diff --git a/src/reporter/src/components/dashboard/dashboard-filters.jsx b/src/reporter/src/components/dashboard/dashboard-filters.jsx
index 10ac3800..11d4a608 100644
--- a/src/reporter/src/components/dashboard/dashboard-filters.jsx
+++ b/src/reporter/src/components/dashboard/dashboard-filters.jsx
@@ -25,14 +25,8 @@ function getDeviceIcon(width) {
   return ComputerDesktopIcon;
 }
 
-/**
- * Get device label for viewport
- */
-function _getDeviceLabel(viewportStr) {
-  let width = parseInt(viewportStr.split('×')[0], 10);
-  if (width <= 480) return 'Mobile';
-  if (width <= 1024) return 'Tablet';
-  return 'Desktop';
+function getViewportWidth(viewport) {
+  return Number(viewport.split('×')[0]);
 }
 
 /**
@@ -299,7 +293,7 @@ export default function DashboardFilters({
 
   // Render viewport option with device icon
   let renderViewportOption = useCallback(viewport => {
-    let DeviceIcon = getDeviceIcon(parseInt(viewport.split('×')[0], 10));
+    let DeviceIcon = getDeviceIcon(getViewportWidth(viewport));
     return (
       <>
         <DeviceIcon className="w-4 h-4 text-slate-400" />
@@ -313,7 +307,7 @@ export default function DashboardFilters({
     if (value === 'all') {
       return <span className="text-slate-400">All viewports</span>;
     }
-    let DeviceIcon = getDeviceIcon(parseInt(value.split('×')[0], 10));
+    let DeviceIcon = getDeviceIcon(getViewportWidth(value));
     return (
       <span className="flex items-center gap-2">
         <DeviceIcon className="w-4 h-4 text-slate-400" />
@@ -553,7 +547,7 @@ export default function DashboardFilters({
           {selectedViewport !== 'all' && (
             <ActiveFilter
               label={selectedViewport}
-              icon={getDeviceIcon(parseInt(selectedViewport.split('×')[0], 10))}
+              icon={getDeviceIcon(getViewportWidth(selectedViewport))}
               onRemove={() => setSelectedViewport('all')}
             />
           )}
diff --git a/src/server/routers/events.js b/src/server/routers/events.js
index 97fda285..e15ce07e 100644
--- a/src/server/routers/events.js
+++ b/src/server/routers/events.js
@@ -11,130 +11,207 @@ let FILE_POLL_INTERVAL_MS = 50;
 let REPORT_READ_RETRY_MS = 25;
 let MAX_REPORT_READ_RETRIES = 3;
 
+let defaultTimers = {
+  setTimeout,
+  clearTimeout,
+  setInterval,
+  clearInterval,
+};
+
 /**
- * Create events router for SSE
- * @param {Object} context - Router context
- * @param {string} context.workingDir - Working directory for report data
- * @returns {Function} Route handler
+ * Read and parse JSON from disk, returning null on missing or invalid files.
  */
-export function createEventsRouter(context) {
-  const { workingDir = process.cwd() } = context || {};
-  const reportDataPath = join(workingDir, '.vizzly', 'report-data.json');
-  const baselineMetadataPath = join(
-    workingDir,
-    '.vizzly',
-    'baselines',
-    'metadata.json'
-  );
+export function readJsonFile(path) {
+  if (!existsSync(path)) {
+    return null;
+  }
 
-  /**
-   * Read and parse baseline metadata, returning null on error
-   */
-  const readBaselineMetadata = () => {
-    if (!existsSync(baselineMetadataPath)) {
-      return null;
-    }
-    try {
-      return JSON.parse(readFileSync(baselineMetadataPath, 'utf8'));
-    } catch {
-      return null;
-    }
-  };
+  try {
+    return JSON.parse(readFileSync(path, 'utf8'));
+  } catch {
+    return null;
+  }
+}
 
-  /**
-   * Read and parse report data with baseline metadata included
-   */
-  const readReportData = () => {
-    if (!existsSync(reportDataPath)) {
-      return null;
-    }
-    try {
-      const data = JSON.parse(readFileSync(reportDataPath, 'utf8'));
-      // Include baseline metadata for stats view
-      data.baseline = readBaselineMetadata();
-      return data;
-    } catch {
-      return null;
-    }
-  };
+/**
+ * Read report data and attach baseline metadata for the stats view.
+ */
+export function readReportDataFile({ reportDataPath, baselineMetadataPath }) {
+  let data = readJsonFile(reportDataPath);
+  if (!data) {
+    return null;
+  }
 
