diff --git a/CHANGELOG.md b/CHANGELOG.md
index bce07f4..3fcc4bf 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,7 @@
 
 ## Unreleased
 
+- Tests: expand coverage for network helpers — `NetworkErrorMonitor` (record/dedupe/exclude/minStatus/assert), `interceptNetworkCall` (spy/fulfill/handler/method continue/non-JSON), plus `globToRegExp` / `responseMatchesFilter`
 - **Network interception / error monitor** — `interceptNetworkCall()`, `startNetworkErrorMonitor()` (see `docs/NETWORK.md`)
 - Docs: `docs/OUTLINE.md` checklist (update Outline QA & Dev Playkit page on each release); `docs/IDEAS.md` for OSS-borrowed backlog; adoption pause (no new consumer repos until soak)
 - CI: add tag-triggered `release` job (`.gitea/workflows/ci.yml`) — re-runs build/test, verifies tag matches `package.json` version and `CHANGELOG.md` documents it, creates a Gitea release with an `npm pack` tarball attached. Requires a one-time `GITEA_TOKEN` Actions secret.
diff --git a/src/browser/index.ts b/src/browser/index.ts
index 4747b94..99ad24a 100644
--- a/src/browser/index.ts
+++ b/src/browser/index.ts
@@ -19,6 +19,8 @@ export {
   NetworkErrorMonitor,
   matchesExcludePattern,
   dedupeNetworkErrors,
+  globToRegExp,
+  responseMatchesFilter,
   type FulfillResponse,
   type InterceptNetworkCallOptions,
   type InterceptedNetworkCall,
diff --git a/src/browser/network.test.ts b/src/browser/network.test.ts
index a162829..2cd8080 100644
--- a/src/browser/network.test.ts
+++ b/src/browser/network.test.ts
@@ -1,10 +1,75 @@
-import { describe, expect, it } from 'vitest';
+import { describe, expect, it, vi } from 'vitest';
+import type { Page, Request, Response, Route } from '@playwright/test';
 import {
   dedupeNetworkErrors,
+  globToRegExp,
+  interceptNetworkCall,
   matchesExcludePattern,
+  responseMatchesFilter,
+  startNetworkErrorMonitor,
   type NetworkError,
 } from './network.js';
 
+function mockRequest(overrides: {
+  method?: string;
+  url?: string;
+  postData?: string | null;
+} = {}): Request {
+  return {
+    method: () => overrides.method ?? 'GET',
+    url: () => overrides.url ?? 'https://example.com/api',
+    postData: () => overrides.postData ?? null,
+  } as unknown as Request;
+}
+
+function mockResponse(overrides: {
+  status?: number;
+  url?: string;
+  method?: string;
+  json?: unknown;
+  postData?: string | null;
+  jsonThrows?: boolean;
+}): Response {
+  const request = mockRequest({
+    method: overrides.method,
+    url: overrides.url,
+    postData: overrides.postData,
+  });
+  return {
+    status: () => overrides.status ?? 200,
+    url: () => overrides.url ?? 'https://example.com/api',
+    request: () => request,
+    json: async () => {
+      if (overrides.jsonThrows) throw new Error('not json');
+      return overrides.json ?? { ok: true };
+    },
+  } as unknown as Response;
+}
+
+type ResponseListener = (response: Response) => void;
+
+function createMockPage() {
+  const listeners = new Map<string, ResponseListener>();
+  const page = {
+    on: vi.fn((event: string, fn: ResponseListener) => {
+      listeners.set(event, fn);
+    }),
+    off: vi.fn((event: string, fn: ResponseListener) => {
+      if (listeners.get(event) === fn) listeners.delete(event);
+    }),
+    waitForResponse: vi.fn(),
+    route: vi.fn(async () => undefined),
+    unroute: vi.fn(async () => undefined),
+    emitResponse(response: Response) {
+      listeners.get('response')?.(response);
+    },
+    hasResponseListener() {
+      return listeners.has('response');
+    },
+  };
+  return page as typeof page & Page;
+}
+
 describe('matchesExcludePattern', () => {
   it('matches substring and regex', () => {
     expect(matchesExcludePattern('https://cdn.example.com/x.js', ['cdn.example.com'])).toBe(
@@ -15,6 +80,10 @@ describe('matchesExcludePattern', () => {
       false,
     );
   });
+
+  it('returns false for empty patterns', () => {
+    expect(matchesExcludePattern('https://example.com', [])).toBe(false);
+  });
 });
 
