public static MockAddressResolverGroup of(Function<String, InetAddress> resolver) {
        return new MockAddressResolverGroup(requireNonNull(resolver, "resolver"));
    }
Creates an {@link AddressResolverGroup} which resolves a given hostname to an {@link InetAddress}
using the specified {@code resolver}.
testing-internal/src/main/java/com/linecorp/armeria/internal/testing/MockAddressResolverGroup.java