§ 4502. Spouse. (a) Incompetency where issue adultery. A husband or wife is not competent to testify against the other in an action founded upon adultery, except to prove the marriage, disprove the adultery, or disprove a defense after evidence has been introduced tending to prove such defense. (b) Confidential communication privileged. A husband or wife shall not be required, or, without consent of the other if living, allowed, to disclose a confidential communication made by one to the other during marriage.