Ruby - Set key-value pairs inside array of hashes

Question

The problem is: I have a method

def comparison_reporter(list_of_scenarios_results1, list_of_scenarios_results2)
  actual_failed_tests = list_of_scenarios_results2.select {|k,v| v == 'Failed'}
  actual_passed_tests = list_of_scenarios_results2.select {|k,v| v == 'Passed'}
  failed_tests = Array.new(actual_failed_tests.length) { Hash.new }
  failed_tests.each do |hash|
      actual_failed_tests.keys.map {|name| hash["test_name"] = name}
      actual_failed_tests.values.map {|new_status| hash["actual_status"] = new_status}
      list_of_scenarios_results1.values_at(*actual_failed_tests.keys).map {|old_status| hash["previous_status"] = old_status}
  end
  final_result = {
    "passed_tests_count" => list_of_scenarios_results2.select {|k,v| v == 'Passed'}.length,
    "failed_tests_count" => list_of_scenarios_results2.select {|k,v| v == 'Failed'}.length,
    "failed_tests" => failed_tests
  }
  return final_result
end

This method takes 2 hashes as arguments and returns the result of their comparison and some other things. Currently, it always returns failed_tests with two (or more) identical hashes (same key-value pairs). I think, that problem is somewhere in failed_tests.each do |hash| block, but I can't find the reason of this bug, please advice. Example of the method result (in .json format)

{
  "passed_tests_count": 3,
  "failed_tests_count": 2,
  "failed_tests": [
    {
      "test_name": "As a user I want to use Recent searches tab",
      "actual_status": "Failed",
      "previous_status": "Failed"
    },
    {
      "test_name": "As a user I want to use Recent searches tab",
      "actual_status": "Failed",
      "previous_status": "Failed"
    }
  ]
}

UPD: hash1 (first argument) -

{""=>"Passed",
"As a new user I want to use no fee rentals tab"=>"Passed",
"As a new user I want to use Luxury rentals tab"=>"Passed", 
"As a user I want to use Recent searches tab"=>"Failed",
"As a user I want to use new listings for you tab"=>"Passed"}

hash2 (second argument)-

{""=>"Passed",
"As a new user I want to use no fee rentals tab"=>"Failed",
"As a new user I want to use Luxury rentals tab"=>"Passed",
"As a user I want to use Recent searches tab"=>"Failed",
"As a user I want to use new listings for you tab"=>"Passed"}

Example of desired desired output:

{ 
"passed":"count",
"failed":"count",
"failed_tests": [
   {"test_name":"As a user I want to use Recent searches tab",
    "actual_status":"failed",
    "previous_status":"failed"},
   {"test_name":"As a new user I want to use no fee rentals tab",
    "actual_status":"failed",
    "previous_status":"passed"}]
}

Answer 1

Solution:

def comparison_reporter(before, after)
  failed_tests = after.select { |k,v| v == "Failed" }.map do |k,v|
    {
      test_name: k,
      actual_status: v,
      previous_status: before[k]
    }
  end

  {
    passed: after.size - failed_tests.size,
    failed: failed_tests.size,
    failed_tests: failed_tests
  }
end

Simplified failed_tests quite a bit. Since we calculate number of failed tests, we can use it for the final counts, instead of iterating over the hash again.

Answer 2

The problem is on line 8: You're overwriting hash["previous_status"] with the last value in list_of_scenarios_results1.values_at(*actual_failed_tests.keys) when you map over it.

Usually you use map to assign an iterable to something, not modify something else. eg
x = ['1','2','3'].map(&:to_i)
rather than
x = []; ['1','2','3'].map {|v| x << v.to_i}

I'd suggest re-thinking your approach. Will you always have the same keys in both hashes? If so you could simplify this. I'd also suggest looking into byebug . It's an interactive debugger that'll let you step through your function and see where things aren't doing what you expect.