Enterprise Library Test Guide - Willy .Net

Testing for Performance and
Scalability
Testing the Enterprise Library application blocks for performance and scalability
involves testing the library’s set of application blocks under both normal and peak
loads. The tests are performed without incorporating the application blocks into a
full-fledged application. The goals of the performance tests are:
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To verify that the application blocks meet the performance requirements while
staying within the budgeted constraints on system resources. The performance
requirements can include different measurements, such as the time it takes to
complete a particular scenario (this is known as the response time) or the number
of concurrent or simultaneous requests that can be satisfied for a particular operation
within a given response time. Examples of system resources are CPU time,
memory, disk I/O, and network I/O.
To analyze the behavior of the application blocks at various load levels. Performance
tests that measure this behavior use metrics that relate to the performance
objectives and other metrics that help to identify the bottlenecks in the application
blocks. A bottleneck is the device or resource that constrains throughput. Most of
the time, performance bottlenecks in your application relate to resource issues that
may include server resources, such as CPU, memory, disk I/O, and network I/O
or other external resources, such as available database connections or network
bandwidth. Bottlenecks can be caused by various issues, such as memory leaks,
slow response times, and contention for resources while under load.
Performance tests for the application blocks fall into two broad categories:
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Load tests. Load tests monitor and analyze the behavior of an application block
under both normal and peak load conditions. Load tests enable you to verify that
the application block meets the performance objectives.
Stress tests. Stress tests identify problems that occur both when the application
block operates under heavy load conditions and when it must operate under these
conditions for lengthy periods of time. The application block may fail under these
conditions because it has depleted some system resources. Another goal of stress
testing is to see if the application block can recover when its load exceeds the
specified limits and then returns to normal. In short, when you run stress tests,
monitor the application block to see if its performance degrades under heavy
loads and to see if its performance recovers after the load returns to normal.