I think pair testing is not a technique, but an approach. An approach reflects a broad vision about the best way to organize your testing, rather than specific tactics for designing individual tests.
Testing, as I see it, is:
- In search of quality-related information
- Questioning the product in order to evaluate it and learn from it
- Gathering information to make an informed decision
These are the definitions of testing I work with. Testing is all about asking questions and collecting information. By asking questions, you learn more about the application you are testing, and while learning, you create more questions to reveal more information.
The earlier in the software development lifecycle you start testing, the more information you can collect, and the better you can design your tests. One way to start testing earlier is with two people working together on the same testing task, or pair testing.
Much like with pair programming, the biggest disadvantage is that two people are working on the same assignment. Managers will complain about that, saying they should be working on different things so that they can cover more of the application and that time and money are spent more wisely.
But are they? Working as a pair has its advantages. Let’s look at some of them and see if you can encourage your team to try pair testing.
Two Heads Are Better Than One
In pair testing, generally one person is executing the tests while the other person is making notes of what has been done and what has been observed, in order to inform the testers and the stakeholders. When needed, they can switch. What you have here is two different minds and two sets of eyes focused on the assignment. One person observes and asks, the other person thinks and responds, and both people inspire each other.
This exercise is useful to come up with test ideas. The pair can then agree on decisions and divide the work. When you work alone, you constantly switch between test execution and making notes of your observations, so working as a team will make you go faster.
Increased Coverage of Knowledge
As two people are working together on the same assignment, they will grow to the same level of knowledge about the application. That way, there is no single point of failure because the knowledge is shared.
There’s also the advantage that if one person is not able to participate, the other one can take over, and the work on the application is not interrupted.
Likewise, when emergencies occur, such as a problem in the production environment, one person can look into the problem while the other continues with the test assignment. When the problem is solved, they inform each other about what happened and continue their work as a pair. There is a quick alignment and easy knowledge transfer, and the specifics of the application are always covered.
In some situations, there is a clear distinction between roles in pair testing. The pair can consist of a junior and a senior tester, with the senior tester acting as a mentor, teaching the junior. The junior executes the test as the senior observes and guides, from time to time asking clarifying questions to ensure the junior understands what they’re doing.
This also works for introducing a new colleague to the application. A new tester can be paired with a subject matter expert to observe testing, with the subject matter expert explaining how the application works and what it can do. The new colleague can ask questions and be sure they understand the product before working on their own.
I currently work on a Scrum team as the only tester. When it is my team's turn to execute the regression testing of the application, I visit my colleague testers on other teams to see if the features they worked on are part of the regression test. If so, we do some pair testing together to transfer knowledge, so I can learn how the features are supposed to work.
Better Bug Investigation
Sometimes you run into a problem that is hard to investigate. You see some weird behavior in the application under test, but you can’t figure out what is wrong.
Help can come from another tester, a business analyst, a solution designer, or even a developer. Together you replay the error scenario and investigate the problem, then test with other input or data to see if there are more problems, which can result in a bug report. You may not have thought about it, but this is actually pair testing.
Once I was testing a feature and could not execute a request to the back-end system. I asked the tester who worked on that feature to help me. While testing, we found out that there was a serious issue with the back end. They forgot to implement an extra parameter while the front-end applicator was in a newly introduced state. By pairing, we were able to investigate and resolve the bug quicker and more thoroughly than I would have been able to by myself.
Thorough Test Preparation
Testing an application requires preparation, and working in a pair sets you up for success.
When working on test design as a pair, I recommend you read the documentation about the application separately, then have a brainstorm session together about what you read. Make a list with risks as you identify them, then create a mind map of areas to cover that are related to the identified risks. Together you can come up with questions to help you get more clarification on the risks and create test ideas to be executed to gather information.
The discussions you have will create a flow of thoughts you wouldn’t get when working alone.
A Way to Stay Focused
As a single tester, you can get easily distracted by your surroundings and lose focus from the work you’re supposed to do. When you are working as a pair, there is more focus on the assignment. If one person’s mind starts to wander, the other one will get them back on track.
Distractions also can be work-related, and when that happens, the distractions must be dealt with. Pairing can help in this situation, too. If you need to stop work in order to pay attention to an urgent problem, when you’re done and can return to the original assignment, your tester colleague can bring you up to speed with the latest activities and information.
Give Pair Testing a Try
Working as a pair does mean that there sometimes will be logistical issues. A simple example is that one person could start work early in the morning so they can leave early, but the other person may prefer working later hours.
This doesn’t have to throw off your pair testing, though. The early person can start with some preparation of the test ideas to be investigated. Then, they can work on the prepared ideas together. The late person can finish up by completing the test reports and filing the remaining bugs that have been found. No one has to be inconvenienced; it just requires some coordination.
Pair testing can be done with various disciplines within the software development lifecycle. It has many advantages, both for the quality of the product and the benefit of the testers, and it doesn’t require any special training. You only need two brains and two pairs of eyes. The rest will follow as you organize your work.