How to Develop a Successful Test Strategy

- key points of how to develop a successful test strategy or test automation strategy, write a test strategy document and template and improve performance of the process.

This ATE, Automatic Test Equipment tutorial is split into several pages each of which address different aspects of ATE Automatic Test Equipment and their operation:

The development of a test strategy / process or testing strategy for an electronics product is just as important as the development of the product itself. It is an unfortunate fact of life that not all products will work once they have been manufactured and it is necessary to test the product before it is shipped to ensure that it is operational.

The test strategy or testing process will need to be developed around the product, and the available equipment. When creating a testing strategy it is necessary to take account of many other aspects of the product including its design, the complexity of the boards and many other factors. It may be necessary to ensure that elements of the design are changed to enable testing to be accommodated more easily and in a more cost effective manner. As a result it is necessary to develop the test strategy from the earliest stages on the development of the product.

Elements of creating a test strategy

In order to create a test strategy, it is necessary to start at the beginning of a project and then carry the development and implementation forward throughout the whole of the development and production lifecycle. In order to ensure that the testing strategy is carried forward, it is wise to create a test strategy document, and update this as the development and production elements of the project move forward.

The main elements of the test strategy lifecycle may include the following:

1. Analyse the product:   One of the first tasks to undertake is to completely review the proposed product. It will be possible to gain a good idea of the construction of it, and form a view of the anticipated components and technologies it should be possible to estimate the anticipated failure rates.


2. Review available test equipment:   While many would like to tailor the test equipment to the product and buy new test equipment, this is not normally possible. It is normally necessary to re-use existing test equipment and to design the product so that it is optimised for the test equipment that already exists. With a knowledge of the technologies used in the proposed product it will be possible to asses the existing test equipment to ensure it will be suitable for testing the new product.


3. Review test opportunities:   It will be necessary to review the areas in which assemblies can be tested, both during the pilot production runs when more failures would be expected as well as later in its life when the processes will have matured and the line settled down.


4. Create test strategy document:   In order to define what needs to be achieved it is necessary to create a test strategy document. This will set down the aims of the test strategy in a form that can be reviewed and then implemented. It is vital that all parties agree to this so that any design for test strategies can be implemented during the early design stages for the product.


5. Implement test strategy:   It is necessary to implement the test strategy from the earliest stages of the deign of the product. Elements of design for test will need to be implemented from the concept stages of the product through to the time when printed circuit boards and ASICs are committed. By ensuring that any design for test measures are introduced, the testing of the product can be greatly simplified and the test coverage increased to a level where few failures are missed.


6. Collect metrics:   One key element of any test strategy is to collect metrics. In this way commonly occurring problems can be seen and rectified. In this way the production process can be improved and costs reduced. Only by collecting metrics and analysing them quickly can process improvements be achieved.


7. Review and change test strategy and testing:   One of the key elements in any test strategy is to incorporate regular reviews of the product and be prepared to change even after the product has been in production for some while. This costs additional money and once a product has completed its development, this is rarely available and as a result costs may be higher than necessary because the testing is not continuing to be optimised. It is normally advisable to make changes to the test strategy once a product has been in production. It may be possible to omit some tests which rarely produce results or it may be necessary to introduce others to reduce fault find time. These improvements to the test strategy can only be implemented if funding is available.

Test strategy document and template

In order to define a test strategy and have it reviewed by all interested parties and agreed, it is necessary to write a test strategy document. A test strategy document template is given below. The test strategy document template defines some sections that could be sued for a test strategy document. Naturally this is only a general template, and will need to be adapted for the particular circumstances and requirements.

The test strategy document template can include the following sections and subsections:

1. Header and company standard initial sections:   This section will include the company header and initial pages. They will include elements such as the review and release / issue history.


2. Abbreviations:   A table of all abbreviations used within the document needs to be included to ensure that any abbreviations used are defined to prevent any misunderstanding. In addition tot his, the first time any abbreviation is used, the full version should also be used in line with good technical document writing practice.


3. Introduction:   This section will comprise a number of subsections that will, as a whole, set out the initial information for the reader to understand what is being addressed. The subsections addressed may include the following:
   
   
   • Initial outline:   At the very beginning of the document it is necessary to outline the basic situation and what is to be addressed and why. It will effectively state the requirement in very broad terms. This will enable the reader to understand what is being addressed within the document.
   • Applicability and scope:   This will detail areas to be included within the document stating what the document is applicable to as well as detailing any limits to the application of the document.
   • Document structure:   This section will detail the structure of the document, giving a short view of what each section contains.
   • Referenced documents:   A full list of all referenced documents should be given. Where applicable, their location should also be listed.


4. Requirements:   This section will give a more in-depth view of the requirements. It will detail the product and detail the area to which the test strategy will apply in detail.


5. Product description:   It may be worth providing a review of the product itself. This could detail each assembly within the product detailing and features that may need to be addressed specifically from a testability viewpoint. Within this section, anticipated yields and volumes can be specified.


6. Examination of current situation:   It may be necessary to look at the starting points and what equipment and space is available for the testing area. With cost often a major issue, re-use of existing test equipment and facilities may be an issue. If the test strategy is to apply to a new product, it may be that the testing will need to sue an area where another products, each with their own test strategies are currently tested. These issues will impose constraints on how any new test strategy, or a test strategy for a new product can be implemented.


7. Proposed strategy overview:   This section of the test strategy document can detail the test strategy to be adopted. It should address the different forms of testing to be used, and at what stages. It should also take on board the expected yield rates and sue this to not only determine the types of test to be used, but analysing the required throughput and the expected test times it can detail the number of test stations required at each stage of testing.


8. Test strategy for individual assemblies:   Dependent upon the nature of the product, its complexity and the number of assemblies, it may be worth detailing the test strategy for each assembly and sub-assembly within the overall product in a separate section to the one above. It can detail each subassembly:
   
   
   • Assembly A:   Details should be provided for the method or methods used for testing the assembly.
   • Assembly B:   Details should be provided for the method or methods used for testing the assembly.
   • Further assemblies as required ..:   .. details supplied for each assembly...
9. Summary and recommendations:   This section will summarise the document, bringing together the overall recommendations. It will propose a way forwards, summarising aspects including lead times, test development required, investment in new equipment, and the overall costs. It is also useful to include a return on investment calculation to justify the expenditure.

This test strategy document template is only a proposal and will need to be adjusted for the given circumstances and company requirements. It should be taken as a starting point to develop the test strategy document that will fulfil the requirements of defining the test strategy while meeting the overall company requirements.

Summary

By adopting a sound test strategy from the early design stages of a product, production costs can be kept to a minimum while maintaining a high quality product. This is exactly where some of today's top manufacturers score, and are able to deliver cheap reliable product.

Further pages from this tutorial
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