Module: Minitest::AssertChanges

Included in:
Test
Defined in:
lib/minitest/assert_changes.rb,
lib/minitest/assert_changes/version.rb

Constant Summary collapse

UNTRACKED =

:nodoc:

Object.new
VERSION = 
"1.0.0"

Instance Method Summary collapse

Instance Method Details

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

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



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# File 'lib/minitest/assert_changes.rb', line 41

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

  retval
end

#assert_no_changes(expression, message = nil, &block) ⇒ Object

Assertion that the result of evaluating an expression is 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



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# File 'lib/minitest/assert_changes.rb', line 80

def assert_no_changes(expression, message = nil, &block)
  exp = expression.respond_to?(:call) ? expression : -> { eval(expression.to_s, block.binding) }

  before = exp.call
  retval = yield
  after = exp.call

  error = "#{expression.inspect} did change to #{after}"
  error = "#{message}.\n#{error}" if message
  assert_equal before, after, error

  retval
end