My wife just passed her US citizenship and will be sworn in March 14, 2019
The process, being married to a US citizen, was as follows:
1. Have to reside in the USA for 3 years minimum if married to a US Citizen (5 years if not)
2. After 3 years residence, you can send in the application for US citizenship (N-400 form along with the fee of US $725). We sent that in on (April 2018)
Somewhere in the process we received a test booklet for her to study. Can also download it from the immigration site.
3. Received Notice of Action form I-797C, which scheduled the immigration interview and test at the USCIS Immigration Center February 2019, (10 months after the application was sent it)
Although the letter tells you to bring a list of documents, her immigration officer did not look at any of them. Straight to the interview and test. That took about 30 minutes. There was an interview about being married, etc., oral test of questions from the test book about US Civics, and then the officer will read you something that you have to correctly write in English. Then they took her fingerprints (biometrics) to do one more police check. They let you know right then, before you leave, if you passed or not.
4. Just received the "swear in" letter a few days after the Interview (USCIS N-445) to go "swear in" March 14, 2019 at the Federal Court House in Orlando, Florida at which time it will be 100% official
5. The N-400 application gives your wife a chance to change her name legally which mine did. So after the "swear in" it will be name changing on drivers license, credit cards, et.c, etc., etc.