 describe('dedupeNetworkErrors', () => {
@@ -45,3 +114,211 @@ describe('dedupeNetworkErrors', () => {
     expect(out[1]?.status).toBe(404);
   });
 });
+
+describe('globToRegExp / responseMatchesFilter', () => {
+  it('matches Playwright-style globs', () => {
+    const re = globToRegExp('**/api/users');
+    expect('https://punimtagdev.levkin.ca/api/users').toMatch(re);
+    expect('https://punimtagdev.levkin.ca/api/posts').not.toMatch(re);
+    expect(globToRegExp('**/api/users/*').test('https://app/api/users/1')).toBe(true);
+  });
+
+  it('filters by url string glob and method', () => {
+    const getUsers = mockResponse({
+      url: 'https://app.example.com/api/users',
+      method: 'GET',
+      status: 200,
+    });
+    const postUsers = mockResponse({
+      url: 'https://app.example.com/api/users',
+      method: 'POST',
+      status: 201,
+    });
+    expect(responseMatchesFilter(getUsers, '**/api/users', 'GET')).toBe(true);
+    expect(responseMatchesFilter(postUsers, '**/api/users', 'GET')).toBe(false);
+    expect(responseMatchesFilter(postUsers, /\/api\/users$/, 'POST')).toBe(true);
+  });
+});
+
+describe('NetworkErrorMonitor', () => {
+  it('records 4xx/5xx, skips 2xx, and assertNoErrors throws', () => {
+    const page = createMockPage();
+    const net = startNetworkErrorMonitor(page);
+
+    page.emitResponse(mockResponse({ status: 200, url: 'https://app/ok' }));
+    page.emitResponse(mockResponse({ status: 500, url: 'https://app/boom', method: 'GET' }));
+    page.emitResponse(mockResponse({ status: 500, url: 'https://app/boom', method: 'GET' })); // dedupe
+    page.emitResponse(mockResponse({ status: 404, url: 'https://app/missing', method: 'GET' }));
+
+    expect(net.getErrors()).toHaveLength(2);
+    expect(() => net.assertNoErrors()).toThrow(/Network errors detected: 2/);
+    expect(page.hasResponseListener()).toBe(false); // stopped
+  });
+
+  it('assertNoErrors is a no-op when clean', () => {
+    const page = createMockPage();
+    const net = startNetworkErrorMonitor(page);
+    page.emitResponse(mockResponse({ status: 204, url: 'https://app/ok' }));
+    expect(() => net.assertNoErrors()).not.toThrow();
+  });
+
+  it('honors excludePatterns and minStatus', () => {
+    const page = createMockPage();
+    const net = startNetworkErrorMonitor(page, {
+      excludePatterns: ['sentry.io', /analytics\./],
+      minStatus: 500,
+    });
+
+    page.emitResponse(mockResponse({ status: 404, url: 'https://app/missing' })); // below min
+    page.emitResponse(mockResponse({ status: 500, url: 'https://sentry.io/api/1' })); // excluded
+    page.emitResponse(mockResponse({ status: 503, url: 'https://analytics.example.com/x' })); // excluded
+    page.emitResponse(mockResponse({ status: 502, url: 'https://app/fail' }));
+
+    expect(net.getErrors()).toEqual([
+      expect.objectContaining({ status: 502, url: 'https://app/fail' }),
+    ]);
+    net.stop();
+  });
+
+  it('stop() ignores further responses', () => {
+    const page = createMockPage();
+    const net = startNetworkErrorMonitor(page);
+    net.stop();
+    page.emitResponse(mockResponse({ status: 500, url: 'https://app/late' }));
+    expect(net.getErrors()).toHaveLength(0);
+  });
+});
+
+describe('interceptNetworkCall', () => {
+  it('spies on a matching response without installing a route', async () => {
+    const page = createMockPage();
+    const response = mockResponse({
+      status: 200,
+      url: 'https://app.example.com/api/users',
+      method: 'GET',
+      json: [{ id: 1 }],
+      postData: null,
+    });
+    page.waitForResponse.mockImplementation(async (pred: (r: Response) => boolean) => {
+      expect(pred(response)).toBe(true);
+      return response;
+    });
+
+    const result = await interceptNetworkCall({
+      page,
+      url: '**/api/users',
+      method: 'GET',
+    });
+
+    expect(page.route).not.toHaveBeenCalled();
+    expect(page.unroute).not.toHaveBeenCalled();
+    expect(result.status).toBe(200);
+    expect(result.responseJson).toEqual([{ id: 1 }]);
+    expect(result.requestJson).toBeUndefined();
+  });
+
+  it('installs fulfill route and unroutes in finally', async () => {
+    const page = createMockPage();
+    const response = mockResponse({
+      status: 200,
+      url: 'https://app.example.com/api/users',
+      method: 'GET',
+      json: [{ id: 9, name: 'stub' }],
+    });
+    page.waitForResponse.mockResolvedValue(response);
+    page.route.mockImplementation(async (_url: string | RegExp, handler: (route: Route, request: Request) => Promise<void>) => {
+      const route = {
+        continue: vi.fn(async () => undefined),
+        fulfill: vi.fn(async () => undefined),
+      } as unknown as Route;
+      await handler(route, mockRequest({ method: 'GET', url: response.url() }));
+      expect(route.fulfill).toHaveBeenCalledWith(
+        expect.objectContaining({
+          status: 200,
+          body: JSON.stringify([{ id: 9, name: 'stub' }]),
+        }),
+      );
+    });
+
+    const result = await interceptNetworkCall({
+      page,
+      url: '**/api/users',
+      fulfillResponse: { status: 200, body: [{ id: 9, name: 'stub' }] },
+    });
+
+    expect(page.route).toHaveBeenCalledOnce();
+    expect(page.unroute).toHaveBeenCalledOnce();
+    expect(result.responseJson).toEqual([{ id: 9, name: 'stub' }]);
+  });
+
+  it('uses custom handler and parses request JSON', async () => {
+    const page = createMockPage();
+    const response = mockResponse({
+      status: 401,
+      url: 'https://app.example.com/api/login',
+      method: 'POST',
+      json: { error: 'nope' },
+      postData: JSON.stringify({ user: 'e2e' }),
+    });
+    page.waitForResponse.mockResolvedValue(response);
+    const handler = vi.fn(async (route: Route) => {
+      await route.fulfill({ status: 401, body: '{"error":"nope"}' });
+    });
+    page.route.mockImplementation(async (_url, routeHandler) => {
+      const route = {
+        continue: vi.fn(),
+        fulfill: vi.fn(async () => undefined),
+      } as unknown as Route;
+      await routeHandler(route, mockRequest({ method: 'POST', postData: '{"user":"e2e"}' }));
+    });
+
+    const result = await interceptNetworkCall({
+      page,
+      url: /\/api\/login$/,
+      method: 'POST',
+      handler,
+    });
+
+    expect(handler).toHaveBeenCalledOnce();
+    expect(result.status).toBe(401);
+    expect(result.requestJson).toEqual({ user: 'e2e' });
+    expect(result.responseJson).toEqual({ error: 'nope' });
+  });
+
+  it('tolerates non-JSON response bodies', async () => {
+    const page = createMockPage();
+    const response = mockResponse({
+      status: 200,
+      url: 'https://app.example.com/health',
+      jsonThrows: true,
+    });
+    page.waitForResponse.mockResolvedValue(response);
+
+    const result = await interceptNetworkCall({ page, url: '**/health' });
+    expect(result.status).toBe(200);
+    expect(result.responseJson).toBeUndefined();
+  });
+
+  it('continues non-matching method on fulfill route', async () => {
+    const page = createMockPage();
+    const response = mockResponse({
+      status: 200,
+      url: 'https://app.example.com/api/users',
+      method: 'GET',
+    });
+    page.waitForResponse.mockResolvedValue(response);
+    const continueFn = vi.fn(async () => undefined);
+    page.route.mockImplementation(async (_url, routeHandler) => {
+      const route = { continue: continueFn, fulfill: vi.fn() } as unknown as Route;
+      await routeHandler(route, mockRequest({ method: 'OPTIONS' }));
+    });
+
+    await interceptNetworkCall({
+      page,
+      url: '**/api/users',
+      method: 'GET',
+      fulfillResponse: { body: [] },
+    });
+    expect(continueFn).toHaveBeenCalledOnce();
+  });
+});
diff --git a/src/browser/network.ts b/src/browser/network.ts
index 54f4fbc..5cd22fe 100644
--- a/src/browser/network.ts
+++ b/src/browser/network.ts
@@ -50,21 +50,25 @@ async function parseJsonSafe(raw: string | null): Promise<unknown> {
   }
 }
 
