance Criteria Must Be Defined Before Testing
One of the most important elements of a Test Plan is the Acceptance Criteria. Before testing begins, it must be clear which measurable, observable, or referenced criteria will be used to evaluate the result. Defining criteria after reviewing the test result can influence its interpretation and increase the risk of subjective decision-making.
In standardized testing, acceptance criteria are generally derived from the applicable standard or regulation. In development testing, the criteria may come from engineering specifications, customer requirements, or internal design objectives. In a Pre-Test, the objective may not involve a Pass/Fail decision at all; instead, the engineering team may want to investigate design margins, failure modes, or deformation behavior. In such cases, the Test Plan should make it clear from the beginning that the objective is not to determine whether the specimen passes or fails, but to generate data for a specific development decision.
Statements such as “must not deform excessively” or “must perform adequately” are not sufficient for a professional Test Plan. Criteria should be numerical wherever possible or refer to a clearly defined source so that the result can later be interpreted without ambiguity.
How Should the Test Specimen Be Defined?
A generic product name is not sufficient to define a test specimen. Expressions such as “front seat,” “vehicle X,” or “production component” may be understandable in everyday communication, but they do not provide sufficient traceability for test results. The Test Plan should specify which Part Number, Revision, product variant, or configuration will be tested and, where relevant to the result, record characteristics such as material, supplier, software version, calibration, and auxiliary equipment.
This becomes even more important for complete vehicles because the number of influential variables increases. Vehicle mass, tires, installed equipment, ECU software versions, system status, and other parameters may be important depending on the test method. Therefore, specimen configuration management should be part of test planning rather than an activity performed after the result has been obtained.
If the design changes from Revision B to Revision C after testing, it should be possible to determine how that change affects the requirements and previous results. Without traceability between the specimen and its result, deciding whether the earlier test remains valid becomes difficult.
How Is the Required Number of Specimens Determined?
There is no universal rule of “one specimen per test.” The required quantity may be specified by the standard or test procedure, or it may be selected based on development objectives, expected variability, risk level, and the project's statistical plan. Some tests are destructive, making the specimen unsuitable for further use, while other activities may be performed without significantly changing the specimen.
During Design Verification (DV), several design alternatives may need to be compared; during Production Validation (PV), production-representative specimens become more important; and in Type Approval or Conformity of Production (CoP), specimen requirements may be established by regulations. Therefore, specimen quantity should be determined based on the test objective and applicable reference, rather than being decided at the end of the project according to the number of available components.
Specimen planning should be considered at the overall project level. If a component is scheduled to undergo five different tests, it is necessary to determine whether the same specimen can be used for all five activities or whether the first test will alter its initial condition and affect subsequent testing.
Test Sequence Can Affect the Results
When several tests are planned for the same specimen, the Test Sequence becomes important. A test may cause deformation, fatigue, wear, aging, temperature increases, or changes in a component's condition, leaving the specimen unsuitable for the initial conditions required by the next activity. Even repeatedly installing and removing a specimen from a fixture can affect certain tests.
Therefore, the test sequence should be established before testing begins and should not be determined solely by the earliest available equipment slot. Non-destructive tests can often be performed before destructive tests, but even this general approach must be checked against the applicable test methods. The objective is to maximize specimen utilization without compromising the validity of the results.
Appropriate specimen allocation and test sequencing can reduce the number of specimens required in expensive projects. However, saving specimens should never result in unreliable test results due to previous loading history or changes in the specimen's initial condition.
How Do DV and PV Affect the Test Plan?
The Test Plan should account for the product's maturity stage. A test performed during Design Verification (DV) may have a different objective and specimen from the same activity performed during Production Validation (PV). In DV, the main focus is on verifying the design, whereas in PV, the product and manufacturing process are closer to production conditions, and the question is whether a production-representative specimen maintains the expected performance.
For this reason, some tests may be performed during both stages, others only during DV, and others only during PV. Repeating a test should also have a clear justification. If a test was performed during DV on a development specimen and the characteristic being evaluated may be affected by production tooling or manufacturing processes, repeating it during PV may be appropriate. However, automatically repeating every DV test during PV without reviewing the requirements and risks is not necessarily an effective approach.
