### Question:
PersistenceManagerImpl implements PersistenceManager { @Nullable @Override public String getSessionId() { return sharedPreferences.getString(Key.SESSION_ID, null); } @VisibleForTesting  PersistenceManagerImpl(Context context); @Override void setSessionId(String sessionId); @Nullable @Override String getSessionId(); @Override void setSourceToken(String sourceToken); @Nullable @Override String getSourceToken(); @Override void clear(); @Override boolean checkedDeferredDeepLink(); @Override void updateCheckDeferredDeepLink(boolean checkedDeferredDeepLink);  }### Answer:
@Test public void getSessionId_returnValidSessionId() { when(sharedPreferences.getString(PersistenceManagerImpl.Key.SESSION_ID, null)) .thenReturn("valid_session_id"); String sessionId = persistenceManager.getSessionId(); assertEquals("valid_session_id", sessionId); }