Were there a UI to review, these might be helpful. Generally, the evidence of an SSIS package execution is an updated database or a file either of which contain the transformed information.
As an example of a transform, if the input contains a field named Color and the value is Red. After the SSIS package executes, a database table of Colors has a column named Hue and our value, Red, appears there. The SSIS package mapped the field Color to the column Hue.
The complexity can rise from there when a field value must be transformed (e.g., Ohio to OH), or multiple fields are combined (e.g., FirstName and LastName are combined to Name). The SSIS package performs these transformations.
I can compare inputs and outputs but I’d like a method to isolate the complex transforms so the input/output comparison is simpler.