The article “What Are DV and PV in the Automotive Industry? From Design Verification to Production Validation” explains the different objectives of these stages and the maturity levels of the specimens used.
What Is the Role of Pre-Testing in a Test Plan?
A Pre-Test is valuable when it is used to reduce a specific risk or uncertainty. If the project team lacks sufficient confidence in design margins, potential failure modes, or the likelihood that a particular configuration will perform as expected, a Pre-Test may be planned before the main test. In this case, the Test Plan should define exactly which engineering question the Pre-Test is intended to answer and what decision its result is expected to influence.
The Pre-Test specimen is not necessarily the same as the specimen used for formal testing, and its conditions may not exactly follow the formal test method. These differences should be recorded in the plan so that the Pre-Test result is not later mistaken for a formal test result or incorrectly generalized to another configuration.
The article “What Is a Pre-Test and How Is It Different from a Formal Test?” discusses the applications and limitations of Pre-Testing in greater detail.
How Is a Standards-Based Test Plan Different?
When testing is performed to demonstrate compliance with a standard or regulatory requirement, the project team has less flexibility in defining the method. The applicable standard or regulation may specify specimen preparation, test setup, equipment, test conditions, measurement procedures, and acceptance criteria, and the Test Plan must accurately reflect these requirements.
In such cases, the standard number alone is not always sufficient. The applicable standard edition, referenced version, or series of amendments to the regulation must also be identified, and its applicability to the product must be assessed. If the plan simply states “R17 Test,” it is still unclear which version, configuration, and specific requirements are being addressed.
To review the tests and standards available at TAT, you can use the Table of Available Tests. This table can help identify the relevant tests and standards, but the project's Test Plan must be prepared according to the product's actual requirements and the reference documents applicable to that project.
What Is the Role of a Test Plan in Type Approval?
In a Type Approval project, tests provide part of the evidence needed to demonstrate that a defined product Type complies with the applicable requirements. Therefore, the Test Plan should be aligned with the project's regulatory requirements matrix and identify which tests, approvals, documents, or other evidence are required for each requirement and which configuration must be submitted for evaluation.
This plan is not necessarily identical to the product development Test Plan. The engineering team may perform tests beyond the minimum regulatory requirements for development purposes, while the Type Approval plan focuses on the evidence needed for the approval process. Some tests may be common to both plans, but the intended use of the result must be defined from the beginning.
The article “What Is the Difference Between Type Approval and Homologation?” explains the role of testing in the Type Approval process and how it differs from Homologation.
Test Scheduling Is More Than Choosing a Date
Test scheduling must account for the project's actual dependencies. When will the specimen reach the required design revision? When will the fixture be ready? Is specific preconditioning required? Must another test be completed before this activity? When can the laboratory perform the test? If the result is a failure, how much time will be needed for root cause analysis, design modifications, specimen manufacturing, and retesting?
One common mistake is to schedule critical tests immediately before a major project milestone while assuming that every test will pass on the first attempt. Such a plan leaves little room for engineering learning. A realistic Test Plan should treat the possibility of failure as a manageable risk rather than an event for which no time has been allocated.
For this reason, scheduling should account not only for test execution time but also for data analysis, engineering decisions, and retesting when necessary.
Laboratory Selection Is Also Part of Test Planning
A project may require tests involving different equipment, expertise, and accreditation scopes, and a single laboratory may not cover all of them. Therefore, the testing laboratory should ideally be selected before the specimens are ready. Equipment capacity, required fixtures, scheduling, the ability to measure the necessary parameters, and, where applicable, the laboratory's Scope of Accreditation can all affect the plan.
If the project requires a test result issued under accreditation, simply having the necessary equipment does not mean that the specific test is included within the laboratory's Scope of Accreditation. The Test Plan should address this in advance to avoid discovering at the end of the project that the resulting report cannot be used for its intended purpose.
What Should the Test Plan Define Before Sending a Specimen?