-  /**
-   * Send SSE event to response
-   */
-  const sendEvent = (res, eventType, data) => {
-    if (res.writableEnded) return;
-    res.write(`event: ${eventType}\n`);
-    res.write(`data: ${JSON.stringify(data)}\n\n`);
+  return {
+    ...data,
+    baseline: readJsonFile(baselineMetadataPath),
   };
+}
 
-  /**
-   * Build a lookup map from comparisons array keyed by id
-   */
-  const buildComparisonMap = comparisons => {
-    let map = new Map();
-    for (let c of comparisons) {
-      map.set(c.id, c);
+/**
+ * Build a lookup map from comparisons array keyed by id
+ */
+function buildComparisonMap(comparisons) {
+  let map = new Map();
+  for (let c of comparisons) {
+    map.set(c.id, c);
+  }
+  return map;
+}
+
+function comparisonChanged(oldComp, newComp) {
+  return JSON.stringify(oldComp) !== JSON.stringify(newComp);
+}
+
+/**
+ * Extract summary fields (everything except comparisons) for diffing
+ */
+function extractSummary(data) {
+  let { comparisons: _c, ...summary } = data;
+  return summary;
+}
+
+/**
+ * Check if summary-level fields changed between old and new data
+ */
+function summaryChanged(oldData, newData) {
+  let oldSummary = extractSummary(oldData);
+  let newSummary = extractSummary(newData);
+  return JSON.stringify(oldSummary) !== JSON.stringify(newSummary);
+}
+
+/**
+ * Build incremental SSE events by diffing old vs new report data.
+ */
+export function buildReportDataEvents(oldData, newData) {
+  if (!oldData) {
+    return [{ type: 'reportData', data: newData }];
+  }
+
+  let events = [];
+  let oldComparisons = oldData.comparisons || [];
+  let newComparisons = newData.comparisons || [];
+
+  let oldMap = buildComparisonMap(oldComparisons);
+  let newMap = buildComparisonMap(newComparisons);
+
+  // New or changed comparisons send the full comparison object, not a partial delta.
+  for (let [id, newComp] of newMap) {
+    let oldComp = oldMap.get(id);
+    if (!oldComp || comparisonChanged(oldComp, newComp)) {
+      events.push({ type: 'comparisonUpdate', data: newComp });
     }
-    return map;
-  };
+  }
 
-  const comparisonChanged = (oldComp, newComp) => {
-    return JSON.stringify(oldComp) !== JSON.stringify(newComp);
-  };
+  for (let [id] of oldMap) {
+    if (!newMap.has(id)) {
+      events.push({ type: 'comparisonRemoved', data: { id } });
+    }
+  }
 
-  /**
-   * Extract summary fields (everything except comparisons) for diffing
-   */
-  const extractSummary = data => {
-    let { comparisons: _c, ...summary } = data;
-    return summary;
-  };
+  if (summaryChanged(oldData, newData)) {
+    events.push({ type: 'summaryUpdate', data: extractSummary(newData) });
+  }
 
-  /**
-   * Check if summary-level fields changed between old and new data
-   */
-  const summaryChanged = (oldData, newData) => {
-    let oldSummary = extractSummary(oldData);
-    let newSummary = extractSummary(newData);
-    return JSON.stringify(oldSummary) !== JSON.stringify(newSummary);
-  };
+  return events;
+}
 
-  /**
-   * Send incremental updates by diffing old vs new report data.
-   * Returns true if any events were sent.
-   */
-  const sendIncrementalUpdates = (res, oldData, newData) => {
-    let sent = false;
-    let oldComparisons = oldData.comparisons || [];
-    let newComparisons = newData.comparisons || [];
-
-    let oldMap = buildComparisonMap(oldComparisons);
-    let newMap = buildComparisonMap(newComparisons);
-
-    // New or changed comparisons — sends the full comparison object, not a partial delta
-    for (let [id, newComp] of newMap) {
-      let oldComp = oldMap.get(id);
-      if (!oldComp || comparisonChanged(oldComp, newComp)) {
-        sendEvent(res, 'comparisonUpdate', newComp);
-        sent = true;
-      }
+/**
+ * Watch report-data.json with fs.watch plus a lightweight mtime fallback.
+ */
+export function watchReportDataFile({
+  workingDir,
+  reportDataPath,
+  onReportDataChanged,
+  timers = defaultTimers,
+}) {
+  let watcher = null;
+  let filePollInterval = null;
+  let vizzlyDir = join(workingDir, '.vizzly');
+
+  if (existsSync(vizzlyDir)) {
+    try {
+      watcher = watch(
+        vizzlyDir,
+        { recursive: false },
+        (_eventType, filename) => {
+          // Some platforms occasionally omit the filename for directory watch
+          // events. In that case, fall back to re-reading report data.
+          if (!filename || filename === 'report-data.json') {
+            onReportDataChanged();
+          }
+        }
+      );
+      watcher.on('error', () => {
+        if (watcher) {
+          watcher.close();
+          watcher = null;
+        }
+      });
+    } catch {
+      // File watching not available, mtime polling remains as fallback.
     }
+  }
 
