Methods

Instance Public methods

assert_changes(expression, message = nil, from: UNTRACKED, to: UNTRACKED, &block)

Assertion that the result of evaluating an expression is changed before and after invoking the passed in block.

assert_changes 'Status.all_good?' do
  post :create, params: { status: { ok: false } }
end

You can pass the block as a string to be evaluated in the context of the block. A lambda can be passed for the block as well.

assert_changes -> { Status.all_good? } do
  post :create, params: { status: { ok: false } }
end

The assertion is useful to test side effects. The passed block can be anything that can be converted to string with to_s.

assert_changes :@object do
  @object = 42
end

The keyword arguments :from and :to can be given to specify the expected initial value and the expected value after the block was executed.

assert_changes :@object, from: nil, to: :foo do
  @object = :foo
end

An error message can be specified.

assert_changes -> { Status.all_good? }, 'Expected the status to be bad' do
  post :create, params: { status: { incident: true } }
end
๐Ÿ“ Source code 
# File activesupport/lib/active_support/testing/assertions.rb, line 175
      def assert_changes(expression, message = nil, from: UNTRACKED, to: UNTRACKED, &block)
        exp = expression.respond_to?(:call) ? expression : -> { eval(expression.to_s, block.binding) }

        before = exp.call
        retval = assert_nothing_raised(&block)

        unless from == UNTRACKED
          error = "Expected change from #{from.inspect}"
          error = "#{message}.\n#{error}" if message
          assert from === before, error
        end

        after = exp.call

        error = "#{expression.inspect} didn't change"
        error = "#{error}. It was already #{to}" if before == to
        error = "#{message}.\n#{error}" if message
        refute_equal before, after, error

        unless to == UNTRACKED
          error = "Expected change to #{to}\n"
          error = "#{message}.\n#{error}" if message
          assert to === after, error
        end

        retval
      end
๐Ÿ”Ž See on GitHub

assert_difference(expression, *args, &block)

Test numeric difference between the return value of an expression as a result of what is evaluated in the yielded block.

assert_difference 'Article.count' do
  post :create, params: { article: {...} }
end

An arbitrary expression is passed in and evaluated.

assert_difference 'Article.last.comments(:reload).size' do
  post :create, params: { comment: {...} }
end

An arbitrary positive or negative difference can be specified. The default is 1.

assert_difference 'Article.count', -1 do
  post :delete, params: { id: ... }
end

An array of expressions can also be passed in and evaluated.

assert_difference [ 'Article.count', 'Post.count' ], 2 do
  post :create, params: { article: {...} }
end

A hash of expressions/numeric differences can also be passed in and evaluated.

assert_difference ->{ Article.count } => 1, ->{ Notification.count } => 2 do
  post :create, params: { article: {...} }
end

A lambda or a list of lambdas can be passed in and evaluated:

assert_difference ->{ Article.count }, 2 do
  post :create, params: { article: {...} }
end

assert_difference [->{ Article.count }, ->{ Post.count }], 2 do
  post :create, params: { article: {...} }
end

An error message can be specified.

assert_difference 'Article.count', -1, 'An Article should be destroyed' do
  post :delete, params: { id: ... }
end
๐Ÿ“ Source code 
# File activesupport/lib/active_support/testing/assertions.rb, line 86
      def assert_difference(expression, *args, &block)
        expressions =
          if expression.is_a?(Hash)
            message = args[0]
            expression
          else
            difference = args[0] || 1
            message = args[1]
            Array(expression).index_with(difference)
          end

        exps = expressions.keys.map { |e|
          e.respond_to?(:call) ? e : lambda { eval(e, block.binding) }
        }
        before = exps.map(&:call)

        retval = assert_nothing_raised(&block)

        expressions.zip(exps, before) do |(code, diff), exp, before_value|
          error  = "#{code.inspect} didn't change by #{diff}"
          error  = "#{message}.\n#{error}" if message
          assert_equal(before_value + diff, exp.call, error)
        end

        retval
      end
๐Ÿ”Ž See on GitHub

assert_no_changes(expression, message = nil, &block)

Assertion that the result of evaluating an expression is not changed before and after invoking the passed in block.

assert_no_changes 'Status.all_good?' do
  post :create, params: { status: { ok: true } }
end

An error message can be specified.

assert_no_changes -> { Status.all_good? }, 'Expected the status to be good' do
  post :create, params: { status: { ok: false } }
end
๐Ÿ“ Source code 
# File activesupport/lib/active_support/testing/assertions.rb, line 215
      def assert_no_changes(expression, message = nil, &block)
        exp = expression.respond_to?(:call) ? expression : -> { eval(expression.to_s, block.binding) }

        before = exp.call
        retval = assert_nothing_raised(&block)
        after = exp.call

        error = "#{expression.inspect} changed"
        error = "#{message}.\n#{error}" if message

        if before.nil?
          assert_nil after, error
        else
          assert_equal before, after, error
        end

        retval
      end
๐Ÿ”Ž See on GitHub

assert_no_difference(expression, message = nil, &block)

Assertion that the numeric result of evaluating an expression is not changed before and after invoking the passed in block.

assert_no_difference 'Article.count' do
  post :create, params: { article: invalid_attributes }
end

A lambda can be passed in and evaluated.

assert_no_difference -> { Article.count } do
  post :create, params: { article: invalid_attributes }
end

An error message can be specified.

assert_no_difference 'Article.count', 'An Article should not be created' do
  post :create, params: { article: invalid_attributes }
end

An array of expressions can also be passed in and evaluated.

assert_no_difference [ 'Article.count', -> { Post.count } ] do
  post :create, params: { article: invalid_attributes }
end
๐Ÿ“ Source code 
# File activesupport/lib/active_support/testing/assertions.rb, line 137
      def assert_no_difference(expression, message = nil, &block)
        assert_difference expression, 0, message, &block
      end
๐Ÿ”Ž See on GitHub

assert_not(object, message = nil)

Asserts that an expression is not truthy. Passes if object is nil or false. โ€œTruthyโ€ means โ€œconsidered true in a conditionalโ€ like if foo.

assert_not nil    # => true
assert_not false  # => true
assert_not 'foo'  # => Expected "foo" to be nil or false

An error message can be specified.

assert_not foo, 'foo should be false'
๐Ÿ“ Source code 
# File activesupport/lib/active_support/testing/assertions.rb, line 21
      def assert_not(object, message = nil)
        message ||= "Expected #{mu_pp(object)} to be nil or false"
        assert !object, message
      end
๐Ÿ”Ž See on GitHub

assert_nothing_raised()

Assertion that the block should not raise an exception.

Passes if evaluated code in the yielded block raises no exception.

assert_nothing_raised do
  perform_service(param: 'no_exception')
end
๐Ÿ“ Source code 
# File activesupport/lib/active_support/testing/assertions.rb, line 33
      def assert_nothing_raised
        yield
      rescue => error
        raise Minitest::UnexpectedError.new(error)
      end
๐Ÿ”Ž See on GitHub