public S getShared() {
    if (theSharedInstance == null) {
      throw new SharedContextException();
    }
    return (S) theSharedInstance;
  }
Returns the Shared Test Instance
<p>
If accessed, the Specification will run and initialize the shared instance before this can be evaluated.

@since 2.1
@return the shared instance
spock-core/src/main/java/org/spockframework/runtime/extension/builtin/PreconditionContext.java