diff --git a/src/index.js b/src/index.js
index aeac172..15c9d7d 100644
--- a/src/index.js
+++ b/src/index.js
@@ -13,6 +13,7 @@ try {
 }
 
 process.dirname = __dirname;
+process.filename = __filename;
 
 // TODO: after implementing clustering in new SVR.JS
 //process.singleThreaded = false;
diff --git a/src/middleware/checkForbiddenPaths.js b/src/middleware/checkForbiddenPaths.js
index 97d07ee..0923a86 100644
--- a/src/middleware/checkForbiddenPaths.js
+++ b/src/middleware/checkForbiddenPaths.js
@@ -1,81 +1,11 @@
-const os = require("os");
-const path = require("path");
-
-// Function to get URL path for use in forbidden path adding.
-function getInitializePath(to) {
-  const cwd = process.cwd();
-  if (os.platform() == "win32") {
-    to = to.replace(/\//g, "\\");
-    if (to[0] == "\\") to = cwd.split("\\")[0] + to;
-  }
-  const absoluteTo = path.isAbsolute(to)
-    ? to
-    : process.dirname + (os.platform() == "win32" ? "\\" : "/") + to;
-  if (os.platform() == "win32" && cwd[0] != absoluteTo[0]) return "";
-  const relative = path.relative(cwd, absoluteTo);
-  if (os.platform() == "win32") {
-    return "/" + relative.replace(/\\/g, "/");
-  } else {
-    return "/" + relative;
-  }
-}
-
-// Function to check if URL path name is a forbidden path.
-function isForbiddenPath(decodedHref, match) {
-  const forbiddenPath = forbiddenPaths[match];
-  if (!forbiddenPath) return false;
-  if (typeof forbiddenPath === "string") {
-    return (
-      decodedHref === forbiddenPath ||
-      (os.platform() === "win32" &&
-        decodedHref.toLowerCase() === forbiddenPath.toLowerCase())
-    );
-  }
-  if (typeof forbiddenPath === "object") {
-    return forbiddenPath.some(function (forbiddenPathSingle) {
-      return (
-        decodedHref === forbiddenPathSingle ||
-        (os.platform() === "win32" &&
-          decodedHref.toLowerCase() === forbiddenPathSingle.toLowerCase())
-      );
-    });
-  }
-  return false;
-}
-
-// Function to check if URL path name is index of one of defined forbidden paths.
-function isIndexOfForbiddenPath(decodedHref, match) {
-  const forbiddenPath = forbiddenPaths[match];
-  if (!forbiddenPath) return false;
-  if (typeof forbiddenPath === "string") {
-    return (
-      decodedHref === forbiddenPath ||
-      decodedHref.indexOf(forbiddenPath + "/") === 0 ||
-      (os.platform() === "win32" &&
-        (decodedHref.toLowerCase() === forbiddenPath.toLowerCase() ||
-          decodedHref
-            .toLowerCase()
-            .indexOf(forbiddenPath.toLowerCase() + "/") === 0))
-    );
-  }
-  if (typeof forbiddenPath === "object") {
-    return forbiddenPath.some(function (forbiddenPathSingle) {
-      return (
-        decodedHref === forbiddenPathSingle ||
-        decodedHref.indexOf(forbiddenPathSingle + "/") === 0 ||
-        (os.platform() === "win32" &&
-          (decodedHref.toLowerCase() === forbiddenPathSingle.toLowerCase() ||
-            decodedHref
-              .toLowerCase()
-              .indexOf(forbiddenPathSingle.toLowerCase() + "/") === 0))
-      );
-    });
-  }
-  return false;
-}
-
-// Set up forbidden paths
-var forbiddenPaths = {};
+// WARNING: This middleware is optimized for production SVR.JS, and may not work correctly for development SVR.JS.
+// Use "npm run dev" to test SVR.JS web server itself.
+const {
+  getInitializePath,
+  isForbiddenPath,
+  isIndexOfForbiddenPath,
+  forbiddenPaths,
+} = require("../utils/forbiddenPaths.js");
 
 forbiddenPaths.config = getInitializePath("./config.json");
 forbiddenPaths.certificates = [];
@@ -96,8 +26,8 @@ if (process.serverConfig.secure) {
 forbiddenPaths.svrjs = getInitializePath(
   "./" +
     (process.dirname[process.dirname.length - 1] != "/"
-      ? __filename.replace(process.dirname + "/", "")
-      : __filename.replace(process.dirname, "")),
+      ? process.filename.replace(process.dirname + "/", "")
+      : process.filename.replace(process.dirname, "")),
 );
 forbiddenPaths.serverSideScripts = [];
 if (process.serverConfig.useWebRootServerSideScript) {
diff --git a/src/utils/forbiddenPaths.js b/src/utils/forbiddenPaths.js
new file mode 100644
index 0000000..be76508
--- /dev/null
+++ b/src/utils/forbiddenPaths.js
@@ -0,0 +1,87 @@
+const os = require("os");
+const path = require("path");
+
+// Function to get URL path for use in forbidden path adding.