-function responsePredicate(
+/** Convert a Playwright-style glob to a RegExp (exported for unit tests). */
+export function globToRegExp(pattern: string): RegExp {
+  const escaped = pattern
+    .replace(/[.+^${}()|[\]\\]/g, '\\$&')
+    .replace(/\*\*/g, '.*')
+    .replace(/\*/g, '[^/?]*');
+  return new RegExp(escaped);
+}
+
+/** True when a response matches URL + optional method filters (exported for unit tests). */
+export function responseMatchesFilter(
   response: Response,
   url: string | RegExp,
   method?: string,
 ): boolean {
   if (!methodMatches(response.request(), method)) return false;
   if (url instanceof RegExp) return url.test(response.url());
-  // Prefer Playwright's built-in glob matching when possible via URL string compare.
   try {
-    return response.url().match(new RegExp(
-      url
-        .replace(/[.+^${}()|[\]\\]/g, '\\$&')
-        .replace(/\*\*/g, '.*')
-        .replace(/\*/g, '[^/?]*'),
-    )) !== null;
+    return response.url().match(globToRegExp(url)) !== null;
   } catch {
     return response.url().includes(String(url));
   }
@@ -89,7 +93,7 @@ export function interceptNetworkCall(
 
   // Register the response waiter first so we never miss a fast request.
   const responsePromise = page.waitForResponse(
-    (res) => responsePredicate(res, url, method),
+    (res) => responseMatchesFilter(res, url, method),
     { timeout },
   );
 
diff --git a/src/index.ts b/src/index.ts
index 09b2945..4786a11 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -27,6 +27,8 @@ export {
   NetworkErrorMonitor,
   matchesExcludePattern,
   dedupeNetworkErrors,
+  globToRegExp,
+  responseMatchesFilter,
   type ClickOptions,
   type FillOptions,
   type GotoOptions,