SeriesServiceImpl.replaceImage(): add unit tests

[0pdd]

The puzzle 1303-7c7e06c0 from #1303 has to be resolved:

mystamps/src/main/java/ru/mystamps/web/feature/series/SeriesServiceImpl.java

Line 143 in 4c2104a

// @todo #1303 SeriesServiceImpl.replaceImage(): add unit tests

The puzzle was created by Slava Semushin on 28-Apr-20.