result_test.rb

# typed: true

require "minitest/autorun"
require_relative "../lib/result"

class TestResult < Minitest::Test
  def test_unwrap_success_returns_value
    r = Result.ok("val")
    assert_equal r.unwrap, "val"
  end

  def test_unwrap_error_raises
    r = Result.err("oh no")
    err = assert_raises(Result::UnwrapError) {
      r.unwrap
    }

    assert_equal err.message, "called `Result::unwrap` on a Failure containing: 'oh no'"
  end

  def test_map_success_maps_value
    r = Result.ok(2).map { |v| v * 2 }

    assert_equal r.unwrap, 4
  end

  def test_map_failure_does_not_map_and_retains_error
    r = Result.err("oh no").map { |v| raise "unexpected mapping" }

    err = assert_raises(Result::UnwrapError) {
      r.unwrap
    }

    assert_equal err.message, "called `Result::unwrap` on a Failure containing: 'oh no'"
  end

  def test_and_then_success
    r = Result.ok("str-to-len").and_then { |v| Result.ok(v.length) }

    assert_equal r.unwrap, 10
  end

  def test_and_then_failure
    r = Result.err("oh no").and_then { |v| raise "unexpected and_thenning" }

    err = assert_raises(Result::UnwrapError) {
      r.unwrap
    }

    assert_equal err.message, "called `Result::unwrap` on a Failure containing: 'oh no'"
  end

  def test_map_err_success_does_not_map_and_retains_error
    r = Result.ok(2).map_err { |v| raise "unexpected mapping" }
    assert_equal r.unwrap, 2
  end

  def test_map_err_failure_maps_err
    r = Result.err(2).map_err { |v| v * 2 }
    assert_equal r.unwrap, 2
  end
end