Add integration tests to ensure proper config

test/fixtures/rubocop.integration.yml

@@ -0,0 +1,8 @@
+inherit_from:
+  - ../../rubocop.yml
+
+AllCops:
+  SuggestExtensions: false # Reduce noise in test output
+
+Style/FrozenStringLiteralComment:
+  Enabled: false # We know this cop works, and having it enabled adds noise to test snippets

test/integration_test.rb

@@ -0,0 +1,210 @@
+# frozen_string_literal: true
+
+require "test_helper"
+require "tempfile"
+
+# These ensure we have rules configured to behave as expected, especially for tricky cases such as indentation.
+class IntegrationTest < Minitest::Test
+  def test_indentation
+    assert_autocorrects(<<~'DIFF')
+       sig { params(a: Something, b: SomethingElse).void }
+       def some_method(a, b)
+         unless b.something
+           b.something_else
+      -    Constant.call(ANOTHER_CONSTANT,
+      -      (T.must(b.another_thing) - b.some_time.to_i) * 1000.0)
+      +    Constant.call(
+      +      ANOTHER_CONSTANT,
+      +      (T.must(b.another_thing) - b.some_time.to_i) * 1000.0,
+      +    )
+         end
+       end
+    DIFF
+  end
+
+  def test_indentation2
+    assert_autocorrects(<<~'DIFF')
+       class ExampleController < ApplicationController
+         sig { void }
+         def create
+           @object = something
+           @object.action
+
+      -    redirect_to(a_path(@object.to_route_params),
+      -      notice: "success")
+      +    redirect_to(
+      +      a_path(@object.to_route_params),
+      +      notice: "success",
+      +    )
+         rescue SomeError
+      -    redirect_to(a_path(@object.to_route_params),
+      -      alert: "failure")
+      +    redirect_to(
+      +      a_path(@object.to_route_params),
+      +      alert: "failure",
+      +    )
+         end
+       end
+    DIFF
+  end
+
+  def test_indentation3
+    assert_autocorrects(<<~'DIFF')
+       def collection
+         Service.not_deleted.includes(
+      -    { vault_teams:
+      -        [:github_team_vault_teams, :teams] },
+      -    { app:
+      -        [{ runtimes:
+      -             [:runtime_instances, :app] },
+      -         :runtimes,
+      -         :repo,] },
+      +    {
+      +      vault_teams:
+      +        [:github_team_vault_teams, :teams],
+      +    },
+      +    {
+      +      app:
+      +        [
+      +          {
+      +            runtimes:
+      +              [:runtime_instances, :app],
+      +          },
+      +          :runtimes,
+      +          :repo,
+      +        ]
+      +    },
+           :repo,
+           :app,
+           :monorepo_mobile_app,
+           :bugsnag_project,
+           :slack_channels,
+           :vault_teams,
+           :vault_users,
+         ).joins(:app)
+       end
+    DIFF
+  end
+
+  def test_indentation4
+    skip
+    assert_autocorrects(<<~'DIFF')
+       def collection
+         Service.not_deleted.includes(
+           { vault_teams: [:github_team_vault_teams, :teams] },
+      -    { app:[
+      -      { runtimes: [:runtime_instances, :app] },
+      -         :runtimes,
+      -         :repo,] },
+      +    {
+      +      app: [
+      +        { runtimes: [:runtime_instances, :app] },
+      +        :runtimes,
+      +        :repo,
+      +      ],
+      +    },
+           :repo,
+           :app,
+           :monorepo_mobile_app,
+           :bugsnag_project,
+           :slack_channels,
+           :vault_teams,
+           :vault_users,
+         ).joins(:app)
+       end
+    DIFF
+  end
+
+  def test_indentation5
+    assert_autocorrects(<<~'DIFF')
+       # rubocop:disable Layout/LineLength
+       def pending_merge_response
+      -  { data:
+      -    { repository:
+      -      { issueOrPullRequest:
+      -        { commits:
+      -          { nodes:
+      -            [{ commit:
+      -              { statusCheckRollup:
+      -                {
+      -                  state: "PENDING",
+      -                  contexts:
+      -                  { nodes:
+      -                    [{ name: "Shopify/merge-queue",
+      -                       status: "QUEUED", }] },
+      -                } } }] } } } } }
+      +  {
+      +    data:
+      +      {
+      +        repository:
+      +          {
+      +            issueOrPullRequest:
+      +              {
+      +                commits:
+      +                  {
+      +                    nodes:
+      +                      [{
+      +                        commit:
+      +                          {
+      +                            statusCheckRollup:
+      +                              {
+      +                                state: "PENDING",
+      +                                contexts:
+      +                                  {
+      +                                    nodes:
+      +                                      [{
+      +                                        name: "Shopify/merge-queue",
+      +                                        status: "QUEUED",
+      +                                      }],
+      +                                  },
+      +                              },
+      +                          },
+      +                      }],
+      +                  },
+      +              },
+      +          },
+      +      },
+      +  }
+       end
+       # rubocop:enable Layout/LineLength
+    DIFF
+  end
+
+  private
+
+  def assert_autocorrects(diff)
+    initial, expected = split_diff(diff)
+    normalized_path = "file.rb"
+    Tempfile.create(normalized_path) do |file|
+      File.write(file.path, initial)
+      output, status = run_rubocop_on(file.path, normalized_path:)
+      actual = File.read(file.path)
+
+      assert(status.success?, "Rubocop test did not exit cleanly!\n#{indent(output)}")
+      assert_equal(expected, actual, "Autocorrection did not produce the expected output!")
+    end
+  end
+
+  def run_rubocop_on(path, normalized_path: path)
+    output, status = Open3.capture2e(
+      "bundle", "exec", "rubocop",
+      "-A",
+      "--config", File.join(__dir__, "fixtures/rubocop.integration.yml"),
+      path,
+    )
+    output.gsub!(path, normalized_path) unless path == normalized_path
+    [output, status]
+  end
+
+  # Splits a naive full file diff into the contents before and the contents after,
+  # dropping the diff prefixes (" ", "+", or "-").
+  def split_diff(diff)
+    before = diff.each_line.reject { |line| line.start_with?("+") }.map { |line| line.sub(/^[ -]/,  '') }.join
+    after  = diff.each_line.reject { |line| line.start_with?("-") }.map { |line| line.sub(/^[ \+]/, '') }.join
+    [before, after]
+  end
+
+  def indent(string, by: " " * 4 )
+    string.gsub(/^/, by)
+  end
+end