### Question:
CategorizationResultReducer implements AnalyzerResultReducer<CategorizationResult> { @Override public CategorizationResult reduce(final Collection<? extends CategorizationResult> results) { final RowAnnotationFactory annotationFactory = null; final Map<String, RowAnnotation> reducedCategories = new LinkedHashMap<>(); for (final CategorizationResult result : results) { final Collection<String> categoryNames = result.getCategoryNames(); for (final String categoryName : categoryNames) { final RowAnnotation partialAnnotation = result.getCategoryRowAnnotation(categoryName); final RowAnnotation reducedAnnotation = reducedCategories.get(categoryName); if (reducedAnnotation == null) { final RowAnnotation annotation = _rowAnnotationFactory.createAnnotation(); _rowAnnotationFactory.transferAnnotations(partialAnnotation, annotation); reducedCategories.put(categoryName, annotation); } else { _rowAnnotationFactory.transferAnnotations(partialAnnotation, reducedAnnotation); } } } return new CategorizationResult(annotationFactory, reducedCategories); }  @Override CategorizationResult reduce(final Collection<? extends CategorizationResult> results);  }### Answer:
@Test public void testReduceEmpty() throws Exception { final RowAnnotationFactory annotationFactory = new InMemoryRowAnnotationFactory2(4); final CategorizationResultReducer reducer = new CategorizationResultReducer(); reducer._rowAnnotationFactory = annotationFactory; final Map<String, RowAnnotation> categories1 = new LinkedHashMap<>(); final Map<String, RowAnnotation> categories2 = new LinkedHashMap<>(); final Map<String, RowAnnotation> categories3 = new LinkedHashMap<>(); final Collection<CategorizationResult> results = new ArrayList<>(); results.add(new CategorizationResult(annotationFactory, categories1)); results.add(new CategorizationResult(annotationFactory, categories2)); results.add(new CategorizationResult(annotationFactory, categories3)); final CategorizationResult reducedResult = reducer.reduce(results); assertEquals(0, reducedResult.getCategoryNames().size()); }
@Test public void testReduceTypicalScenario() throws Exception { final RowAnnotationFactory annotationFactory = new InMemoryRowAnnotationFactory2(4); final CategorizationResultReducer reducer = new CategorizationResultReducer(); reducer._rowAnnotationFactory = annotationFactory; final Map<String, RowAnnotation> categories1 = new LinkedHashMap<>(); categories1.put("Male", new RowAnnotationImpl(50)); categories1.put("Female", new RowAnnotationImpl(50)); final Map<String, RowAnnotation> categories2 = new LinkedHashMap<>(); categories2.put("Male", new RowAnnotationImpl(46)); categories2.put("Female", new RowAnnotationImpl(50)); categories2.put("Unknown", new RowAnnotationImpl(3)); final Map<String, RowAnnotation> categories3 = new LinkedHashMap<>(); categories3.put("Male", new RowAnnotationImpl(27)); categories3.put("Female", new RowAnnotationImpl(24)); final Collection<CategorizationResult> results = new ArrayList<>(); results.add(new CategorizationResult(annotationFactory, categories1)); results.add(new CategorizationResult(annotationFactory, categories2)); results.add(new CategorizationResult(annotationFactory, categories3)); final CategorizationResult reducedResult = reducer.reduce(results); assertEquals(3, reducedResult.getCategoryNames().size()); assertEquals(123, reducedResult.getCategoryCount("Male")); assertEquals(124, reducedResult.getCategoryCount("Female")); assertEquals(3, reducedResult.getCategoryCount("Unknown")); }