diff --git a/src/lib/scrub.test.ts b/src/lib/scrub.test.ts
new file mode 100644
index 0000000..30b2b65
--- /dev/null
+++ b/src/lib/scrub.test.ts
@@ -0,0 +1,105 @@
+import { test } from "node:test"
+import assert from "node:assert/strict"
+import { scrubUrl, scrubString, scrubObject } from "./scrub.ts"
+
+// scrubUrl ----------------------------------------------------------------
+
+test("scrubUrl: strips basic-auth credentials", () => {
+  assert.equal(
+    scrubUrl("https://user:secret@host.com/path"),
+    "https://<redacted>@host.com/path",
+  )
+})
+
+test("scrubUrl: redacts ?token= query param", () => {
+  assert.equal(
+    scrubUrl("https://host.com/api?token=abc123"),
+    "https://host.com/api?token=<redacted>",
+  )
+})
+
+test("scrubUrl: redacts ?api_key= query param", () => {
+  assert.equal(
+    scrubUrl("https://host.com/api?api_key=xyz"),
+    "https://host.com/api?api_key=<redacted>",
+  )
+})
+
+test("scrubUrl: redacts ?password= query param", () => {
+  assert.equal(
+    scrubUrl("https://host.com/login?password=hunter2"),
+    "https://host.com/login?password=<redacted>",
+  )
+})
+
+test("scrubUrl: redacts ?access_token= query param", () => {
+  assert.equal(
+    scrubUrl("https://host.com/api?access_token=tok_secret"),
+    "https://host.com/api?access_token=<redacted>",
+  )
+})
+
+test("scrubUrl: leaves clean URL unchanged", () => {
+  const clean = "http://100.108.64.76:4096/session"
+  assert.equal(scrubUrl(clean), clean)
+})
+
+test("scrubUrl: redacts only secret params, leaves others intact", () => {
+  const result = scrubUrl("https://host.com/api?foo=bar&token=secret&baz=qux")
+  assert.equal(result, "https://host.com/api?foo=bar&token=<redacted>&baz=qux")
+})
+
+// scrubString -------------------------------------------------------------
+
+test("scrubString: replaces credentials in a URL embedded in a message", () => {
+  const msg = "fetch failed: https://admin:pass@myserver.com/api"
+  const result = scrubString(msg)
+  assert.ok(result.includes("<redacted>"), "should contain <redacted>")
+  assert.ok(!result.includes("admin"), "should not contain username")
+  assert.ok(!result.includes("pass"), "should not contain password")
+})
+
+test("scrubString: redacts token query param inside a message", () => {
+  const msg = "request to https://api.example.com/data?token=s3cr3t failed"
+  const result = scrubString(msg)
+  assert.ok(result.includes("token=<redacted>"), "token should be redacted")
+  assert.ok(!result.includes("s3cr3t"), "secret value should be gone")
+})
+
+test("scrubString: leaves plain strings without URLs unchanged", () => {
+  const plain = "something went wrong during connection"
+  assert.equal(scrubString(plain), plain)
+})
+
+// scrubObject -------------------------------------------------------------
+
+test("scrubObject: scrubs string values containing URLs", () => {
+  const obj = { url: "https://user:pw@host.com/path" }
+  const result = scrubObject(obj)
+  assert.ok((result.url as string).includes("<redacted>"))
+  assert.ok(!(result.url as string).includes("pw"))
+})
+
+test("scrubObject: recursively scrubs nested objects", () => {
+  const obj = {
+    outer: "clean",
+    inner: {
+      url: "https://host.com/api?token=secret",
+      label: "safe text",
+    },
+  }
+  const result = scrubObject(obj)
+  const inner = result.inner as Record<string, unknown>
+  assert.equal(inner.url, "https://host.com/api?token=<redacted>")
+  assert.equal(inner.label, "safe text")
+  assert.equal(result.outer, "clean")
+})
+
+test("scrubObject: preserves non-string, non-object values as-is", () => {
+  const obj = { count: 42, flag: true, items: [1, 2, 3], nothing: null }
+  const result = scrubObject(obj as Record<string, unknown>)
+  assert.equal(result.count, 42)
+  assert.equal(result.flag, true)
+  assert.deepEqual(result.items, [1, 2, 3])
+  assert.equal(result.nothing, null)
+})
diff --git a/src/lib/scrub.ts b/src/lib/scrub.ts
new file mode 100644
index 0000000..b75038e
--- /dev/null
+++ b/src/lib/scrub.ts
@@ -0,0 +1,26 @@
+// Pure URL/string scrubbing utilities — no React Native or Sentry deps.
+// Extracted here so they can be unit-tested with plain `node --test`.
+
+// Strip basic-auth credentials and any `?token=` style query secrets so URLs
+// can be safely sent or logged.
+export function scrubUrl(url: string): string {
+  return url
+    .replace(/\/\/[^@/]+@/, "//<redacted>@")
+    .replace(/([?&](?:token|access_token|api_key|key|password|pwd|auth)=)[^&#]*/gi, "$1<redacted>")
+}
+
+export function scrubString(s: string): string {
+  // Catch any embedded URL inside a free-text string (error messages often
+  // contain them, e.g. "fetch failed: https://user:pw@host/...").
+  return s.replace(/https?:\/\/\S+/g, (m) => scrubUrl(m))
+}
+
+export function scrubObject(obj: Record<string, unknown>): Record<string, unknown> {
+  const out: Record<string, unknown> = {}
+  for (const [k, v] of Object.entries(obj)) {
+    if (typeof v === "string") out[k] = scrubString(v)
+    else if (v && typeof v === "object" && !Array.isArray(v)) out[k] = scrubObject(v as Record<string, unknown>)
+    else out[k] = v
+  }
+  return out
+}
diff --git a/src/lib/sentry.ts b/src/lib/sentry.ts
index 9fef1a2..015f3a1 100644
--- a/src/lib/sentry.ts
+++ b/src/lib/sentry.ts
@@ -13,6 +13,7 @@ import * as Sentry from "@sentry/react-native"
 import appJson from "../../app.json"
 import { log } from "./logbuffer"
 import type { DiagnosticReport } from "./diagnostics"
+import { scrubUrl, scrubString, scrubObject } from "./scrub"
 