+function getInitializePath(to) {
+  const isWin32 = os.platform() == "win32";
+  const pathModS = isWin32 ? path.win32 : path.posix; // pathModS needed just for the test suite
+  const cwd = process.cwd();
+  if (isWin32) {
+    to = to.replace(/\//g, "\\");
+    if (to[0] == "\\") to = cwd.split("\\")[0] + to;
+  }
+  const absoluteTo = pathModS.isAbsolute(to)
+    ? to
+    : process.dirname + (isWin32 ? "\\" : "/") + to;
+  if (isWin32 && cwd[0] != absoluteTo[0]) return "";
+  const relative = pathModS.relative(cwd, absoluteTo);
+  if (isWin32) {
+    return "/" + relative.replace(/\\/g, "/");
+  } else {
+    return "/" + relative;
+  }
+}
+
+// Function to check if URL path name is a forbidden path.
+function isForbiddenPath(decodedHref, match) {
+  const forbiddenPath = forbiddenPaths[match];
+  if (!forbiddenPath) return false;
+  if (typeof forbiddenPath === "string") {
+    return (
+      decodedHref === forbiddenPath ||
+      (os.platform() === "win32" &&
+        decodedHref.toLowerCase() === forbiddenPath.toLowerCase())
+    );
+  }
+  if (typeof forbiddenPath === "object") {
+    return forbiddenPath.some(function (forbiddenPathSingle) {
+      return (
+        decodedHref === forbiddenPathSingle ||
+        (os.platform() === "win32" &&
+          decodedHref.toLowerCase() === forbiddenPathSingle.toLowerCase())
+      );
+    });
+  }
+  return false;
+}
+
+// Function to check if URL path name is index of one of defined forbidden paths.
+function isIndexOfForbiddenPath(decodedHref, match) {
+  const forbiddenPath = forbiddenPaths[match];
+  if (!forbiddenPath) return false;
+  if (typeof forbiddenPath === "string") {
+    return (
+      decodedHref === forbiddenPath ||
+      decodedHref.indexOf(forbiddenPath + "/") === 0 ||
+      (os.platform() === "win32" &&
+        (decodedHref.toLowerCase() === forbiddenPath.toLowerCase() ||
+          decodedHref
+            .toLowerCase()
+            .indexOf(forbiddenPath.toLowerCase() + "/") === 0))
+    );
+  }
+  if (typeof forbiddenPath === "object") {
+    return forbiddenPath.some(function (forbiddenPathSingle) {
+      return (
+        decodedHref === forbiddenPathSingle ||
+        decodedHref.indexOf(forbiddenPathSingle + "/") === 0 ||
+        (os.platform() === "win32" &&
+          (decodedHref.toLowerCase() === forbiddenPathSingle.toLowerCase() ||
+            decodedHref
+              .toLowerCase()
+              .indexOf(forbiddenPathSingle.toLowerCase() + "/") === 0))
+      );
+    });
+  }
+  return false;
+}
+
+// Set up forbidden paths
+let forbiddenPaths = {};
+
+module.exports = {
+  getInitializePath: getInitializePath,
+  isForbiddenPath: isForbiddenPath,
+  isIndexOfForbiddenPath: isIndexOfForbiddenPath,
+  forbiddenPaths: forbiddenPaths,
+};
diff --git a/tests/utils/forbiddenPaths.test.js b/tests/utils/forbiddenPaths.test.js
new file mode 100644
index 0000000..1ae2775
--- /dev/null
+++ b/tests/utils/forbiddenPaths.test.js
@@ -0,0 +1,147 @@
+const {
+  getInitializePath,
+  isForbiddenPath,
+  isIndexOfForbiddenPath,
+  forbiddenPaths,
+} = require("../../src/utils/forbiddenPaths");
+const os = require("os");
+const path = require("path");
+
+jest.mock("os", () => ({
+  platform: jest.fn(),
+}));
+
+describe("Forbidden paths handling", () => {
+  beforeEach(() => {
+    os.platform.mockReset();
+    forbiddenPaths.config = getInitializePath("./config.json");
+    forbiddenPaths.serverSideScriptDirectories = [];
+    forbiddenPaths.serverSideScriptDirectories.push(
+      getInitializePath("./node_modules"),
+    );
+    forbiddenPaths.serverSideScriptDirectories.push(
+      getInitializePath("./mods"),
+    );
+    process.cwd = () => "/usr/lib/mocksvrjs";
+    process.dirname = "/usr/lib/mocksvrjs";
+    process.filename = "/usr/lib/mocksvrjs/svr.js";
+  });
+
+  describe("getInitializePath", () => {
+    test("should return the correct path on Unix", () => {
+      os.platform.mockReturnValue("linux");
+      expect(getInitializePath("./config.json")).toBe("/config.json");
+    });
+
+    test("should return the correct path on Windows", () => {
+      process.cwd = () => "C:\\mocksvrjs";
