feat(tests): add comprehensive tests for MarkItDown

Introduce new test cases for various file formats including XLSX, 
DOCX, PPTX, RSS, and CSV. a validation utility to 
the output strings match expected results. These changes enhance 
test coverage and ensure the reliability of the MarkItDown 
conversion functionality.

tests/core/test_local_file.py

@@ -0,0 +1,155 @@
+import os
+from pathlib import Path
+
+import pytest
+
+from markitdown import MarkItDown
+from tests.helpers.utils import validate_strings
+
+TEST_FILES_DIR = Path(__file__).parent.parent / "test_files"
+
+XLSX_TEST_STRINGS = [
+    "## 09060124-b5e7-4717-9d07-3c046eb",
+    "6ff4173b-42a5-4784-9b19-f49caff4d93d",
+    "affc7dad-52dc-4b98-9b5d-51e65d8a8ad0",
+]
+
+DOCX_TEST_STRINGS = [
+    "314b0a30-5b04-470b-b9f7-eed2c2bec74a",
+    "49e168b7-d2ae-407f-a055-2167576f39a1",
+    "## d666f1f7-46cb-42bd-9a39-9a39cf2a509f",
+    "# Abstract",
+    "# Introduction",
+    "AutoGen: Enabling Next-Gen LLM Applications via Multi-Agent Conversation",
+]
+
+DOCX_COMMENT_TEST_STRINGS = [
+    "314b0a30-5b04-470b-b9f7-eed2c2bec74a",
+    "49e168b7-d2ae-407f-a055-2167576f39a1",
+    "## d666f1f7-46cb-42bd-9a39-9a39cf2a509f",
+    "# Abstract",
+    "# Introduction",
+    "AutoGen: Enabling Next-Gen LLM Applications via Multi-Agent Conversation",
+    "This is a test comment. 12df-321a",
+    "Yet another comment in the doc. 55yiyi-asd09",
+]
+
+PPTX_TEST_STRINGS = [
+    "2cdda5c8-e50e-4db4-b5f0-9722a649f455",
+    "04191ea8-5c73-4215-a1d3-1cfb43aaaf12",
+    "44bf7d06-5e7a-4a40-a2e1-a2e42ef28c8a",
+    "1b92870d-e3b5-4e65-8153-919f4ff45592",
+    "AutoGen: Enabling Next-Gen LLM Applications via Multi-Agent Conversation",
+    "a3f6004b-6f4f-4ea8-bee3-3741f4dc385f",  # chart title
+    "2003",  # chart value
+]
+
+BLOG_TEST_URL = "https://microsoft.github.io/autogen/blog/2023/04/21/LLM-tuning-math"
+BLOG_TEST_STRINGS = [
+    "Large language models (LLMs) are powerful tools that can generate natural language texts for various applications, such as chatbots, summarization, translation, and more. GPT-4 is currently the state of the art LLM in the world. Is model selection irrelevant? What about inference parameters?",
+    "an example where high cost can easily prevent a generic complex",
+]
+
+
+RSS_TEST_STRINGS = [
+    "The Official Microsoft Blog",
+    "In the case of AI, it is absolutely true that the industry is moving incredibly fast",
+]
+
+
+WIKIPEDIA_TEST_URL = "https://en.wikipedia.org/wiki/Microsoft"
+WIKIPEDIA_TEST_STRINGS = [
+    "Microsoft entered the operating system (OS) business in 1980 with its own version of [Unix]",
+    'Microsoft was founded by [Bill Gates](/wiki/Bill_Gates "Bill Gates")',
+]
+WIKIPEDIA_TEST_EXCLUDES = [
+    "You are encouraged to create an account and log in",
+    "154 languages",
+    "move to sidebar",
+]
+
+SERP_TEST_URL = "https://www.bing.com/search?q=microsoft+wikipedia"
+SERP_TEST_STRINGS = [
+    "](https://en.wikipedia.org/wiki/Microsoft",
+    "Microsoft Corporation is **an American multinational corporation and technology company headquartered** in Redmond",
+    "1995–2007: Foray into the Web, Windows 95, Windows XP, and Xbox",
+]
+SERP_TEST_EXCLUDES = [
+    "https://www.bing.com/ck/a?!&&p=",
+    "data:image/svg+xml,%3Csvg%20width%3D",
+]
+
+CSV_CP932_TEST_STRINGS = [
+    "名前,年齢,住所",
+    "佐藤太郎,30,東京",
+    "三木英子,25,大阪",
+    "髙橋淳,35,名古屋",
+]
+
+
+@pytest.fixture
+def markitdown() -> MarkItDown:
+    return MarkItDown()
+
+
+@pytest.mark.parametrize(
+    "filename, expected_strings, exclude_strings, kwargs",
+    [
+        ("test.xlsx", XLSX_TEST_STRINGS, None, {}),
+        ("test.docx", DOCX_TEST_STRINGS, None, {}),
+        (
+            "test_with_comment.docx",
+            DOCX_COMMENT_TEST_STRINGS,
+            None,
+            {"style_map": "comment-reference => "},
+        ),
+        ("test.pptx", PPTX_TEST_STRINGS, None, {}),
+        ("test_blog.html", BLOG_TEST_STRINGS, None, {"url": BLOG_TEST_URL}),
+        ("test_files.zip", XLSX_TEST_STRINGS, None, {}),
+        (
+            "test_wikipedia.html",
+            WIKIPEDIA_TEST_STRINGS,
+            WIKIPEDIA_TEST_EXCLUDES,
+            {"url": WIKIPEDIA_TEST_URL},
+        ),
+        (
+            "test_serp.html",
+            SERP_TEST_STRINGS,
+            SERP_TEST_EXCLUDES,
+            {"url": SERP_TEST_URL},
+        ),
+        ("test_rss.xml", RSS_TEST_STRINGS, None, {}),
+        ("test_mskanji.csv", CSV_CP932_TEST_STRINGS, None, {}),
+    ],
+)
+def test_common(
+    markitdown: MarkItDown,
+    filename: str,
+    expected_strings: list,
+    exclude_strings: list,
+    kwargs,
+) -> None:
+    source = TEST_FILES_DIR / filename
+    result = markitdown.convert(source, **kwargs)
+    validate_strings(result, expected_strings, exclude_strings)
+
+
+def test_docx() -> None:
+    markitdown = MarkItDown()
+    # Test DOCX processing
+    result = markitdown.convert(os.path.join(TEST_FILES_DIR, "test.docx"))
+    validate_strings(result, DOCX_TEST_STRINGS)
+
+    # Test DOCX processing, with comments
+    result = markitdown.convert(
+        os.path.join(TEST_FILES_DIR, "test_with_comment.docx"),
+        style_map="comment-reference => ",
+    )
+    validate_strings(result, DOCX_COMMENT_TEST_STRINGS)
+
+    # Test DOCX processing, with comments and setting style_map on init
+    markitdown_with_style_map = MarkItDown(style_map="comment-reference => ")
+    result = markitdown_with_style_map.convert(
+        os.path.join(TEST_FILES_DIR, "test_with_comment.docx")
+    )
+    validate_strings(result, DOCX_COMMENT_TEST_STRINGS)

tests/helpers/utils.py

@@ -0,0 +1,11 @@
+# --- Helper Functions ---
+
+
+def validate_strings(result, expected_strings, exclude_strings=None):
+    """Validate presence or absence of specific strings."""
+    text_content = result.text_content.replace("\\", "")
+    for string in expected_strings:
+        assert string in text_content
+    if exclude_strings:
+        for string in exclude_strings:
+            assert string not in text_content