OpcUaServer.IntegrationTests was 4F. Two distinct, previously-masked issues:
1. Cert-store gap: the in-test client SecurityConfiguration used a bare
new SecurityConfiguration()/CertificateIdentifier(), so ValidateAsync threw
'TrustedIssuerCertificates StorePath must be specified' before any connect.
Added TestClientSecurity helper building Directory own/issuer/trusted/rejected
stores under a throwaway temp PKI dir (mirrors DefaultApplicationConfigurationFactory);
wired into DualEndpointTests + SubscriptionSurvivalTests.
2. Fixing #1 unmasked an SDK-version drift: the 1.5.378 node-cache read path
throws ServiceResultException(BadNodeIdUnknown) for a removed node instead of
returning a bad DataValue. The two subscription-survival assertions now expect
the throw via Should.ThrowAsync. Behavior under test (removed node -> unknown)
is unchanged; only the delivery mechanism differs.
Suite 4F -> 4/4 green. Integration-sweep follow-up #5.
Joseph Doherty