50 Specific Ways to Improve Your Testing - 01

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Item 1: Involve Testers from the Beginning
Testers need to be involved from the beginning of a project's life cycle so they can understand exactly what they are testing and can work with other stakeholders to create testable requirements.

Defect prevention is the use of techniques and processes that can help detect and avoid errors before they propagate to later development phases. Defect prevention is most effective during the requirements phase, when the impact of a change required to fix a defect is low: The only modifications will be to requirements documentation and possibly to the testing plan, also being developed during this phase. If testers (along with other stakeholders) are involved from the beginning of the development life cycle, they can help recognize omissions, discrepancies, ambiguities, and other problems that may affect the project requirements' testability, correctness, and other qualities.

A requirement can be considered testable if it is possible to design a procedure in which the functionality being tested can be executed, the expected output is known, and the output can be programmatically or visually verified.

Testers need a solid understanding of the product so they can devise better and more complete test plans, designs, procedures, and cases. Early test-team involvement can eliminate confusion about functional behavior later in the project life cycle. In addition, early involvement allows the test team to learn over time which aspects of the application are the most critical to the end user and which are the highest-risk elements. This knowledge enables testers to focus on the most important parts of the application first, avoiding over-testing rarely used areas and under-testing the more important ones.

Some organizations regard testers strictly as consumers of the requirements and other software development work products, requiring them to learn the application and domain as software builds are delivered to the testers, instead of involving them during the earlier phases. This may be acceptable in smaller projects, but in complex environments it is not realistic to expect testers to find all significant defects if their first exposure to the application is after it has already been through requirements, analysis, design, and some software implementation. More than just understanding the "inputs and outputs" of the software, testers need deeper knowledge that can come only from understanding the thought process used during the specification of product functionality. Such understanding not only increases the quality and depth of the test procedures developed, but also allows testers to provide feedback regarding the requirements.

The earlier in the life cycle a defect is discovered, the cheaper it will be to fix it. Table 1.1 outlines the relative cost to correct a defect depending on the life-cycle stage in which it is discovered.[1]

[1] B. Littlewood, ed., Software Reliability: Achievement and Assessment (Henley-on-Thames, England: Alfred Waller, Ltd., November 1987).

Table 1.1. Prevention is Cheaper Than Cure: Error Removal Cost Multiplies over System Development Life Cycle Phase  Relative Cost to Correct  
Definition  $1  
High-Level Design  $2  
Low-Level Design  $5  
Code  $10  
Unit Test  $15  
Integration Test  $22  
System Test  $50  
Post-Delivery  $100+