### Question:
RenderedFileCache extends AbstractFileCache<CombinedParams<W>> { @Override protected String getCacheFilename(CombinedParams<W> key) { return super.getCacheFilename(key) + '.' + key.getGraphviz().getOutputFormat().getFileExtension(); } RenderedFileCache(final File cacheDirectory, final int maxAgeInSeconds);   }### Answer:
@Test public void testgetCacheFilename() throws CacheException { VCatParams<TestWiki> vCatParams = new VCatParams<>(); GraphvizParams graphvizParams = new GraphvizParams(); graphvizParams.setOutputFormat(OutputFormat.PNG); CombinedParams<TestWiki> key = new CombinedParams<>(vCatParams, graphvizParams); final String result = underTest.getCacheFilename(key); assertTrue(result.endsWith('.' + OutputFormat.PNG.getFileExtension())); }