Resolve "Unit tests unter Windows"

Summary

100% tests passed, 0 tests failed out of 108

Related to #77 (closed) and #72 (closed)

Focus

Point the reviewer to the core of the code change. Where should they start reading? What should they focus on (e.g. security, performance, maintainability, user-friendliness, compliance with the specs, finding more corner cases, concrete questions)?

Test Environment

How to set up a test environment for manual testing?

Check List for the Author

Please, prepare your MR for a review. Be sure to write a summary and a focus and create gitlab comments for the reviewer. They should guide the reviewer through the changes, explain your changes and also point out open questions. For further good practices have a look at our review guidelines

• All automated tests pass
• Reference related issues
• Up-to-date CHANGELOG.md (or not necessary)
• Up-to-date JSON schema (or not necessary)
• Appropriate user and developer documentation (or not necessary)
  • How do I use the software? Assume "stupid" users.
  • How do I develop or debug the software? Assume novice developers.
• Annotations in code (Gitlab comments)
  • Intent of new code
  • Problems with old code
  • Why this implementation?

Check List for the Reviewer

• I understand the intent of this MR
• All automated tests pass
• Up-to-date CHANGELOG.md (or not necessary)
• Appropriate user and developer documentation (or not necessary)
• The test environment setup works and the intended behavior is reproducible in the test environment
• In-code documentation and comments are up-to-date.
• Check: Are there specifications? Are they satisfied?

For further good practices have a look at our review guidelines.

include/linkahead/connection.h

@@ -170,6 +170,9 @@ class ConnectionManager {
 private:
   mutable std::map<std::string, std::shared_ptr<Connection>> connections;
   mutable std::string default_connection_name;
+
+  static ConnectionManager mInstance;
+
   inline ConnectionManager(){};
 
   auto mHasConnection(const std::string &name) const -> bool;
@@ -184,10 +187,7 @@ private:
   }
 
 public:
-  static ConnectionManager &GetInstance() {
-    static ConnectionManager instance;
-    return instance;
-  };
+  static ConnectionManager &GetInstance();
 
   inline static auto HasConnection(const std::string &name) -> bool {
     return ConnectionManager::GetInstance().mHasConnection(name);