-    // Removed comparisons
-    for (let [id] of oldMap) {
-      if (!newMap.has(id)) {
-        sendEvent(res, 'comparisonRemoved', { id });
-        sent = true;
+  let lastPolledMtime = existsSync(reportDataPath)
+    ? statSync(reportDataPath).mtimeMs
+    : null;
+
+  filePollInterval = timers.setInterval(() => {
+    let nextMtime = null;
+    if (existsSync(reportDataPath)) {
+      try {
+        nextMtime = statSync(reportDataPath).mtimeMs;
+      } catch {
+        nextMtime = null;
       }
     }
+    if (nextMtime !== lastPolledMtime) {
+      lastPolledMtime = nextMtime;
+      onReportDataChanged();
+    }
+  }, FILE_POLL_INTERVAL_MS);
 
-    // Summary-level changes (total, passed, failed, etc.)
-    if (summaryChanged(oldData, newData)) {
-      sendEvent(res, 'summaryUpdate', extractSummary(newData));
-      sent = true;
+  return () => {
+    if (watcher) {
+      watcher.close();
+      watcher = null;
     }
+    if (filePollInterval) {
+      timers.clearInterval(filePollInterval);
+      filePollInterval = null;
+    }
+  };
+}
 
-    return sent;
+/**
+ * Create events router for SSE
+ * @param {Object} context - Router context
+ * @param {string} context.workingDir - Working directory for report data
+ * @returns {Function} Route handler
+ */
+export function createEventsRouter(context) {
+  let {
+    workingDir = process.cwd(),
+    readReportData = readReportDataFile,
+    watchReportData = watchReportDataFile,
+    timers = defaultTimers,
+  } = context || {};
+  let reportDataPath = join(workingDir, '.vizzly', 'report-data.json');
+  let baselineMetadataPath = join(
+    workingDir,
+    '.vizzly',
+    'baselines',
+    'metadata.json'
+  );
+
+  /**
+   * Send SSE event to response
+   */
+  let sendEvent = (res, eventType, data) => {
+    if (res.writableEnded) return;
+    res.write(`event: ${eventType}\n`);
+    res.write(`data: ${JSON.stringify(data)}\n\n`);
   };
 
   return async function handleEventsRoute(req, res, pathname) {
@@ -151,30 +228,28 @@ export function createEventsRouter(context) {
     });
 
     // Send initial full data immediately
-    let lastSentData = readReportData();
+    let lastSentData = readReportData({ reportDataPath, baselineMetadataPath });
     if (lastSentData) {
       sendEvent(res, 'reportData', lastSentData);
     }
 
     // Debounce file change events (fs.watch can fire multiple times)
     let debounceTimer = null;
-    let watcher = null;
-    let filePollInterval = null;
 
-    const scheduleUpdate = () => {
+    let scheduleUpdate = () => {
       if (debounceTimer) {
-        clearTimeout(debounceTimer);
+        timers.clearTimeout(debounceTimer);
       }
-      debounceTimer = setTimeout(sendUpdate, FILE_WATCH_DEBOUNCE_MS);
+      debounceTimer = timers.setTimeout(sendUpdate, FILE_WATCH_DEBOUNCE_MS);
     };
-    const sendUpdate = (retryCount = 0) => {
-      const newData = readReportData();
+    let sendUpdate = (retryCount = 0) => {
+      let newData = readReportData({ reportDataPath, baselineMetadataPath });
       if (!newData) {
         if (
           existsSync(reportDataPath) &&
           retryCount < MAX_REPORT_READ_RETRIES
         ) {
-          debounceTimer = setTimeout(
+          debounceTimer = timers.setTimeout(
             () => sendUpdate(retryCount + 1),
             REPORT_READ_RETRY_MS
           );
@@ -182,84 +257,39 @@ export function createEventsRouter(context) {
         return;
       }
 
