Checking an edge case for git strategy

lib/churn_vs_complexity/git_strategy.rb

@@ -15,7 +15,9 @@ def valid_commit?(commit:)
     end
 
     def changes(commit:)
-      @repo.object(commit).diff(@repo.object(commit).parent).map do |change|
+      commit_object = @repo.object(commit)
+      base = commit_object.parent
+      commit_object.diff(base).map do |change|
         { path: change.path, type: change.type.to_sym }
       end
     end

test/churn_vs_complexity/delta/checker_test.rb

@@ -11,7 +11,7 @@ class CheckerTest < TLDR
       # Idea for check algorithm:
       # 1. Find commit in log
       # 2. Find all files changed in this commit
-      #  3. Annotate changed files with type of change (create, delete, modify)
+      # 3. Annotate changed files with type of change (create, delete, modify)
       # 4. Validate changed files with complexity validator
       # 5. Serialize results
 
@@ -37,10 +37,10 @@ def test_that_it_fails_when_it_cannot_prepare_a_worktree_and_there_are_changes
         end
       end
 
-      def test_that_it_fails_when_it_cannot_check_out_a_worktree_for_commit_and_there_are_changes
-        f = factory(worktree: worktree(fail_to_checkout: true))
-        # TODO: move worktree up one level
-        assert_raises(Timetravel::Worktree::Error) do
+      def test_that_it_fails_when_it_cannot_calculate_complexity_for_a_file
+        f = factory()
+        # TODO: wire Engine for custom complexity calculator        
+        assert_raises(StandardError) do
           checker(factory: f).check(folder: 'space-place')
         end
       end

test/churn_vs_complexity/git_strategy_integration_test.rb

@@ -0,0 +1,28 @@
+# frozen_string_literal: true
+
+require 'test_helper'
+
+module ChurnVsComplexity
+  class GitStrategyIntegrationTest < TLDR
+
+    def test_that_it_can_get_changes_for_the_first_commit
+      g = GitStrategy.new(folder: ROOT_PATH)
+      repo = Git.open(ROOT_PATH)
+
+      first_commit = repo.log(max_count = 100_000).last.sha
+
+      changes = g.changes(commit: first_commit)
+      assert changes.any?, "No changes found for first commit #{first_commit}"
+    end
+
+    def test_that_it_can_get_changes_for_the_last_commit
+      g = GitStrategy.new(folder: ROOT_PATH)
+      repo = Git.open(ROOT_PATH)
+
+      last_commit = repo.log.first.sha
+
+      changes = g.changes(commit: last_commit)
+      assert changes.any?, "No changes found for last commit #{last_commit}"
+    end
+  end
+end