method

assert_changes

v5.1.7 - Show latest stable - 0 notes - Class: ActiveSupport::Testing::Assertions

1.0.0
1.1.6
1.2.6
2.0.3
2.1.0
2.2.1
2.3.8
3.0.0
3.0.9
3.1.0
3.2.1
3.2.8
3.2.13
4.0.2
4.1.8
4.2.1
4.2.7
4.2.9
5.0.0.1
5.1.7 (0)
5.2.3 (0)
6.0.0 (0)
6.1.3.1 (0)
6.1.7.7 (0)
7.0.0 (0)
7.1.3.2 (38)
7.1.3.4 (0)
What's this?

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

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

Show source

# File activesupport/lib/active_support/testing/assertions.rb, line 143
      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 = yield

        unless from == UNTRACKED
          error = "#{expression.inspect} isn't #{from.inspect}"
          error = "#{message}.\n#{error}" if message
          assert from === before, error
        end

        after = exp.call

        if to == UNTRACKED
          error = "#{expression.inspect} didn't changed"
          error = "#{message}.\n#{error}" if message
          assert_not_equal before, after, error
        else
          error = "#{expression.inspect} didn't change to #{to}"
          error = "#{message}.\n#{error}" if message
          assert to === after, error
        end

        retval
      end

assert_changes

Related methods