In this time, a man could accuse his wife and have her put to death based on his suspicions alone. In many of the cultures of this time, his wife was his property to dispose of as he wished. This was, perhaps, a baby step toward providing an innocent wife a chance to prove her innocence in a manner that the husband could not contend, and which ultimately placed judgment in God's hands.
There is a reason why our court system is based on the presumption of innocence. It's because in most cases it is impossible to prove that you did NOT do something. The best one can hope for is to interject reasonable doubt that you are guilty.
In the context of the time, this "adultery test" was an improvement in the circumstances of women. It allowed God to be the ultimate judge of her character, rather than a jealous husband. For us today, it is a reminder that God knows our guilt or innocence. Jesus is our faithful bridegroom. He not only provides the offering to atone for our sin, He drank the cup of God's wrath so that we, the unfaithful bride, would not have to.