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Consumer Release Testing is high cost, low value risk management theatre

Despite the historical advice of Harold Dodge that “you cannot inspect quality into a product” and the contemporary advice of Don Reinertsen that “testing is probably the single most common critical-path queue” the Release Testing antipattern remains prevalent in the IT industry, and is by no means limited to standalone applications.

Consider the development of a consumer application that requires data from a provider application in order to fulfill its business capabilities. The consumer team contains developers and testers collaborating upon the Testing Pyramid strategy, which recommends unit/acceptance tests over end-to-end tests on the basis that test execution time is proportional to System Under Test scope. This means the necessary provider interactions are test-driven by the consumer team using the Test Stub pattern, which creates a lightweight provider implementation to supply canned responses back to the consumer.

Consumer Release Testing - Product Team Stubbed Provider

By using a stub the consumer interactions with the provider can be tested in a minimal System Under Test, which ensures that changes made by the consumer team produce fast and deterministic feedback. Success and failure scenarios (e.g. socket failure, socket timeout, provider error code) can be rapidly developed without relying upon a running provider instance, and the consumer team should be capable of rapidly responding to changing requirements in the future.

However, in many IT organisations the consumer team will be hindered by Consumer Release Testing – a phase of post-development end-to-end regression testing of the full consumer and provider stack, performed by a segregated testing team on the critical path.

Consumer Release Testing - Consumer Release Testing

The desire for provider risk mitigation is understandable given that consumer revenues are to an extent dependent upon the provider, but Consumer Release Testing exacerbates the original flaws of Release Testing:

  1. Extensive end-to-end testing – including both consumer and provider in System Under Test scope increases test execution time and maintenance costs
  2. Independent testing phase – dividing authority and responsibility for the consumer results in quality issues and feedback delays
  3. Critical path constraints – working on the critical path means the release testers will always be pressured to reduce test coverage to meet pre-agreed deadlines

By extending the Release Testing strategy it is evident that Consumer Release Testing is itself risk management theatre – it is highly unlikely to uncover any substantial defects in consumer/provider interactions without a significant increase in test coverage, which will drive up product lead times and opportunity costs.

A far more effective risk reduction strategy is to accept the conventional wisdom that testing is an activity not a phase, and move the blameless release testers into the consumer product team. This ensures that all team members are equally invested in product quality and empowers testers to focus upon higher-value activities such as exploratory testing, which has been described by Elisabeth Hendrickson as “particularly good at revealing vulnerabilities that no one thought to look for before“. For example, some exploratory testing off the critical path of the consumer against a running provider instance might uncover some additional error scenarios that would then be fed into the automated unit/acceptance tests.

Consumer Release Testing - Product Team Real Provider

A high value, low cost alternative to Consumer Release Testing is for the consumer and provider to actively cooperate in risk reduction, which can result in a substantial reduction in provider risk. The probability of a provider failure can be decreased by independently testing the conflated concerns of end-to-end testing as follows:

  • Connectivity: the consumer can test provider expectations of consumer connections via release time smoke tests and run time monitoring
  • Compatibility: the provider can test consumer expectations of messaging via build time Consumer Driven Contracts issued by the consumer
  • Conduct: the consumer can test its expectations of provider behaviour via build time API Examples issued by the provider

The cost of a provider failure can be reduced via incremental release strategies such as consumer-side Feature Toggles and provider-side Blue-Green Deployments. These practices encourage a provider release to be gradually phased into production usage, so that the consumer can switch back to the previous provider version if necessary.

This approach is a viable alternative to Consumer Release Testing, but it is of limited value without provider cooperation. If the provider cannot or will not participate in risk reduction then the consumer must assess risk based upon historical provider lead times. As large batch sizes increase risk an infrequent provider release schedule is indicative of heightened risk, and if the cost of failure is significant then a limited form of Consumer Release Testing may be deemed justifiable. In those circumstances the consumer development team should perform end-to-end tests off the critical path using a lightweight test client, so that the slow feedback loops and non-determinism of Consumer Release Testing are diminished.

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Release Testing is high cost, low value risk management theatre

Described by Elisabeth Hendrickson as originating with the misguided belief that “testers test, programmers code, and the separation of the two disciplines is important“, the traditional segregation of development and testing into separate phases has disastrous consequences for product quality and validates Jez Humble’s adage that “bad behavior arises when you abstract people away from the consequences of their actions“. When a development team has authority for changes and a testing team has responsibility for quality, there will be an inevitable increase in defects and feedback loops that will inflate lead times and increase organisational vulnerability to opportunity costs.

