Test Strategies

Testing strategies no matter what area you wish to troubleshoot are based on the same techniques. Remember that when troubleshooting to follow these following steps;

Identify the symptoms of the problem – get the facts, ask
Identify the area affected – again get facts, ask
Identify any recently-applied changes
Identify the most likely source of the problem. At this stage you may wish to employ linear or half-split methods to assist in locating the source of the problem
Implement the solution
Test the solution
Analyse the possible effects of the solution
Document everything throughout the process

This example shown below is not concerned with computing, but shows that the troubleshooting techniques can be applied in many different areas.

Scenario: A new housing area is currently being built, and you are working as a member of the construction team. One day, when the heating technicians are on-site doing checks of the gas boilers in each new house, they report that the last house in the street does not have any gas coming into the house. The piping is installed, of course, but when they turn the gas valve on nothing comes out. The gas pipeline servicing these houses is laid out in the following manner:

Each black dot on the diagram is a shutoff valve, used for isolating different sections of the service pipeline. Based on the heating technician’s report, you conclude that the service pipeline going up to that house must not be “live” and that one of the numbered valves was probably left in the off position. But which one could it be?
You know that the main utility connection at the street is “live,” because the gas heater in the contractor mobile building is working just fine.

You decide to go to valve number 8 and check for gas pressure at that point in the pipeline with a portable pressure gauge, then checking the pressure at each valve location down the pipeline until you find where there is good gas pressure. However, before you step out of the room to go do this, one of your co-workers suggests you start your search at the middle point of the pipeline instead: at the location of valve.

Explain why your co-worker’s idea is better, and also what your next step would be if: (a) you did find pressure at that point, and (b) if you did not find pressure at that point.

Answer:

Your co-worker’s strategy is based on the principle of dividing the gas pipeline into halves, and checking for pressure at the half-way point. This troubleshooting strategy is sometimes referred to as the Half-Split or “divide-and-conquer” method, because it divides the system into small sections to optimise troubleshooting time and effort.

This problem gives you a chance to explore the “divide and conquer” strategy of troubleshooting in a context that is very simple and does not require knowledge of computing at all.

Next: Problem-Solving Tools