Integration testing

Hi all,
I am new to ETL testing and have some doubts which i want to post here. Kindly excuse any errors made by me.

1. How do we test data which has cardinal mappings between fields. Say for instance, the fields present in Source file are mapped to diferent fields in diferent source files. When data in dropped through ETL in ODS or a datamart, how do we test the data and mapping. For example, we have files with Customer information, which have more than one account, loan account. The account is a joint account and this information resides in diferent source files. How do we verify them.

2. There is change in one of field mapping or data rule and it is fixed. We will test the changed field's data, but How do we regression test tables or fields which have not changed, to make sure our fix doesnt change anything else.

I am afraid I dont have specifics as to fields or files. I would greatly appreciate if the forum provides any inputs here.

Thanks,
Pallavi

ETL testing is no different from testing any other type of system - regarding the point you raised:

1. Identify every use case, create test data for each one and then load it e.g. for each target field identify the source(s) for it, create the source data and load it. Where there are multiple sources ensure that you load them in every possible timing combination such as Source 1 then Source 2, Source 2 then Source 1, etc.

2. You regression test ETL in the same way you regression test any other system: you have a standard source data set, you have a documented target data set and then you load your source data and ensure the result matches your documented target data set.

Regards