Release Testing - Develop and Test

Agile software development aims to solve this problem by establishing cross-functional product teams, in which testing is explicitly recognised as a continuous activity and there is a shared commitment to product quality. Developers and testers collaborate upon a testing strategy described by Lisa Crispin as the Testing Pyramid, in which Test Driven Development drives the codebase design and Acceptance Test Driven Development documents the product design. The Testing Pyramid values unit and acceptance tests over manual and end-to-end tests due to the execution times and well-publicised limitations of the latter, such as Martin Fowler stating that “end-to-end tests are more prone to non-determinism“.

Release Testing - Product Team

Given Continuous Delivery is predicated upon the optimisation of product integrity, lead times, and organisational structure in order to deliver business value faster, the creation of cross-functional product teams is a textbook example of how to optimise an organisation for Continuous Delivery. However, many organisations are prevented from fully realising the benefits of product teams due to Release Testing – a risk reduction strategy that aims to reduce defect probability via manual and/or automated end-to-end regression testing independent of the product team.

Release Testing - Release Testing

While Release Testing is traditionally seen as a guarantee of product quality, it is in reality a fundamentally flawed strategy of disproportionately costly testing due to the following characteristics:

  1. Extensive end-to-end testing – as end-to-end tests are slow and less deterministic they require long execution times and incur substantial maintenance costs. This ensures end-to-end testing cannot conceivably cover all scenarios and results in an implicit reduction of test coverage
  2. Independent testing phase – a regression testing phase brazenly re-segregates development and testing, creating a product team with authority for changes and a release testing team with responsibility for quality. This results in quality issues, longer feedback delays, and substantial wait times
  3. Critical path constraints – post-development testing must occur on the critical path, leaving release testers under constant pressure to complete their testing to a deadline. This will usually result in an explicit reduction of test coverage in order to meet expectations

As Release Testing is divorced from the development of value-add by the product team, the regression tests tend to either duplicate existing test scenarios or invent new test scenarios shorn of any business context. Furthermore, the implicit and explicit constraints of end-to-end testing on the critical path invariably prevent Release Testing from achieving any meaningful amount of test coverage or significant reduction in defect probability.

This means Release Testing has a considerable transaction cost and limited value, and attempts to reduce the costs or increase the value of Release Testing are a zero-sum game. Reducing transaction costs requires fewer end-to-end tests, which will decrease execution time but also decrease the potential for defect discovery. Increasing value requires more end-to-end tests, which will marginally increase the potential for defect discovery but will also increase execution time. We can therefore conclude that Release Testing is an example of what Jez Humble refers to as Risk Management Theatre – a process providing an artificial sense of value at a disproportionate cost:

Release Testing is high cost, low value Risk Management Theatre

To undo the detrimental impact of Release Testing upon product quality and lead times, we must heed the advice of W. Edwards Deming that “we cannot rely on mass inspection to improve quality“. Rather than try to inspect quality into each product increment, we must instead build quality in by replacing Release Testing with feedback-driven product development activities in which release testers become valuable members of the product team. By moving release testers into the product team everyone is able to collaborate in tight feedback loops, and the existing end-to-end tests can be assessed for removal, replacement, or retention. This will reduce both the wait waste and overprocessing waste in the value stream, empowering the team to focus upon valuable post-development activities such as automated smoke testing of environment configuration and the manual exploratory testing of product features.

Release Testing - Final Product Team

A far more effective risk reduction strategy than Release Testing is batch size reduction, which can attain a notable reduction in defect probability with a minimal transaction cost. Championed by Eric Ries asserting that “small batches reduce risk“, releasing smaller change sets into production more frequently decreases the complexity of each change set, therefore reducing both the probability and cost of defect occurrence. In addition, batch size reduction also improves overheads and product increment flow, which will produce a further improvement in lead times.

Release Testing is not the fault of any developer, or any tester. It is a systemic fault that causes blameless teams of individuals to be bedevilled by a sub-optimal organisational structure, that actively harms lead times and product quality in the name of risk management theatre. Ultimately, we need to embrace the inherent lessons of Agile software development and Continuous Delivery – product quality is the responsibility of everyone, and testing is an activity not a phase.

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