Minitest assert_equal sucks for comparing output diffs of two hashes. Using HashDiff, awesome_print, and StringIO we can get actual comparable hashes without pulling our hair out.

nice_hash_comparison_test.rb

require "test_helper"
require "awesome_print"
require "hashdiff"

class MyClass
  def self.do_stuff
    {a:[{y:3}, {x:11, z:33}], b:{y:22}}
  end
end

class MyClassTest < ::Minitest::Test

  def test_stuff
    expected = {a:[{x:2, y:3, z:4}, {x:11, y:22, z:33}], b:{x:3, z:45}}

    actual = MyClass.do_stuff

    diff = ::HashDiff.diff(expected, actual)
    if diff.empty?
      pass("Hashes are equal")
    else
      out = StringIO.new
      grouped = diff.group_by(&:first)
      if grouped["~"]
        out.puts "\nDifferent Values (left, right):"
        grouped["~"].each do |(_, field, left, right)|
          out.puts "\t#{field}: '#{left.inspect}', '#{right.inspect}'"
        end
      end

      if grouped["-"]
        out.puts "\nMissing Values from right (left):"
        grouped["-"].each do |(_, field, left)|
          out.puts "\t#{field}: '#{left.inspect}'"
        end
      end

      if grouped["+"]
        out.puts "\nMissing Values from left (right):"
        grouped["+"].each do |(_, field, right)|
          out.puts "\t#{field}: '#{right.inspect}'"
        end
      end

      ap_opts = { indent: 2 }
      out.puts
      out.puts "Expected"
      out.puts "--------"
      out.puts expected.ai(ap_opts)

      out.puts
      out.puts "Actual"
      out.puts "------"
      out.puts actual.ai(ap_opts)

      out.rewind
      flunk("Hashes are not equal:\n\n#{out.read}")
    end
  end
end

out.txt

MyClassTest#test_stuff [/path/to/nice_hash_comparison_test.rb:56]:
Hashes are not equal:


Missing Values from right (left):
	a[1].y: '22'
	a[0]: '{:x=>2, :y=>3, :z=>4}'
	b.x: '3'
	b.z: '45'

Missing Values from left (right):
	a[0]: '{:y=>3}'
	b.y: '22'

Expected
--------
{
  :a => [
    [0] {
      :x => 2,
      :y => 3,
      :z => 4
    },
    [1] {
      :x => 11,
      :y => 22,
      :z => 33
    }
  ],
  :b => {
    :x => 3,
    :z => 45
  }
}

Actual
------
{
  :a => [
    [0] {
      :y => 3
    },
    [1] {
      :x => 11,
      :z => 33
    }
  ],
  :b => {
    :y => 22
  }
}

[make_my_diffs_pretty!](https://www.rubydoc.info/github/seattlerb/minitest/Minitest%2FTest.make_my_diffs_pretty!) in test/test_helper.rb (if on Rails) does a pretty good job, though, too.

HashDiff should be Hashdiff

@fwolfst Thanks for this pointer! Didn't know about the pretty diff feature! ❤️

Just came across this and it's awesome. Would you be able to declare an MIT license for it, or else declare it as public domain?

@mvastola definitely free and available for public domain.