広場投稿追加画面の刷新 (#399) (#413)

Reviewed-on: #413
Co-authored-by: miteruzo <miteruzo@naver.com>
Co-committed-by: miteruzo <miteruzo@naver.com>

backend/spec/services/post_thumbnail_upload_validator_spec.rb

@@ -0,0 +1,52 @@
+require 'rails_helper'
+require 'base64'
+require 'tempfile'
+
+RSpec.describe PostThumbnailUploadValidator do
+  def with_upload bytes, content_type:, filename:
+    tempfile = Tempfile.new(['thumbnail-upload', File.extname(filename)])
+    tempfile.binmode
+    tempfile.write(bytes)
+    tempfile.rewind
+    upload = ActionDispatch::Http::UploadedFile.new(
+        tempfile:,
+        filename:,
+        type: content_type)
+    yield upload
+  ensure
+    tempfile&.close!
+  end
+
+  it 'accepts a raster upload after decoding and rewinds it' do
+    gif = Base64.decode64('R0lGODdhAQABAIABAP///wAAACwAAAAAAQABAAACAkQBADs=')
+
+    with_upload(gif, content_type: 'image/gif', filename: 'thumbnail.gif') do |upload|
+      expect { described_class.validate!(upload) }.not_to raise_error
+      expect(upload.read(6)).to eq('GIF87a')
+    end
+  end
+
+  it 'rejects SVG content disguised as a raster MIME type' do
+    with_upload(
+        '<svg width="10" height="10"></svg>',
+        content_type: 'image/png',
+        filename: 'thumbnail.png') do |upload|
+      expect { described_class.validate!(upload) }
+          .to raise_error(
+              described_class::InvalidUpload,
+              'サムネイル画像の形式が不正です．')
+    end
+  end
+
+  it 'rejects non-raster content disguised as an image' do
+    with_upload(
+        '%PDF-1.7',
+        content_type: 'image/png',
+        filename: 'thumbnail.png') do |upload|
+      expect { described_class.validate!(upload) }
+          .to raise_error(
+              described_class::InvalidUpload,
+              'サムネイル画像の形式が不正です．')
+    end
+  end
+end