feat: add unit tests to SearchServiceTests

[alter-kaker]

• add testSearchPostByUrlReturnsEmptyWhenNoPosts - fails, disabled
• add testSearchPostByUrlWithCrossPostsFewerPostsThanPageSize - fails, disabled
• add testSearchPostByUrlWithCrossPostsOnePageWorthOfPostsRequestSecondPage - fails, disabled
• rename testSearchPostByUrlWithCrossPostsReturnsExactlyOnePageWorthOfResults - passes
• add testSearchPostByUrlWithCrossPostsPageOneOfTwo - passes
• add testSearchPostByUrlWithCrossPostsPageTwoOfTwo - passes

closes #407

[lazyguru]

Also, @alter-kaker would you be able to configure your git client to sign your commits?