title: How mock a test for EntityManager.transaction() in TypeOrm?
body: <p>I have this function in my controller:</p>
  <pre><code>async save(req: Request, res: Response) {
      try {            
          const user = new User();
          user.nome = 'Jhon Doe';
          
          const admin = new Morador;
          admin.user = user;
          
          await getManager().transaction( async entity =&gt; {
              await entity.save(user);
              await entity.save(admin);
          });
  
          res.status(201).json(admin);
  
      } catch (e) {
          res.sendStatus(500);
      }
  }
  </code></pre>
  <p>I need to mock this function:</p>
  <pre><code>await getManager().transaction( async entity =&gt; {
      await entity.save(user);
      await entity.save(admin);
  });
  </code></pre>
  <p>I need to receive the input values from the <code>entity.save</code> function.
  How to do this with Jest?</p>