Minitest Assertions

#ruby #rails #testing #webdev

Ruby on Rails 7 ships with Minitest. Here's a definitive guide to what assertions are available in Minitest 5.1.

Assertion	Asserts
`assert( test, [msg] )`	Asserts that `test` is true.
`assert_not( test, [msg] )`	Asserts that `test` is false.
`assert_equal( expected, actual, [msg] )`	Asserts that `expected == actual` is true.
`assert_not_equal( expected, actual, [msg] )`	Asserts that `expected != actual` is true.
`assert_same( expected, actual, [msg] )`	Asserts that `expected.equal?(actual)` is true.
`assert_not_same( expected, actual, [msg] )`	Asserts that `expected.equal?(actual)` is false.
`assert_nil( obj, [msg] )`	Asserts that `obj.nil?` is true.
`assert_not_nil( obj, [msg] )`	Asserts that `obj.nil?` is false.
`assert_empty( obj, [msg] )`	Asserts that `obj` is `empty?`.
`assert_not_empty( obj, [msg] )`	Asserts that `obj` is not `empty?`.
`assert_match( regexp, string, [msg] )`	Asserts that a string matches the regular expression.
`assert_no_match( regexp, string, [msg] )`	Asserts that a string doesn't match the regular expression.
`assert_includes( collection, obj, [msg] )`	Asserts that `obj` is in `collection`.
`assert_not_includes( collection, obj, [msg] )`	Asserts that `obj` is not in `collection`.
`assert_in_delta( expected, actual, [delta], [msg] )`	Asserts that the numbers `expected` and `actual` are within `delta` of each other.
`assert_not_in_delta( expected, actual, [delta], [msg] )`	Asserts that the numbers `expected` and `actual` are not within `delta` of each other.
`assert_in_epsilon ( expected, actual, [epsilon], [msg] )`	Asserts that the numbers `expected` and `actual` have a relative error less than `epsilon`.
`assert_not_in_epsilon ( expected, actual, [epsilon], [msg] )`	Asserts that the numbers `expected` and `actual` have a relative error not less than `epsilon`.
`assert_throws( symbol, [msg] ) { block }`	Asserts that the given block throws the symbol.
`assert_raises( exception1, exception2, ... ) { block }`	Asserts that the given block raises one of the given exceptions.
`assert_instance_of( class, obj, [msg] )`	Asserts that `obj` is an instance of `class`.
`assert_not_instance_of( class, obj, [msg] )`	Asserts that `obj` is not an instance of `class`.
`assert_kind_of( class, obj, [msg] )`	Asserts that `obj` is an instance of `class` or is descending from it.
`assert_not_kind_of( class, obj, [msg] )`	Asserts that `obj` is not an instance of `class` and is not descending from it.
`assert_respond_to( obj, symbol, [msg] )`	Asserts that `obj` responds to `symbol`.
`assert_not_respond_to( obj, symbol, [msg] )`	Asserts that `obj` does not respond to `symbol`.
`assert_operator( obj1, operator, [obj2], [msg] )`	Asserts that `obj1.operator(obj2)` is true.
`assert_not_operator( obj1, operator, [obj2], [msg] )`	Asserts that `obj1.operator(obj2)` is false.
`assert_predicate ( obj, predicate, [msg] )`	Asserts that `obj.predicate` is true, e.g. `assert_predicate str, :empty?`
`assert_not_predicate ( obj, predicate, [msg] )`	Asserts that `obj.predicate` is false, e.g. `assert_not_predicate str, :empty?`
`assert_error_reported(class) { block }`	Asserts that the error class has been reported, e.g. `assert_error_reported IOError { Rails.error.report(IOError.new("Oops")) }`
`assert_no_error_reported { block }`	Asserts that no errors have been reported, e.g. `assert_no_error_reported { perform_service }`
`flunk( [msg] )`	Asserts failure. This is useful to explicitly mark a test that isn't finished yet.