Add comprehensive test suite with unit and integration tests

testdata/test.pdf

@@ -0,0 +1,58 @@
+%PDF-1.4
+1 0 obj
+<<
+/Type /Catalog
+/Pages 2 0 R
+>>
+endobj
+2 0 obj
+<<
+/Type /Pages
+/Kids [3 0 R]
+/Count 1
+>>
+endobj
+3 0 obj
+<<
+/Type /Page
+/Parent 2 0 R
+/Resources <<
+/Font <<
+/F1 <<
+/Type /Font
+/Subtype /Type1
+/BaseFont /Helvetica
+>>
+>>
+>>
+/MediaBox [0 0 612 792]
+/Contents 4 0 R
+>>
+endobj
+4 0 obj
+<<
+/Length 44
+>>
+stream
+BT
+/F1 12 Tf
+100 700 Td
+(Test PDF) Tj
+ET
+endstream
+endobj
+xref
+0 5
+0000000000 65535 f
+0000000009 00000 n
+0000000058 00000 n
+0000000115 00000 n
+0000000317 00000 n
+trailer
+<<
+/Size 5
+/Root 1 0 R
+>>
+startxref
+408
+%%EOF

testdata/test.txt

@@ -0,0 +1 @@
+This is a test text file for attachment testing.