S getSerde() {
        // serde is kept for the life of the test
        if (serde == null) {
            serde = getSerdeSupplier().get();
        }
        return serde;
    }
Assumes a no-arg ctor, override if serde doesn't have one.
stroom-lmdb/src/test/java/stroom/lmdb/serde/AbstractSerdeTest.java