Selecting a test strategy for regression testing

Regression testing is selective retesting of the system; executed with an objective to ensure the bug fixes work and those bug fixes have not caused any un-intended effects in the system.
The selection of test cases for regression testing depends on:
- Requires knowledge on the bug fixes and how it affect the system.
- Includes the area of frequent defects.
- Includes the area which has undergone many/recent code changes.
- Includes the area which is highly visible to the users.
- Includes the core features of the product which are mandatory requirements of the customer.
Selection of test cases for regression testing depends more on the criticality of bug fixes than the criticality of the defect itself.
Do not focus on the test cases that are bound to fail and those test cases which has no or less relevance to the bug fixes. Select more positive test cases than negative test cases for final regression test cycle as this may create some confusion and unexpected heat. It is also recommended that the regular test cycles before regression testing should have right mix of both positive and negative test cases. Negative test cases are those test cases which are introduced newly with intent to break the system.

Good approach is to plan and act for regression testing from the beginning of project before the test cycles. One of the ideas is to classify the test cases into various Priorities based on importance and customer usage.

For an Effective Regression Testing :
- Create a regression test plan identifying focus areas, strategy, test entry and exit criteria. It can also outline Testing Prerequisites, Responsibilities, etc.
- Create test cases.
- Defect tracking.