Improve the test suite

[grisu48]

The test suite is far from being complete. This issue is about tracking the progress of increasing the test coverage, which is crucial for a reliable library.

[grisu48]

https://github.com/grisu48/gopenqa/pull/6 improves the coverage of fetching jobs.

[grisu48]

https://github.com/grisu48/gopenqa/pull/9 adds machines and products to the testsuite