diff --git a/tests/nostr/countDiagnostics.test.mjs b/tests/nostr/countDiagnostics.test.mjs
new file mode 100644
index 00000000..f8ec0b4f
--- /dev/null
+++ b/tests/nostr/countDiagnostics.test.mjs
@@ -0,0 +1,159 @@
+import { describe, it, before, after, beforeEach } from "node:test";
+import assert from "node:assert/strict";
+import "../test-setup.mjs";
+
+// Setup globals before importing any module
+globalThis.__BITVID_DEV_MODE_OVERRIDE__ = true;
+globalThis.__BITVID_VERBOSE_DEV_MODE_OVERRIDE__ = false;
+
+// Mock console.warn BEFORE importing logger so consoleAdapter binds to our mock
+let warnCalls = [];
+const originalConsoleWarn = console.warn;
+console.warn = (...args) => {
+  warnCalls.push(args);
+};
+
+// Force initial import to ensure logger binds to our mock
+await import("../../js/nostr/countDiagnostics.js");
+
+describe("countDiagnostics", () => {
+  let countDiagnosticsModule;
+
+  after(() => {
+    console.warn = originalConsoleWarn;
+  });
+
+  beforeEach(async () => {
+    warnCalls = [];
+    window.__BITVID_VERBOSE_DEV_MODE__ = undefined;
+
+    // Reload module to get fresh state (empty seenWarningKeys)
+    // Use unique timestamp to bust module cache
+    // Note: This relies on Node.js module caching behavior where query params create new module instances
+    countDiagnosticsModule = await import(`../../js/nostr/countDiagnostics.js?t=${Date.now()}-${Math.random()}`);
+  });
+
+  describe("isVerboseDiagnosticsEnabled", () => {
+    it("should return false by default (when override is false and window flag is undefined)", () => {
+      assert.equal(countDiagnosticsModule.isVerboseDiagnosticsEnabled(), false);
+    });
+
+    it("should return true when window.__BITVID_VERBOSE_DEV_MODE__ is true", () => {
+      window.__BITVID_VERBOSE_DEV_MODE__ = true;
+      assert.equal(countDiagnosticsModule.isVerboseDiagnosticsEnabled(), true);
+    });
+
+    it("should return false when window.__BITVID_VERBOSE_DEV_MODE__ is false", () => {
+      window.__BITVID_VERBOSE_DEV_MODE__ = false;
+      assert.equal(countDiagnosticsModule.isVerboseDiagnosticsEnabled(), false);
+    });
+
+    it("should fallback to config default if window flag is not boolean", () => {
+      window.__BITVID_VERBOSE_DEV_MODE__ = "invalid";
+      assert.equal(countDiagnosticsModule.isVerboseDiagnosticsEnabled(), false);
+    });
+  });
+
+  describe("Logging Functions", () => {
+    it("should NOT log when verbose mode is disabled", () => {
+      window.__BITVID_VERBOSE_DEV_MODE__ = false;
+      const {
+        logCountTimeoutCleanupFailure,
+        logRelayCountFailure,
+        logRebroadcastCountFailure,
+        logViewCountFailure
+      } = countDiagnosticsModule;
+
+      logCountTimeoutCleanupFailure(new Error("test error"));
+      logRelayCountFailure("wss://relay1.com", new Error("test error"));
+      logRebroadcastCountFailure(new Error("test error"));
+      logViewCountFailure(new Error("test error"));
+
+      assert.equal(warnCalls.length, 0, "Should not log when verbose mode is disabled");
+    });
+
+    it("should log when verbose mode is enabled", () => {
+      window.__BITVID_VERBOSE_DEV_MODE__ = true;
+      const {
+        logCountTimeoutCleanupFailure,
+        logRelayCountFailure,
+        logRebroadcastCountFailure,
+        logViewCountFailure
+      } = countDiagnosticsModule;
+
+      // 1. logCountTimeoutCleanupFailure
+      logCountTimeoutCleanupFailure(new Error("cleanup error"));
+      assert.equal(warnCalls.length, 1);
+      assert.match(warnCalls[0][0], /cleanup failed/);
+
+      // 2. logRelayCountFailure
+      logRelayCountFailure("wss://relay-enabled.com", new Error("relay error"));
+      assert.equal(warnCalls.length, 2);
+      assert.match(warnCalls[1][0], /request failed on wss:\/\/relay-enabled\.com/);
+
+      // 3. logRebroadcastCountFailure
+      logRebroadcastCountFailure(new Error("rebroadcast error"));
+      assert.equal(warnCalls.length, 3);
+      assert.match(warnCalls[2][0], /rebroadcast failed/);
+
+      // 4. logViewCountFailure
+      logViewCountFailure(new Error("view error"));
+      assert.equal(warnCalls.length, 4);
+      assert.match(warnCalls[3][0], /view request failed/);
+    });
+
+    it("should throttle repeated logs", () => {
+      window.__BITVID_VERBOSE_DEV_MODE__ = true;
+      const {
+        logCountTimeoutCleanupFailure,
+        logRelayCountFailure,
+        logRebroadcastCountFailure,
+        logViewCountFailure
+      } = countDiagnosticsModule;
+
+      // First calls should log
+      logCountTimeoutCleanupFailure(new Error("cleanup error"));
+      logRelayCountFailure("wss://relay-throttled.com", new Error("relay error"));
+      logRebroadcastCountFailure(new Error("rebroadcast error"));
+      logViewCountFailure(new Error("view error"));
+
+      assert.equal(warnCalls.length, 4, "Initial calls should log");
+      const initialLogs = [...warnCalls];
+      warnCalls = []; // Clear log buffer
+
+      // Repeated calls should throttle
+      logCountTimeoutCleanupFailure(new Error("cleanup error again"));
+      logRelayCountFailure("wss://relay-throttled.com", new Error("relay error again"));
+      logRebroadcastCountFailure(new Error("rebroadcast error again"));
+      logViewCountFailure(new Error("view error again"));
+
+      assert.equal(warnCalls.length, 0, "Repeated calls should be throttled");
+    });
+
+    it("should log distinct relay failures separately (different keys)", () => {
+      window.__BITVID_VERBOSE_DEV_MODE__ = true;
+      const { logRelayCountFailure } = countDiagnosticsModule;
+
+      logRelayCountFailure("wss://relay-1.com", new Error("relay error 1"));
+      assert.equal(warnCalls.length, 1);
+      assert.match(warnCalls[0][0], /wss:\/\/relay-1\.com/);
+
+      warnCalls = [];
+      logRelayCountFailure("wss://relay-2.com", new Error("relay error 2"));
+      assert.equal(warnCalls.length, 1);
+      assert.match(warnCalls[0][0], /wss:\/\/relay-2\.com/);
+    });
+
+    it("should suppress 'Failed to connect to relay' errors", () => {
+      window.__BITVID_VERBOSE_DEV_MODE__ = true;
+      const { logRelayCountFailure } = countDiagnosticsModule;
+
+      logRelayCountFailure("wss://relay-fail.com", new Error("Failed to connect to relay wss://relay-fail.com"));
+      assert.equal(warnCalls.length, 0, "Should suppress connection errors");
+
+      // Also test with object that has message
+      logRelayCountFailure("wss://relay-fail-obj.com", { message: "Failed to connect to relay wss://relay-fail-obj.com" });
+      assert.equal(warnCalls.length, 0, "Should suppress connection errors (object)");
+    });
+  });
+});