When {pattern} does not match {actual} an error message is added to v:errors. Also see assert-return. The error is in the form "Pattern {pattern} does not match {actual}". When {msg} is present it is prefixed to that.

{pattern} is used as with =~: The matching is always done like 'magic' was set and 'cpoptions' is empty, no matter what the actual value of 'magic' or 'cpoptions' is.

{actual} is used as a string, automatic conversion applies. Use "^" and "$" to match with the start and end of the text. Use both to match the whole text.

Example:

assert_match('^f.*o$', 'foobar')

Will result in a string to be added to v:errors: test.vim line 12: Pattern '^f.*o$' does not match 'foobar'

Can also be used as a method:

getFile()->assert_match('foo.*')