power_assert

About

Power Assert for Ruby.

Power Assert shows each value of variables and method calls in the expression. It is useful for testing, providing which value wasn’t correct when the condition is not satisfied.

Failure:
   assert { 3.times.to_a.include?(3) }
              |     |    |
              |     |    false
              |     [0, 1, 2]
              #<Enumerator: 3:times>

Related Projects

In general, you don’t need to use this library directly. Use following test frameworks or extensions instead.

• test-unit(>= 3.0.0)

  • Document

• minitest-power_assert

• rspec-power_assert

• pry-power_assert

• pry-byebug-power_assert

• power_p

Requirement

• CRuby 2.0.0 or later

Reference

• Power Assert in Ruby (at RubyKaigi 2014) // Speaker Deck

Known Limitations

• Expressions must be put in one line. Expressions with folded long lines produce nothing report, e.g.:

  assert do
    # reported
    func(foo: 0123456789, bar: "abcdefg")
  end
  
  assert do
    # won't be reported
    func(foo: 0123456789,
         bar: "abcdefg")
  end

• Expressions must have one or more method call. Expressions with no method call produce nothing report, e.g.:

  val = false
  assert do
    # reported
    val == true
  end
  
  assert do
    # won't be reported
    val
  end

• Returned values from accessor methods, method missing, or “super” produce nothing report, e.g:

  class Foo
    attr_accessor :val
  end
  foo = Foo.new
  foo.val = false
  
  assert do
    # reported (only the value of "foo" and the literal "true")
    foo.val == true
  end
  
  assert do
    # won't be reported
    foo.val
  end

• Expressions should not have conditional branches. Expressions with such conditional codes may produce nothing report, e.g.:

  condition = true
  expected = false
  actual = true
  assert do
    # this will fail but nothing reported
    condition ? expected == actual : expected == actual
  end

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