Add MCP server code

tests/test_get_page_image.py

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+import os
+from pathlib import Path
+
+from mcp.server.fastmcp import Image
+
+from pdf_mcp.server import get_page_image
+
+
+class TestGetPageImageBase64:
+    def test_returns_image_object(self, basic_pdf):
+        result = get_page_image(basic_pdf, page=1)
+        assert isinstance(result, Image)
+
+    def test_image_has_data(self, basic_pdf):
+        result = get_page_image(basic_pdf, page=1)
+        assert len(result.data) > 0
+
+    def test_png_signature(self, basic_pdf):
+        result = get_page_image(basic_pdf, page=1)
+        # PNG files start with the 8-byte signature
+        assert result.data[:4] == b"\x89PNG"
+
+    def test_different_pages(self, basic_pdf):
+        img1 = get_page_image(basic_pdf, page=1)
+        img2 = get_page_image(basic_pdf, page=2)
+        assert img1.data != img2.data
+
+
+class TestGetPageImageFile:
+    def test_returns_string_with_path(self, basic_pdf):
+        result = get_page_image(basic_pdf, page=1, output="file")
+        assert isinstance(result, str)
+        assert "Image saved to" in result
+
+    def test_file_exists(self, basic_pdf):
+        result = get_page_image(basic_pdf, page=1, output="file")
+        # Extract path from "Image saved to /path/to/file.png (WxHpx)"
+        path = result.split("Image saved to ")[1].split(" (")[0]
+        assert Path(path).exists()
+        os.unlink(path)
+
+    def test_file_is_valid_png(self, basic_pdf):
+        result = get_page_image(basic_pdf, page=1, output="file")
+        path = result.split("Image saved to ")[1].split(" (")[0]
+        with open(path, "rb") as f:
+            assert f.read(4) == b"\x89PNG"
+        os.unlink(path)
+
+    def test_file_includes_dimensions(self, basic_pdf):
+        result = get_page_image(basic_pdf, page=1, output="file")
+        # Should contain something like "(1240x1754px)"
+        assert "px)" in result
+
+
+class TestGetPageImageDpi:
+    def test_higher_dpi_larger_file(self, basic_pdf):
+        low = get_page_image(basic_pdf, page=1, dpi=72)
+        high = get_page_image(basic_pdf, page=1, dpi=300)
+        assert len(high.data) > len(low.data)
+
+    def test_default_dpi(self, basic_pdf):
+        default = get_page_image(basic_pdf, page=1)
+        explicit_150 = get_page_image(basic_pdf, page=1, dpi=150)
+        assert len(default.data) == len(explicit_150.data)
+
+
+class TestGetPageImageDiagrams:
+    def test_diagrams_renders(self, diagrams_pdf):
+        result = get_page_image(diagrams_pdf, page=1)
+        assert isinstance(result, Image)
+        assert len(result.data) > 0
+
+    def test_diagrams_file_output(self, diagrams_pdf):
+        result = get_page_image(diagrams_pdf, page=1, output="file")
+        path = result.split("Image saved to ")[1].split(" (")[0]
+        assert Path(path).exists()
+        assert Path(path).stat().st_size > 0
+        os.unlink(path)