+      process.dirname = "C:\\mocksvrjs";
+      process.filename = "C:\\mocksvrjs\\svr.js";
+      os.platform.mockReturnValue("win32");
+      expect(getInitializePath("./config.json")).toBe("/config.json");
+    });
+
+    test("should handle absolute paths on Unix", () => {
+      os.platform.mockReturnValue("linux");
+      expect(getInitializePath("/absolute/path")).toBe(
+        "/../../../absolute/path",
+      );
+    });
+
+    test("should handle absolute paths on Windows", () => {
+      process.cwd = () => "C:\\mocksvrjs";
+      process.dirname = "C:\\mocksvrjs";
+      process.filename = "C:\\mocksvrjs\\svr.js";
+      os.platform.mockReturnValue("win32");
+      expect(getInitializePath("C:\\absolute\\path")).toBe("/../absolute/path");
+    });
+
+    test("should handle relative paths on Unix", () => {
+      os.platform.mockReturnValue("linux");
+      expect(getInitializePath("./relative/path")).toBe("/relative/path");
+    });
+
+    test("should handle relative paths on Windows", () => {
+      process.cwd = () => "C:\\mocksvrjs";
+      process.dirname = "C:\\mocksvrjs";
+      process.filename = "C:\\mocksvrjs\\svr.js";
+      os.platform.mockReturnValue("win32");
+      expect(getInitializePath("./relative\\path")).toBe("/relative/path");
+    });
+  });
+
+  describe("isForbiddenPath", () => {
+    test("should return true if the path is forbidden", () => {
+      os.platform.mockReturnValue("linux");
+      expect(isForbiddenPath("/config.json", "config")).toBe(true);
+    });
+
+    test("should return false if the path is not forbidden", () => {
+      os.platform.mockReturnValue("linux");
+      expect(isForbiddenPath("/notconfig.json", "config")).toBe(false);
+    });
+
+    test("should handle case insensitivity on Windows", () => {
+      process.cwd = () => "C:\\mocksvrjs";
+      process.dirname = "C:\\mocksvrjs";
+      process.filename = "C:\\mocksvrjs\\svr.js";
+      os.platform.mockReturnValue("win32");
+      expect(isForbiddenPath("/CONFIG.JSON", "config")).toBe(true);
+    });
+
+    test("should handle array of forbidden paths", () => {
+      os.platform.mockReturnValue("linux");
+      expect(
+        isForbiddenPath("/node_modules", "serverSideScriptDirectories"),
+      ).toBe(true);
+      expect(isForbiddenPath("/mods", "serverSideScriptDirectories")).toBe(
+        true,
+      );
+      expect(
+        isForbiddenPath("/notforbidden", "serverSideScriptDirectories"),
+      ).toBe(false);
+    });
+  });
+
+  describe("isIndexOfForbiddenPath", () => {
+    test("should return true if the path is an index of a forbidden path", () => {
+      os.platform.mockReturnValue("linux");
+      expect(isIndexOfForbiddenPath("/config.json", "config")).toBe(true);
+      expect(
+        isIndexOfForbiddenPath("/node_modules/", "serverSideScriptDirectories"),
+      ).toBe(true);
+    });
+
+    test("should return false if the path is not an index of a forbidden path", () => {
+      os.platform.mockReturnValue("linux");
+      expect(isIndexOfForbiddenPath("/notconfig.json", "config")).toBe(false);
+      expect(
+        isIndexOfForbiddenPath("/notforbidden/", "serverSideScriptDirectories"),
+      ).toBe(false);
+    });
+
+    test("should handle case insensitivity on Windows", () => {
+      process.cwd = () => "C:\\mocksvrjs";
+      process.dirname = "C:\\mocksvrjs";
+      process.filename = "C:\\mocksvrjs\\svr.js";
+      os.platform.mockReturnValue("win32");
+      expect(isIndexOfForbiddenPath("/CONFIG.JSON", "config")).toBe(true);
+      expect(
+        isIndexOfForbiddenPath("/NODE_MODULES/", "serverSideScriptDirectories"),
+      ).toBe(true);
+    });
+
+    test("should handle array of forbidden paths", () => {
+      os.platform.mockReturnValue("linux");
+      expect(
+        isIndexOfForbiddenPath("/node_modules/", "serverSideScriptDirectories"),
+      ).toBe(true);
+      expect(
+        isIndexOfForbiddenPath("/mods/", "serverSideScriptDirectories"),
+      ).toBe(true);
+      expect(
+        isIndexOfForbiddenPath("/notforbidden/", "serverSideScriptDirectories"),
+      ).toBe(false);
+    });
+  });
+});