Add test for pipelines

[s3rius]

I'm not really sure how to test it, but we have to.

[caffeinatedgaze]

It looks like this is implemented.

[s3rius]

True. But it's not as much as I'd like.

[caffeinatedgaze]

Could you share what else would you like to see tested? (I may be able to help out)

[s3rius]

• tests for all steps with correct and incorrect parameters;
• tests for abort exception usage;

For now I see only these cases, because the lib is relatively small.