private Map<Class<?>, UnaryOperator<?>> getMappers() {
        final Map<Class<?>, UnaryOperator<?>> combinedMap = new HashMap<>();
        combinedMap.putAll(STATIC_VALUE_MAPPERS);
        combinedMap.putAll(valueMappers);
        return combinedMap;
    }
Intercepts any calls to getConfigObject and allows the returned values to be replaced
with different values for testing.
stroom-app/src/test/java/stroom/test/ConfigMapperSpy.java