 const DSN = process.env.EXPO_PUBLIC_SENTRY_DSN
 const APP_VERSION = (appJson as { expo?: { version?: string } }).expo?.version ?? "unknown"
@@ -124,31 +125,9 @@ function toError(value: unknown): Error {
   }
 }
 
-// --- Scrubbing -----------------------------------------------------------
+// --- Scrubbing (pure functions live in ./scrub for testability) ----------
 
-// Strip basic-auth credentials and any `?token=` style query secrets so URLs
-// can be safely sent or logged.
-export function scrubUrl(url: string): string {
-  return url
-    .replace(/\/\/[^@/]+@/, "//<redacted>@")
-    .replace(/([?&](?:token|access_token|api_key|key|password|pwd|auth)=)[^&#]*/gi, "$1<redacted>")
-}
-
-function scrubString(s: string): string {
-  // Catch any embedded URL inside a free-text string (error messages often
-  // contain them, e.g. "fetch failed: https://user:pw@host/...").
-  return s.replace(/https?:\/\/\S+/g, (m) => scrubUrl(m))
-}
-
-function scrubObject(obj: Record<string, unknown>): Record<string, unknown> {
-  const out: Record<string, unknown> = {}
-  for (const [k, v] of Object.entries(obj)) {
-    if (typeof v === "string") out[k] = scrubString(v)
-    else if (v && typeof v === "object" && !Array.isArray(v)) out[k] = scrubObject(v as Record<string, unknown>)
-    else out[k] = v
-  }
-  return out
-}
+export { scrubUrl } from "./scrub"
 
 function scrubEvent<T extends Sentry.Event>(event: T): T {
   if (event.request?.url) event.request.url = scrubUrl(event.request.url)