-      if (!lastSentData) {
-        // No previous data — send full payload
-        sendEvent(res, 'reportData', newData);
-      } else {
-        // Diff and send incremental updates
-        let sent = sendIncrementalUpdates(res, lastSentData, newData);
-        // If nothing changed, skip (no event needed)
-        if (!sent) return;
+      let events = buildReportDataEvents(lastSentData, newData);
+      if (events.length === 0) {
+        return;
       }
-      lastSentData = newData;
-    };
 
-    // Watch for file changes
-    const vizzlyDir = join(workingDir, '.vizzly');
-    if (existsSync(vizzlyDir)) {
-      try {
-        watcher = watch(
-          vizzlyDir,
-          { recursive: false },
-          (_eventType, filename) => {
-            // Some platforms occasionally omit the filename for directory watch
-            // events. In that case, fall back to re-reading report data.
-            if (!filename || filename === 'report-data.json') {
-              scheduleUpdate();
-            }
-          }
-        );
-        watcher.on('error', () => {
-          if (watcher) {
-            watcher.close();
-            watcher = null;
-          }
-        });
-      } catch {
-        // File watching not available, client will fall back to polling
+      for (let event of events) {
+        sendEvent(res, event.type, event.data);
       }
-    }
+      lastSentData = newData;
+    };
 
-    let lastPolledMtime = existsSync(reportDataPath)
-      ? statSync(reportDataPath).mtimeMs
-      : null;
-    filePollInterval = setInterval(() => {
-      let nextMtime = null;
-      if (existsSync(reportDataPath)) {
-        try {
-          nextMtime = statSync(reportDataPath).mtimeMs;
-        } catch {
-          nextMtime = null;
-        }
-      }
-      if (nextMtime !== lastPolledMtime) {
-        lastPolledMtime = nextMtime;
-        scheduleUpdate();
-      }
-    }, FILE_POLL_INTERVAL_MS);
+    let cleanupReportWatcher = watchReportData({
+      workingDir,
+      reportDataPath,
+      onReportDataChanged: scheduleUpdate,
+      timers,
+    });
 
     // Heartbeat to keep connection alive (every 30 seconds)
-    const heartbeatInterval = setInterval(() => {
+    let heartbeatInterval = timers.setInterval(() => {
       if (!res.writableEnded) {
         sendEvent(res, 'heartbeat', { timestamp: Date.now() });
       }
     }, 30000);
 
     // Cleanup on connection close
-    const cleanup = () => {
+    let cleanup = () => {
       if (debounceTimer) {
-        clearTimeout(debounceTimer);
+        timers.clearTimeout(debounceTimer);
         debounceTimer = null;
       }
-      clearInterval(heartbeatInterval);
-      if (watcher) {
-        watcher.close();
-        watcher = null;
-      }
-      if (filePollInterval) {
-        clearInterval(filePollInterval);
-        filePollInterval = null;
-      }
+      timers.clearInterval(heartbeatInterval);
+      cleanupReportWatcher();
     };
 
     req.on('close', cleanup);
diff --git a/tests/server/routers/assets.test.js b/tests/server/routers/assets.test.js
index 63da92d0..faf6e2a7 100644
--- a/tests/server/routers/assets.test.js
+++ b/tests/server/routers/assets.test.js
@@ -3,49 +3,10 @@ import { existsSync, mkdirSync, rmSync, writeFileSync } from 'node:fs';
 import { join } from 'node:path';
 import { afterEach, beforeEach, describe, it } from 'node:test';
 import { createAssetsRouter } from '../../../src/server/routers/assets.js';
-
-/**
- * Creates a mock HTTP request
- */
-function createMockRequest(method = 'GET') {
-  return { method };
-}
-
-/**
- * Creates a mock HTTP response with tracking
- */
-function createMockResponse() {
-  let headers = {};
-  let statusCode = null;
-  let body = null;
-
-  return {
-    get statusCode() {
-      return statusCode;
-    },
-    set statusCode(code) {
-      statusCode = code;
-    },
-    setHeader(name, value) {
-      headers[name] = value;
-    },
-    getHeader(name) {
-      return headers[name];
-    },
-    end(content) {
-      body = content;
-    },
-    get headers() {
-      return headers;
-    },
-    get body() {
-      return body;
-    },
-    getParsedBody() {
-      return body && typeof body === 'string' ? JSON.parse(body) : body;
-    },
-  };
-}
+import {
+  createMockRequest,
+  createMockResponse,
+} from '../../helpers/http-mocks.js';
 
 describe('server/routers/assets', () => {
   let testDir = join(process.cwd(), '.test-assets-router');
diff --git a/tests/server/routers/auth.test.js b/tests/server/routers/auth.test.js
index 013da59d..4f06ebae 100644
--- a/tests/server/routers/auth.test.js
+++ b/tests/server/routers/auth.test.js
@@ -1,60 +1,10 @@
 import assert from 'node:assert';
-import { EventEmitter } from 'node:events';
 import { describe, it } from 'node:test';
 import { createAuthRouter } from '../../../src/server/routers/auth.js';
-
-/**
- * Creates a mock HTTP request with body support
- */
-function createMockRequest(method = 'GET', body = null) {
-  let emitter = new EventEmitter();
-  emitter.method = method;
-
-  if (body !== null) {
-    process.nextTick(() => {
-      emitter.emit('data', JSON.stringify(body));
-      emitter.emit('end');
-    });
-  }
-
-  return emitter;
-}
-
-/**
- * Creates a mock HTTP response with tracking
- */
-function createMockResponse() {
-  let headers = {};
-  let statusCode = null;
-  let body = null;
-
-  return {
-    get statusCode() {
-      return statusCode;
-    },
-    set statusCode(code) {
-      statusCode = code;
-    },
-    setHeader(name, value) {
-      headers[name] = value;
-    },
-    getHeader(name) {
-      return headers[name];
-    },
-    end(content) {
-      body = content;
-    },
-    get headers() {
-      return headers;
-    },
-    get body() {
-      return body;
-    },
-    getParsedBody() {
-      return body ? JSON.parse(body) : null;
-    },
-  };
-}
+import {
+  createMockRequest,
+  createMockResponse,
+} from '../../helpers/http-mocks.js';
 
 /**
  * Creates a mock auth service
diff --git a/tests/server/routers/cloud-proxy.test.js b/tests/server/routers/cloud-proxy.test.js
index 497b7b09..e6a03b55 100644
--- a/tests/server/routers/cloud-proxy.test.js
+++ b/tests/server/routers/cloud-proxy.test.js
@@ -1,60 +1,10 @@
 import assert from 'node:assert';
-import { EventEmitter } from 'node:events';
 import { describe, it } from 'node:test';
 import { createCloudProxyRouter } from '../../../src/server/routers/cloud-proxy.js';
-
-/**
- * Creates a mock HTTP request with body support
- */
-function createMockRequest(method = 'GET', body = null) {
-  let emitter = new EventEmitter();
-  emitter.method = method;
-
-  if (body !== null) {
-    process.nextTick(() => {
-      emitter.emit('data', JSON.stringify(body));
-      emitter.emit('end');
-    });
-  }
-
-  return emitter;
-}
-
-/**
- * Creates a mock HTTP response with tracking
- */
-function createMockResponse() {
-  let headers = {};
-  let statusCode = null;
-  let body = null;
-
-  return {
-    get statusCode() {
-      return statusCode;
-    },
-    set statusCode(code) {
-      statusCode = code;
-    },
-    setHeader(name, value) {
-      headers[name] = value;
-    },
-    getHeader(name) {
-      return headers[name];
-    },
-    end(content) {
-      body = content;
-    },
-    get headers() {
-      return headers;
-    },
-    get body() {
-      return body;
-    },
-    getParsedBody() {
-      return body ? JSON.parse(body) : null;
-    },
-  };
-}
+import {
+  createMockRequest,
+  createMockResponse,
+} from '../../helpers/http-mocks.js';
 
 /**
  * Creates a mock URL object
diff --git a/tests/server/routers/config.test.js b/tests/server/routers/config.test.js
index fad17dd2..d7a75c26 100644
--- a/tests/server/routers/config.test.js
+++ b/tests/server/routers/config.test.js
@@ -1,60 +1,10 @@
 import assert from 'node:assert';
-import { EventEmitter } from 'node:events';
 import { describe, it } from 'node:test';
 import { createConfigRouter } from '../../../src/server/routers/config.js';
-
-/**
- * Creates a mock HTTP request with body support
- */
-function createMockRequest(method = 'GET', body = null) {
-  let emitter = new EventEmitter();
-  emitter.method = method;
-
-  if (body !== null) {
-    process.nextTick(() => {
-      emitter.emit('data', JSON.stringify(body));
-      emitter.emit('end');
-    });
-  }
-
-  return emitter;
-}
-
-/**
- * Creates a mock HTTP response with tracking
- */
-function createMockResponse() {
-  let headers = {};
-  let statusCode = null;
-  let body = null;
-
-  return {
-    get statusCode() {
-      return statusCode;
-    },
-    set statusCode(code) {
-      statusCode = code;
-    },
-    setHeader(name, value) {
-      headers[name] = value;
-    },
-    getHeader(name) {
-      return headers[name];
-    },
-    end(content) {
-      body = content;
-    },
-    get headers() {
-      return headers;
-    },
-    get body() {
-      return body;
-    },
-    getParsedBody() {
-      return body ? JSON.parse(body) : null;
-    },
-  };
-}
+import {
+  createMockRequest,
+  createMockResponse,
+} from '../../helpers/http-mocks.js';
 
