Yes, under the North Carolina codes, the wife can testify on behalf of the prosecution in assault cases where the spouse is the criminal defendant. Below is the code section, it is one of limited circumstances where the wife can testify on behalf of the prosecution.
If the wife refuses to testify, she will be in Contempt of Court which could mean possible jail time or fines for violating the Subpoena.

§ 8-57. Husband and wife as witnesses in criminal actions.

(a) The spouse of the defendant shall be a competent witness for the defendant in all criminal actions, but the failure of the defendant to call such spouse as a witness shall not be used against him. Such spouse is subject to cross-examination as are other witnesses.

(b) The spouse of the defendant shall be competent but not compellable to testify for the State against the defendant in any criminal action or Grand Jury proceedings, except that the spouse of the defendant shall be both competent and compellable to so testify:

(1) In a prosecution for Bigamy or criminal cohabitation, to prove the fact of marriage and facts tending to show the absence of divorce or annulment;

(2) In a prosecution for assaulting or communicating a threat to the other spouse;

(3) In a prosecution for trespass in or upon the separate lands or residence of the other spouse when living separate and apart from each other by mutual consent or court order;

(4) In a prosecution for Abandonment of or failure to provide support for the other spouse or their child;

(5) In a prosecution of one spouse for any other criminal offense against the minor child of either spouse, including any illegitimate or adopted or foster child of either spouse.

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