Equally yoked is the main test. Yoked together in faith of God through your Lord Jesus. Remember you will be heirs together of heavenly riches.

Example tests of being equally yoked:

Willing Worker: If you're not a willing worker, able to work, and experiencing work then you're not ready for marriage. Marriage takes work. In so many areas, marriage requires work. Adam was already established in his work by the time God gave Eve to him. Take a hint from that truth.

Remember how the father sent his servant to seek out a wife for his son. The test was whether the girl would put her self out to do what was necessary when only asked to do a little. Whether she would take it on her own initiative to do all that was necessary to meet the obvious needs.

A willing worker is a wonderful person to live around. Two of them together as a team can do wonders.

A person who can see real needs beyond what is directly shown to them.
A person who cares about other people.
Common Social Ideals
The father sent his servant back to his own home country to find a girl for his son. This avoids so many problems I couldn't list them all.
Different social ideas can cause terrible explosions in an other wise wonderful marriage.

By returning to the homeland for his bride there was assurance of common understanding on how to do many details of life:
Food choices and preparation,
Dress and appropriateness of dress (according to what opinion?)
Mannerisms and expressions,
language of words,
body,
emotions values and value systems, priorities, putting first things first.
What's right and what's wrong, taboos and do's and don'ts
Common understanding on goals and purposes and priorities of life
Common communication experience of words and mannerisms can greatly help to avoid misunderstandings.
Work ethics and goals and motivations of that work
Common vision on the purpose of it all
Similar backgrounds in money and love, food, exercise, entertainment etc

Could a Viking be happy married to a French noble lady?