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方法
A

实例公共方法

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

断言在调用传递的块之前和之后，评估表达式的结果发生了变化。

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

您可以将块作为字符串传递，以便在块的上下文中进行评估。也可以将 lambda 传递给块。

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

断言对于测试副作用很有用。传递的块可以是任何可以转换为字符串的 to_s。

assert_changes :@object do
  @object = 42
end

关键字参数 :from 和 :to 可以用来指定预期的初始值和块执行后的预期值。

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

可以指定错误消息。

assert_changes -> { Status.all_good? }, 'Expected the status to be bad' do
  post :create, params: { status: { incident: true } }
end

来源：显示 | 在 GitHub 上 

# File activesupport/lib/active_support/testing/assertions.rb, line 191
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_or_warn("assert_changes", &block)

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

  retval
end

assert_difference(expression, *args, &block)

测试表达式返回值的数值差异，作为在 yield 块中评估的结果。

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

传递并评估一个任意表达式。

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

可以指定任意正或负差异。默认值为 1。

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

也可以传递并评估表达式数组。

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

也可以传递并评估表达式/数值差异的哈希。

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

可以传递并评估 lambda 或 lambda 列表

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

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

可以指定错误消息。

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

来源：显示 | 在 GitHub 上 

# File activesupport/lib/active_support/testing/assertions.rb, line 101
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_or_warn("assert_difference", &block)

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

  retval
end

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

断言在调用传递的代码块之前和之后，表达式求值的结果没有改变。

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

提供可选的关键字参数:from来指定预期的初始值。

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

可以指定错误消息。

assert_no_changes -> { Status.all_good? }, 'Expected the status to be good' do
  post :create, params: { status: { ok: false } }
end

来源：显示 | 在 GitHub 上 

# File activesupport/lib/active_support/testing/assertions.rb, line 238
def assert_no_changes(expression, message = nil, from: UNTRACKED, &block)
  exp = expression.respond_to?(:call) ? expression : -> { eval(expression.to_s, block.binding) }

  before = exp.call
  retval = _assert_nothing_raised_or_warn("assert_no_changes", &block)

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

  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

assert_no_difference(expression, message = nil, &block)

断言在调用传递的代码块之前和之后，表达式求值的数值结果没有改变。

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

可以传递一个 lambda 并进行求值。

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

可以指定错误消息。

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

也可以传递并评估表达式数组。

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

来源：显示 | 在 GitHub 上 

# File activesupport/lib/active_support/testing/assertions.rb, line 153
def assert_no_difference(expression, message = nil, &block)
  assert_difference expression, 0, message, &block
end

assert_not(object, message = nil)

断言表达式不是真值。如果object为nil或false，则通过。 “真值”表示“在条件语句中被认为是真值”，例如if foo。

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

可以指定错误消息。

assert_not foo, 'foo should be false'

来源：显示 | 在 GitHub 上 

# 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

assert_nothing_raised()

断言代码块不应该抛出异常。

如果在传递的代码块中执行的代码没有抛出异常，则通过。

assert_nothing_raised do
  perform_service(param: 'no_exception')
end

来源：显示 | 在 GitHub 上 

# File activesupport/lib/active_support/testing/assertions.rb, line 48
def assert_nothing_raised
  yield.tap { assert(true) }
rescue => error
  raise Minitest::UnexpectedError.new(error)
end

assert_raise(*exp, match: nil, &block)

别名：assert_raises

assert_raises(*exp, match: nil, &block)

断言一个代码块会抛出 exp 中的一个异常。这是对标准 Minitest 断言方法的增强，它能够测试错误消息。

assert_raises(ArgumentError, match: /incorrect param/i) do
  perform_service(param: 'exception')
end
别名：assert_raise

源代码：显示 | 在 GitHub 上查看 

# File activesupport/lib/active_support/testing/assertions.rb, line 34
def assert_raises(*exp, match: nil, &block)
  error = super(*exp, &block)
  assert_match(match, error.message) if match
  error
end