Challenge Summary

A common question from Test Case Designer clients in the early adoption stages is:

“Before, we had a clear testing focus for each scenario, so we knew exactly what would fail the test. Now, with all the inputs mixed together, how can we identify the cause of a defect?”

The purpose of this article is This article aims to demonstrate a defect analysis approach when using TCD tests. We’ll use a simplistic customer preferences application with 5 “Checked”/ ”Not Checked” indicators, looking like this:

Challenge Summary

Manually selected tests would likely focus on isolated scenarios:

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So, when test #3 fails, it tells us there is likely something wrong with Indicator 3.

If instead, we use Test Case Desgner Designer to generate the a set of 2-way tests for this application, ; we might get test scenarios like these:

Now, if If scenario #4 fails, it’s not just Indicator 3 that is checked, but also Indicator 1.

So, how do we pinpoint the reason for the failure?

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TCD Analysis Approach

The key to our analysis is to look at the whole test suite and identify the dependency pattern between the consistent elements and the execution outcome.

First, let’s define the “strength” of the defect. We’ll call an issue a “one-way defect” if it is caused by just a single parameter value, irrespective of everything else happening in the test case. A “two-way defect” means that a specific combination of 2 parameter values happening together triggers the error (e.g., Checked for Indicator 1 AND Checked for Indicator 4), and so on for “three-way defects” and beyond.

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If this is truly a 1-way defect of “Indicator 3 = Checked”, then the rest of the values in the row won’t matter. The same defect would be caught by each of the following highlighted TCD scenarios:

The debugging process, in this case, would consist of the following steps (assuming there is no error message specifying exactly what went wrong):

1. Execute all the scenarios and notice that scenarios #1, #4, and #6 were the only ones that failed.
2. Analyze what is the consistent element in each of these scenarios is:

• Indicator 1 has both values – not a culprit
• Indicator 2 has both values – not a culprit
• Indicator 3 has only “Checked” value – culprit
• Indicator 4 has both values – not a culprit
• Indicator 5 has both values – not a culprit

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So it’s important to use a combinatorial testing methodology to improve the testing coverage and then adjust the defect analysis process accordingly.

Achieving both isolated and combinatorial testing

There may be situations where targeted testing is absolutely necessary. Test Case Designer allows you to do this by forcing specific parameter values to be used. For example, we can force only 1 indicator at a time to be checked in each of the first 5 scenarios:

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