allow running all tests at the same path by invalidating all cached realm paths between test runs

shared_realm.cpp

@@ -198,7 +198,9 @@ bool Realm::update_schema(std::unique_ptr<Schema> schema, uint64_t version)
     auto migration_function = [&](Group*,  Schema&) {
         SharedRealm old_realm(new Realm(old_config));
         auto updated_realm = shared_from_this();
-        m_config.migration_function(old_realm, updated_realm);
+        if (m_config.migration_function) {
+            m_config.migration_function(old_realm, updated_realm);
+        }
     };
 
     try {
@@ -438,6 +440,19 @@ void RealmCache::cache_realm(SharedRealm &realm, std::thread::id thread_id)
     }
 }
 
+void RealmCache::invalidate_all()
+{
+    std::lock_guard<std::mutex> lock(m_mutex);
+
+    for (auto &path_realms:m_cache) {
+        for (auto &realm_iter:path_realms.second) {
+            if (auto realm = realm_iter.second.lock()) {
+                realm->invalidate();
+            }
+        }
+    }
+}
+
 void RealmCache::clear()
 {
     std::lock_guard<std::mutex> lock(m_mutex);

shared_realm.hpp

@@ -131,6 +131,7 @@ namespace realm {
         SharedRealm get_any_realm(const std::string &path);
         void remove(const std::string &path, std::thread::id thread_id);
         void cache_realm(SharedRealm &realm, std::thread::id thread_id = std::this_thread::get_id());
+        void invalidate_all();
         void clear();
 
       private: