1 files changed, 57 insertions, 0 deletions
diff --git a/spec/lib/api/entities/merge_request_changes_spec.rb b/spec/lib/api/entities/merge_request_changes_spec.rb
new file mode 100644
index 00000000000..f46d8981328
--- /dev/null
+++ b/spec/lib/api/entities/merge_request_changes_spec.rb
@@ -0,0 +1,57 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe ::API::Entities::MergeRequestChanges do
+  let_it_be(:user) { create(:user) }
+  let_it_be(:merge_request) { create(:merge_request) }
+  let(:entity) { described_class.new(merge_request, current_user: user) }
+
+  subject(:basic_entity) { entity.as_json }
+
+  it "exposes basic entity fields" do
+    is_expected.to include(:changes, :overflow)
+  end
+
+  context "when #expose_raw_diffs? returns false" do
+    before do
+      expect(entity).to receive(:expose_raw_diffs?).twice.and_return(false)
+      expect_any_instance_of(Gitlab::Git::DiffCollection).to receive(:overflow?)
+    end
+
+    it "does not access merge_request.raw_diffs" do
+      expect(merge_request).not_to receive(:raw_diffs)
+
+      basic_entity
+    end
+  end
+
+  context "when #expose_raw_diffs? returns true" do
+    before do
+      expect(entity).to receive(:expose_raw_diffs?).twice.and_return(true)
+      expect_any_instance_of(Gitlab::Git::DiffCollection).not_to receive(:overflow?)
+    end
+
+    it "does not access merge_request.raw_diffs" do
+      expect(merge_request).to receive(:raw_diffs)
+
+      basic_entity
+    end
+  end
+
+  describe ":overflow field" do
+    context "when :access_raw_diffs is true" do
+      let_it_be(:entity_with_raw_diffs) do
+        described_class.new(merge_request, current_user: user, access_raw_diffs: true).as_json
+      end
+
+      before do
+        expect_any_instance_of(Gitlab::Git::DiffCollection).not_to receive(:overflow?)
+      end
+
+      it "reports false" do
+        expect(entity_with_raw_diffs[:overflow]).to be_falsy
+      end
+    end
+  end
+end