What is the test for causation and damages in a medical malpractice action?

"With regard to causation and damages, the plaintiff is required to prove that but for the [attorney's] negligent acts or omissions, 'the plaintiff would have obtained a more favorable judgment or settlement in the action in which the malpractice allegedly occurred.' [Citations.] As such, a determination of the underlying case is required. This method of presenting a legal malpractice lawsuit is commonly called a trial within a trial. It may be complicated, but it avoids speculative and conjectural claims." (Blanks v. Seyfarth Shaw LLP (2009) 171 Cal.App.4th 336, 357.)