【RSpec】validate_uniqueness_ofでテストが落ちるときの対処 - Qiita

Expected Employee to validate that :number is unique, but this could not be proved. After taking the given Employee, whose :number is ‹0›, and saving it as the existing record, then making a new Employee and setting its :number to ‹0› as well, the matcher expected the new Employee to be invalid, but it was valid instead. 解決法 This matcher works a bit differently than other matchers. As noted before