 /**
  * Creates a mock config service
diff --git a/tests/server/routers/dashboard.test.js b/tests/server/routers/dashboard.test.js
index 591a009b..f059f501 100644
--- a/tests/server/routers/dashboard.test.js
+++ b/tests/server/routers/dashboard.test.js
@@ -3,49 +3,10 @@ import { existsSync, mkdirSync, rmSync, writeFileSync } from 'node:fs';
 import { join } from 'node:path';
 import { afterEach, beforeEach, describe, it } from 'node:test';
 import { createDashboardRouter } from '../../../src/server/routers/dashboard.js';
-
-/**
- * Creates a mock HTTP request
- */
-function createMockRequest(method = 'GET') {
-  return { method };
-}
-
-/**
- * Creates a mock HTTP response with tracking
- */
-function createMockResponse() {
-  let headers = {};
-  let statusCode = null;
-  let body = null;
-
-  return {
-    get statusCode() {
-      return statusCode;
-    },
-    set statusCode(code) {
-      statusCode = code;
-    },
-    setHeader(name, value) {
-      headers[name] = value;
-    },
-    getHeader(name) {
-      return headers[name];
-    },
-    end(content) {
-      body = content;
-    },
-    get headers() {
-      return headers;
-    },
-    get body() {
-      return body;
-    },
-    getParsedBody() {
-      return body && typeof body === 'string' ? JSON.parse(body) : body;
-    },
-  };
-}
+import {
+  createMockRequest,
+  createMockResponse,
+} from '../../helpers/http-mocks.js';
 
 describe('server/routers/dashboard', () => {
   let testDir = join(process.cwd(), '.test-dashboard-router');
diff --git a/tests/server/routers/events.test.js b/tests/server/routers/events.test.js
index 669d5d37..f8c279b3 100644
--- a/tests/server/routers/events.test.js
+++ b/tests/server/routers/events.test.js
@@ -62,6 +62,66 @@ function createMockResponse() {
   };
 }
 
+function createManualTimers() {
+  let timeouts = [];
+  let intervals = new Set();
+
+  return {
+    setTimeout(fn) {
+      let timeout = { fn };
+      timeouts.push(timeout);
+      return timeout;
+    },
+    clearTimeout(timeout) {
+      timeouts = timeouts.filter(candidate => candidate !== timeout);
+    },
+    setInterval() {
+      let interval = {};
+      intervals.add(interval);
+      return interval;
+    },
+    clearInterval(interval) {
+      intervals.delete(interval);
+    },
+    flushTimeouts() {
+      let pending = timeouts;
+      timeouts = [];
+      for (let timeout of pending) {
+        timeout.fn();
+      }
+    },
+  };
+}
+
+function createEventsHarness(workingDir) {
+  let timers = createManualTimers();
+  let triggerReportDataChanged = () => {
+    throw new Error('report data watcher was not registered');
+  };
+  let cleanupCalled = false;
+  let handler = createEventsRouter({
+    workingDir,
+    timers,
+    watchReportData({ onReportDataChanged }) {
+      triggerReportDataChanged = onReportDataChanged;
+      return () => {
+        cleanupCalled = true;
+      };
+    },
+  });
+
+  return {
+    handler,
+    timers,
+    triggerReportDataChanged() {
+      triggerReportDataChanged();
+    },
+    get cleanupCalled() {
+      return cleanupCalled;
+    },
+  };
+}
+
 describe('server/routers/events', () => {
   let testDir = join(process.cwd(), '.test-events-router');
   let originalCwd = process.cwd();
@@ -230,20 +290,19 @@ describe('server/routers/events', () => {
     });
 
     it('sends update when report-data.json changes', async () => {
-      let handler = createEventsRouter({ workingDir: testDir });
+      let harness = createEventsHarness(testDir);
       let req = createMockRequest('GET');
       let res = createMockResponse();
 
-      await handler(req, res, '/api/events');
+      await harness.handler(req, res, '/api/events');
 
-      // Write initial data - this triggers the file watcher
       writeFileSync(
         join(testDir, '.vizzly', 'report-data.json'),
         JSON.stringify({ comparisons: [{ id: 'updated' }] })
       );
 
