ISTQB Glossary definition
"The degree to which a component or system is operational and accessible when required for use. Often expressed as a percentage."
In Simple English,
This is a simple measure of how much a system is available for users to use.
In testing usually this is read as how much time a system is available for testers to test the system.
Field Notes
- Most often it is expressed in percentage.
- Percentage is calculated as how much was the system available divided by how much was it expected to be available.
- It can also be expressed in just plain simple numbers. Say for example, The test site was available only 2 hours today"
- A tricky thing about availability is that it is always not clear what qualifies a site or system as available. what if the URL works and opens the site to be tested but the site is so slow that each step takes 45 seconds for the website to react.
- To avoid such situations, it is better to have the project and test phase specific definition of availability in the test plan document.
- Note that the availability measure does not change with the number of people to who it was not available.
- Note that the availability measure does not change with the number of times the site was not available either. sometimes this must be handled separately. Imagine what if the site was available for 5 minutes and then not available for another 5 minutes and then available again for just another 5 minutes all through the day repeating the cycle. In this case the site's availability mathematically would be 50%. How ever that does not convey the whole picture as essentially the site is as good as totally not available for testing as very little testing can be achieved in 5 minute cycles.
For Example:
For example, say you are testing a website. Your team of 12 people had planned to test this website 10 hours today. When the test day started the website was available. After an hour the website becomes unavailable. The URL does not open at all. so you suspend testing and would report that the website's availability was 10% during the test day.
For example, say you are testing a website. Your team of 12 people had planned to test this website 10 hours today. When the test day started the website was available. After an hour the website becomes unavailable. The URL does not open at all. so you suspend testing and would report that the website's availability was 10% during the test day.
- 10 % availability = (1 hour available /10 hours expected availability) * 100
