Test coverage of switch when using an enum

Question

I'm writing a unit test for the following: -
switch (status) {
    case ACTIVE:
        return "A";
    case POSTED:
        return "P";
    default:
        throw new IllegalArgumentException("unknown status: " + status);
}Where status variable is an enum type like: -
public enum BatchStatus {
    ACTIVE, POSTED
}I'm of the opinion that having the default branch above makes the code safer and more robust (it means that if the enum grows, problems can be immediately identified).
So the question is... is it impossible to achieve 100% test coverage, but still retain the default branch above? Since the BatchStatus is an enum (and hence final, and cannot be instantiated), I can't create a third mock value that is neither ACTIVE nor POSTED, so I can't test the default branch.
???

Answer 1

rather than use the switch block - which isn't very OO, and is a maintenance pain - why not have the enum itself return these values?
public enum BatchStatus {
ACTIVE("A"),
POSTED("P");
private BatchStatus(String status) {
    this.status = status;
private String status;
public String getStatus() {
    return this.status;
}that way, the maintenance programmers have no option but to keep the lot up to date. this over-simplified example probably doesn't address your real problem, but it might point you in a direction you hadn't considered before