When a specimen is ready to be sent to the laboratory, decisions about the standard, design revision, specimen quantity, or fixture should not still be unresolved. Ideally, the Test Plan should already define which specimen and configuration are required, which documents must accompany it, how the test will be set up, which auxiliary components are needed, what preconditioning must be performed, and whether the specimen can be reused after testing.
This is directly related to specimen preparation. The article “What Should Be Checked Before Sending a Vehicle or Component to the Laboratory?” explains the differences between Validation, Type Approval, and CoP specimens, as well as configuration, documentation, fixtures, transportation, and specimen condition. The Test Plan should account for these activities in advance so that specimen preparation does not become a last-minute task.
The Test Plan Must Be Reviewed After Design Changes
A Test Plan is not a static document created at the beginning of a project and left unchanged until completion. Changes in design revision, supplier, material, or manufacturing process, test failures, and even changes in requirements can affect the plan. After every significant change, it is necessary to determine which tests and results are affected and whether the previous evidence remains valid.
Decisions about retesting should be based on an Impact Analysis. If a change has no effect on the requirement or the behavior being evaluated, repeating the test may not be necessary. However, if the change affects load paths, geometry, material, software, calibration, or any other characteristic influencing the result, the validity of the previous test result must be reassessed.
For this reason, the Test Plan should also record the status of each activity, such as Planned, Scheduled, Completed, Passed, Failed, or Retest Required. This status tracking helps turn the Test Plan into an up-to-date picture of the project's Verification progress.
How Are Test Plans and DVP&R Related?
In the automotive industry, the term DVP&R, or Design Verification Plan and Report, is also widely used. DVP&R provides a structure for planning Design Verification activities and recording their results, making it closely related to the Test Plan. However, the two terms should not be considered exact synonyms in every company or project; document structures and responsibility boundaries may differ.
In one organization, DVP&R may serve as the primary Design Verification document, with test information managed directly within it. In another organization, separate execution-level Test Plans may be used and linked to the DVP&R. More important than the document's name is traceability between requirements, Verification methods, specimens, acceptance criteria, and results.
Therefore, the relationship between the Test Plan and DVP&R should be defined within the project's management structure. If both documents are used, information concerning requirements, test status, results, and design changes must remain consistent between them to prevent conflicting records or unnecessary duplication of activities.
Who Is Responsible for Preparing the Test Plan?
A Test Plan should generally not be prepared solely by the laboratory or by one person at the end of the development process. The design team understands the product requirements and failure modes, test engineers understand execution methods and limitations, project management coordinates schedules and milestones, and in regulatory projects, the compliance or Type Approval team must incorporate legal requirements into the plan. Therefore, test planning for complex products is a cross-functional activity.
The laboratory can provide important information about test feasibility, fixtures, equipment, specimen conditions, and scheduling. However, responsibility for defining requirements and deciding whether the Verification program is sufficient remains at the project level. A laboratory cannot determine which set of tests is sufficient for complete product Validation based solely on its available equipment.
For projects where applicable requirements, test methods, or the structure of the testing program have not yet been defined, TAT Engineering and Consulting Services can support requirements review, test planning, and the technical aspects of the Validation process.
What Makes an Effective Test Plan?
An effective Test Plan is not necessarily the one with the greatest number of tests or the most columns. Its value lies in making it possible to understand what will be evaluated, why, how, on which specimen, at what time, against which acceptance criteria, and which requirement or decision the result is intended to support. Tests that do not address any specific requirement or risk should be questioned, and requirements without a defined Verification method should be identified.
The Test Plan should also evolve with the project. Design revisions, test failures, supplier changes, Pre-Test results, and engineering decisions may require updates, and these changes must be controlled. If the Test Plan is merely a file created at the beginning of the project and never reviewed again, it loses much of its value.
Ultimately, the purpose of test planning is not to perform more tests, but to perform the right test, on the right specimen, at the right time, to answer the right question. When requirements, specimens, methods, acceptance criteria, and results are connected, testing becomes a manageable part of the product development process rather than an isolated laboratory activity.