Data Migration Part 3 of 4

Test Scenarios, in general, would be as below:

I)​ If the migration is to the same type of Database, then,

  • Verify if the queries executed in the new database yield same results as in the older one
  • Verify if the number of records in the old database and new database is the same. Here use appropriate automation tool
  • Verify that there are no redundancies and new database works exactly as the older one
  • Verify if the schema, relationships, table structures are unaltered or set back to match the old database image
  • Verify whether the changes made in application updates new database with correct values and type
  • Verify if after the new database connection is provided to all the components of the application. Application, server, interfaces, firewall, network connectivity etc.
  • Verify the query performance (time-taken to execute complex queries) of the new database is not more than earlier performance

Challenges faced in this testing are mainly with data. Below are few in the list:

#1) Data Quality:

We may find that the data used in the legacy application is of poor quality in the new/upgraded application. In such cases, data quality has to be improved to meet business standards.

Factors like assumptions, data conversions after migrations, data entered in the legacy application itself are invalid, poor data analysis etc. leads to poor data quality. This results in high operational costs, increased data integration risks, and deviation from the purpose of business.

#2) Data Mismatch:

Data migrated from the legacy to the new/upgraded application may be found mismatching in the new one. This may be due to the change in data type, format of data storage, the purpose for which the data is being used may be redefined.

This result in huge effort to modify the necessary changes to either correct the mismatched data or accept it and tweak to that purpose.

#3) Data Loss:

Data might be lost while migrating from the legacy to the new/upgraded application. This may be with mandatory fields or non-mandatory fields. If the data lost is for non-mandatory fields, then the record for it will still be valid and can be updated again.

But if the mandatory field’s data is lost, then the record itself becomes void and it cannot be retracted. This will result in huge data loss and should have to be retrieved either from the backup database or audit logs if captured correctly.

#4) Data Volume:

Huge Data that requires a lot of time to migrate within the downtime window of the migration activity. ​E.g:​ Scratch cards in Telecom industry, users on an Intelligent network platform etc., here the challenge is by the time, the legacy data is cleared, a huge new data will be created, which needs to be migrated again. Automation is the solution for huge data migration.

#5) Simulation of a real-time environment (with the actual data):

Simulation of a real-time environment​ ​in the testing lab is another real challenge, where testers get into different kind of issues with the real data and the real system, which is not faced during testing.

So, data sampling, replication of real environment, identification of volume of data involved in migration is quite important while carrying out data Migration Testing.

#6) Simulation of the volume of data:

Teams need to study the data in the live system very carefully and should come up with the typical analysis and sampling of the data.

E.g:​ users with age group below 10 years, 10-30 years etc., As far as possible, data from the live needs to be obtained, if not data creation needs to be done in the testing environment. Automated tools need to be used to create a large volume of data. Extrapolation, wherever applicable can be used, if the volume cannot be simulated.


Data Migration Testing Part 2 of 4

Verification Requirements in the Migrated Environment: 

It is highly important to have a verification process built in for a migration testing process. By putting out the 

The following tests are designed for a hypothetical test case. 

  • Check whether all the data in the legacy is migrated to the new application within the downtime that was planned. To ensure this, compare the number of records between legacy and the new application for each table and views in the database. Also, report the time taken to move say 10000 records.
  • Check whether all the schema changes (fields and tables added or removed) as per the new system are updated.
  • Data migrated from the legacy to new application should retain its value and format unless it is not specified to do so. To ensure this, compare data values between legacy and new application’s database.
  • Test the migrated data against the new application. Here cover a maximum number of possible cases. To ensure 100% coverage with respect to data migration verification, use the automated testing tool.
  • Check for database security.
  • Check for data integrity for all possible sample records.
  • Check and ensure that the earlier supported functionality in the legacy system works as expected in the new system.
  • Check the data flow within the application which covers most of the components.
  • The interface between the components should be extensively tested, as the data should not be modified, lost, and corrupted when it is going through components. Integration test cases can be used to verify this.
  • Check for legacy data redundancy. No legacy data should be duplicated itself during migration
  • Check for data mismatch cases like data type changed, storing format is changed etc.,
  • All the field level checks in the legacy application should be covered in the new application as well
  • Any data addition in the new application should not reflect back on the legacy
  • Updating legacy application’s data through the new application should be supported. Once updated in the new application, it should not reflect back on the legacy.
  • Deleting the legacy application’s data in the new application should be supported. Once deleted in the new application, it should not delete data in legacy as well.
  • Verify that the changes made to the legacy system support the new functionality delivered as a part of the new system.
  • Verify the users from the legacy system can continue to use both the old functionality and new functionality, especially the ones where the changes are involved. Execute the test cases and the test results stored during the Pre-migration testing.
  • Create new users on the system and carry out tests to ensure that functionality from the legacy as well as the new application, supports the newly created users and it works fine.
  • Carry out functionality related tests with a variety of data samples (different age group, users from different region etc.,)
  • It is also required to verify if ‘Feature Flags’ are enabled for the new features and switching it on/off enables the features to turn on and off.
  • Performance testing is important to ensure that migration to new system/software has not degraded the performance of the system.
  • It is also required to carry out Load and stress tests to ensure the system stability.
  • Verify that the software upgrade has not opened up any security vulnerabilities and hence carry out security testing, especially in the area where changes have been made to the system during migration.
  • Usability is another aspect which is to be verified, wherein if GUI layout/front-end system has changed or any functionality has changed, what is the Ease of Use that the end user is feeling as compared to the legacy system.

Since the scope of Post-Migration testing becomes large, it is ideal to segregate the important tests that need to be done first to qualify that Migration is successful and then carry out the remaining later.

It is also advisable to automate the end to end functional test cases and other possible test cases so that the testing time can be reduced and the results would be available quickly.