-      // Wait for debounce (100ms) + buffer
-      await new Promise(resolve => setTimeout(resolve, 200));
+      harness.triggerReportDataChanged();
+      harness.timers.flushTimeouts();
 
       let output = res.getOutput();
       assert.ok(output.includes('event: reportData'));
@@ -254,33 +313,35 @@ describe('server/routers/events', () => {
     });
 
     it('debounces rapid file changes', async () => {
-      let handler = createEventsRouter({ workingDir: testDir });
+      let harness = createEventsHarness(testDir);
       let req = createMockRequest('GET');
       let res = createMockResponse();
 
-      await handler(req, res, '/api/events');
+      await harness.handler(req, res, '/api/events');
 
       // Rapid file changes
       writeFileSync(
         join(testDir, '.vizzly', 'report-data.json'),
         JSON.stringify({ version: 1 })
       );
+      harness.triggerReportDataChanged();
       writeFileSync(
         join(testDir, '.vizzly', 'report-data.json'),
         JSON.stringify({ version: 2 })
       );
+      harness.triggerReportDataChanged();
       writeFileSync(
         join(testDir, '.vizzly', 'report-data.json'),
         JSON.stringify({ version: 3 })
       );
+      harness.triggerReportDataChanged();
 
-      // Wait for debounce
-      await new Promise(resolve => setTimeout(resolve, 200));
+      harness.timers.flushTimeouts();
 
       let output = res.getOutput();
       // Should only have one event with the final version
       let eventCount = (output.match(/event: reportData/g) || []).length;
-      assert.ok(eventCount >= 1, 'Should have at least one event');
+      assert.strictEqual(eventCount, 1, 'Should send one debounced event');
       assert.ok(output.includes('"version":3'), 'Should contain final version');
 
       // Clean up
@@ -288,11 +349,11 @@ describe('server/routers/events', () => {
     });
 
     it('does not send to closed connections', async () => {
-      let handler = createEventsRouter({ workingDir: testDir });
+      let harness = createEventsHarness(testDir);
       let req = createMockRequest('GET');
       let res = createMockResponse();
 
-      await handler(req, res, '/api/events');
+      await harness.handler(req, res, '/api/events');
 
       // Mark connection as ended
       res.end();
@@ -303,11 +364,10 @@ describe('server/routers/events', () => {
         JSON.stringify({ test: true })
       );
 
-      await new Promise(resolve => setTimeout(resolve, 200));
+      harness.triggerReportDataChanged();
+      harness.timers.flushTimeouts();
 
-      // Should not have written after end()
-      // The initial chunks should be empty since no initial data
-      assert.ok(true, 'Should not crash when writing to closed connection');
+      assert.strictEqual(res.getOutput(), '');
 
       // Clean up
       req.emit('close');
@@ -341,11 +401,11 @@ describe('server/routers/events', () => {
         JSON.stringify(initialData)
       );
 
-      let handler = createEventsRouter({ workingDir: testDir });
+      let harness = createEventsHarness(testDir);
       let req = createMockRequest('GET');
       let res = createMockResponse();
 
-      await handler(req, res, '/api/events');
+      await harness.handler(req, res, '/api/events');
 
       // Add a new comparison
       let updatedData = {
@@ -360,7 +420,8 @@ describe('server/routers/events', () => {
         JSON.stringify(updatedData)
       );
 
-      await new Promise(resolve => setTimeout(resolve, 200));
+      harness.triggerReportDataChanged();
+      harness.timers.flushTimeouts();
 
       let output = res.getOutput();
       assert.ok(output.includes('event: comparisonUpdate'));
@@ -382,11 +443,11 @@ describe('server/routers/events', () => {
         JSON.stringify(initialData)
       );
 
-      let handler = createEventsRouter({ workingDir: testDir });
+      let harness = createEventsHarness(testDir);
       let req = createMockRequest('GET');
       let res = createMockResponse();
 
-      await handler(req, res, '/api/events');
+      await harness.handler(req, res, '/api/events');
 
       // Change the comparison's status
       let updatedData = {
@@ -400,7 +461,8 @@ describe('server/routers/events', () => {
         JSON.stringify(updatedData)
       );
 
-      await new Promise(resolve => setTimeout(resolve, 200));
+      harness.triggerReportDataChanged();
+      harness.timers.flushTimeouts();
 
       let output = res.getOutput();
       assert.ok(output.includes('event: comparisonUpdate'));
@@ -429,11 +491,11 @@ describe('server/routers/events', () => {
         JSON.stringify(initialData)
       );
 
-      let handler = createEventsRouter({ workingDir: testDir });
+      let harness = createEventsHarness(testDir);
       let req = createMockRequest('GET');
       let res = createMockResponse();
 
