diff --git a/app/utils/markdown-export.test.ts b/app/utils/markdown-export.test.ts
index 9868085..60ef3e6 100644
--- a/app/utils/markdown-export.test.ts
+++ b/app/utils/markdown-export.test.ts
@@ -1,6 +1,7 @@
 import { describe, expect, test } from "bun:test";
 import {
   buildMarkdownExportFileName,
+  downloadMarkdownFile,
   normalizeMarkdownImageUrls,
 } from "./markdown-export";
 
@@ -55,3 +56,126 @@ describe("buildMarkdownExportFileName", () => {
     expect(result).toBe("post-42.md");
   });
 });
+
+describe("downloadMarkdownFile", () => {
+  test("does not throw when window/document are unavailable", () => {
+    const windowDescriptor = Object.getOwnPropertyDescriptor(globalThis, "window");
+    const documentDescriptor = Object.getOwnPropertyDescriptor(globalThis, "document");
+
+    Object.defineProperty(globalThis, "window", {
+      value: undefined,
+      configurable: true,
+      writable: true,
+    });
+    Object.defineProperty(globalThis, "document", {
+      value: undefined,
+      configurable: true,
+      writable: true,
+    });
+
+    try {
+      expect(() => downloadMarkdownFile("post.md", "# hello")).not.toThrow();
+    } finally {
+      if (windowDescriptor) {
+        Object.defineProperty(globalThis, "window", windowDescriptor);
+      } else {
+        Reflect.deleteProperty(globalThis, "window");
+      }
+
+      if (documentDescriptor) {
+        Object.defineProperty(globalThis, "document", documentDescriptor);
+      } else {
+        Reflect.deleteProperty(globalThis, "document");
+      }
+    }
+  });
+
+  test("creates object URL, clicks anchor, and revokes URL in browser flow", () => {
+    const windowDescriptor = Object.getOwnPropertyDescriptor(globalThis, "window");
+    const documentDescriptor = Object.getOwnPropertyDescriptor(globalThis, "document");
+    const urlDescriptor = Object.getOwnPropertyDescriptor(globalThis, "URL");
+
+    let createElementArg = "";
+    let appendedNode: unknown;
+    let clicked = false;
+    let removed = false;
+    let revokedArg = "";
+    const blobUrl = "blob:test-url";
+
+    const anchor = {
+      href: "",
+      download: "",
+      style: { display: "" },
+      click: () => {
+        clicked = true;
+      },
+      remove: () => {
+        removed = true;
+      },
+    };
+
+    Object.defineProperty(globalThis, "window", {
+      value: {},
+      configurable: true,
+      writable: true,
+    });
+
+    Object.defineProperty(globalThis, "document", {
+      value: {
+        createElement: (tag: string) => {
+          createElementArg = tag;
+          return anchor;
+        },
+        body: {
+          appendChild: (node: unknown) => {
+            appendedNode = node;
+          },
+        },
+      },
+      configurable: true,
+      writable: true,
+    });
+
+    Object.defineProperty(globalThis, "URL", {
+      value: {
+        createObjectURL: (_blob: Blob) => blobUrl,
+        revokeObjectURL: (url: string) => {
+          revokedArg = url;
+        },
+      },
+      configurable: true,
+      writable: true,
+    });
+
+    try {
+      downloadMarkdownFile("hello.md", "# hello");
+
+      expect(createElementArg).toBe("a");
+      expect(appendedNode).toBe(anchor);
+      expect(anchor.href).toBe(blobUrl);
+      expect(anchor.download).toBe("hello.md");
+      expect(anchor.style.display).toBe("none");
+      expect(clicked).toBe(true);
+      expect(removed).toBe(true);
+      expect(revokedArg).toBe(blobUrl);
+    } finally {
+      if (windowDescriptor) {
+        Object.defineProperty(globalThis, "window", windowDescriptor);
+      } else {
+        Reflect.deleteProperty(globalThis, "window");
+      }
+
+      if (documentDescriptor) {
+        Object.defineProperty(globalThis, "document", documentDescriptor);
+      } else {
+        Reflect.deleteProperty(globalThis, "document");
+      }
+
+      if (urlDescriptor) {
+        Object.defineProperty(globalThis, "URL", urlDescriptor);
+      } else {
+        Reflect.deleteProperty(globalThis, "URL");
+      }
+    }
+  });
+});