Better sample source/rate init for tests.
Better sample source/rate init for tests.

appneta/ruby-traceview,tlunter/oboe-ruby,boyang-li/oboe-ruby,boyang-li/oboe-ruby,tlunter/oboe-ruby,appneta/ruby-traceview,tlunter/oboe-ruby,appneta/ruby-traceview,appneta/ruby-traceview,boyang-li/oboe-ruby,boyang-li/oboe-ruby,tlunter/oboe-ruby