-      await handler(req, res, '/api/events');
+      await harness.handler(req, res, '/api/events');
 
       // Remove comparison b
       let updatedData = {
@@ -445,7 +507,8 @@ describe('server/routers/events', () => {
         JSON.stringify(updatedData)
       );
 
-      await new Promise(resolve => setTimeout(resolve, 200));
+      harness.triggerReportDataChanged();
+      harness.timers.flushTimeouts();
 
       let output = res.getOutput();
       assert.ok(output.includes('event: comparisonRemoved'));
@@ -466,11 +529,11 @@ describe('server/routers/events', () => {
         JSON.stringify(initialData)
       );
 
-      let handler = createEventsRouter({ workingDir: testDir });
+      let harness = createEventsHarness(testDir);
       let req = createMockRequest('GET');
       let res = createMockResponse();
 
-      await handler(req, res, '/api/events');
+      await harness.handler(req, res, '/api/events');
 
       // Change summary fields only, same comparisons
       let updatedData = {
@@ -484,7 +547,8 @@ describe('server/routers/events', () => {
         JSON.stringify(updatedData)
       );
 
-      await new Promise(resolve => setTimeout(resolve, 200));
+      harness.triggerReportDataChanged();
+      harness.timers.flushTimeouts();
 
       let output = res.getOutput();
       assert.ok(output.includes('event: summaryUpdate'));
@@ -508,11 +572,11 @@ describe('server/routers/events', () => {
         JSON.stringify(initialData)
       );
 
-      let handler = createEventsRouter({ workingDir: testDir });
+      let harness = createEventsHarness(testDir);
       let req = createMockRequest('GET');
       let res = createMockResponse();
 
-      await handler(req, res, '/api/events');
+      await harness.handler(req, res, '/api/events');
 
       let chunksAfterInitial = res.chunks.length;
 
@@ -522,7 +586,8 @@ describe('server/routers/events', () => {
         JSON.stringify(initialData)
       );
 
-      await new Promise(resolve => setTimeout(resolve, 200));
+      harness.triggerReportDataChanged();
+      harness.timers.flushTimeouts();
 
       // No new chunks should have been written
       assert.strictEqual(
@@ -535,11 +600,11 @@ describe('server/routers/events', () => {
     });
 
     it('ignores changes to other files in .vizzly directory', async () => {
-      let handler = createEventsRouter({ workingDir: testDir });
+      let harness = createEventsHarness(testDir);
       let req = createMockRequest('GET');
       let res = createMockResponse();
 
-      await handler(req, res, '/api/events');
+      await harness.handler(req, res, '/api/events');
 
       // Write to a different file
       writeFileSync(
@@ -547,7 +612,7 @@ describe('server/routers/events', () => {
         JSON.stringify({ ignored: true })
       );
 
-      await new Promise(resolve => setTimeout(resolve, 200));
+      harness.timers.flushTimeouts();
 
       // Should not have sent any events
       let output = res.getOutput();
diff --git a/tests/server/routers/health.test.js b/tests/server/routers/health.test.js
index 0b14ebf4..7634e91f 100644
--- a/tests/server/routers/health.test.js
+++ b/tests/server/routers/health.test.js
@@ -3,49 +3,10 @@ import { existsSync, mkdirSync, rmSync, writeFileSync } from 'node:fs';
 import { join } from 'node:path';
 import { afterEach, beforeEach, describe, it } from 'node:test';
 import { createHealthRouter } from '../../../src/server/routers/health.js';
-
-/**
- * Creates a mock HTTP request
- */
-function createMockRequest(method = 'GET') {
-  return { method };
-}
-
-/**
- * Creates a mock HTTP response with tracking
- */
-function createMockResponse() {
-  let headers = {};
-  let statusCode = null;
-  let body = null;
-
-  return {
-    get statusCode() {
-      return statusCode;
-    },
-    set statusCode(code) {
-      statusCode = code;
-    },
-    setHeader(name, value) {
-      headers[name] = value;
-    },
-    getHeader(name) {
-      return headers[name];
-    },
-    end(content) {
-      body = content;
-    },
-    get headers() {
-      return headers;
-    },
-    get body() {
-      return body;
-    },
-    getParsedBody() {
-      return body ? JSON.parse(body) : null;
-    },
-  };
-}
+import {
+  createMockRequest,
+  createMockResponse,
+} from '../../helpers/http-mocks.js';
 
 describe('server/routers/health', () => {
   let testDir = join(process.cwd(), '.test-health-router');