diff --git a/core/test/computed/metrics/interactive-test.js b/core/test/computed/metrics/interactive-test.js
index 42defd1f70..43955365bc 100644
--- a/core/test/computed/metrics/interactive-test.js
+++ b/core/test/computed/metrics/interactive-test.js
@@ -7,17 +7,31 @@
 import assert from 'assert/strict';
 
 import {Interactive} from '../../../computed/metrics/interactive.js';
-import {getURLArtifactFromDevtoolsLog, readJson} from '../../test-utils.js';
-
-const trace = readJson('../../fixtures/traces/progressive-app-m60.json', import.meta);
-const devtoolsLog = readJson('../../fixtures/traces/progressive-app-m60.devtools.log.json', import.meta);
+import {getURLArtifactFromDevtoolsLog, loadTraceFixture} from '../../test-utils.js';
 
+const {trace, devtoolsLog} = loadTraceFixture('progressive-app-m60');
 const URL = getURLArtifactFromDevtoolsLog(devtoolsLog);
 
-function generateNetworkRecords(records, timeOrigin) {
+/**
+ * Simple wrapper to just coerce return type to LanternMetric.
+ * @param {LH.Artifacts.MetricComputationDataInput} data
+ * @param {LH.Artifacts.ComputedContext} context
+ * @return {Promise<LH.Artifacts.LanternMetric>}
+ */
+async function getResult(data, context) {
+  const result = await Interactive.request(data, context);
+  return /** @type {LH.Artifacts.LanternMetric} */ (result);
+}
+
+/**
+ * @param {Array<Partial<LH.Artifacts.NetworkRequest> & {start: number, end: number}>} partialRecords
+ * @param {number} timeOrigin
+ * @return {LH.Artifacts.NetworkRequest[]}
+ */
+function generateNetworkRecords(partialRecords, timeOrigin) {
   const timeOriginInMs = timeOrigin / 1000;
-  return records.map(item => {
-    return {
+  return partialRecords.map(item => {
+    const record = {
       protocol: 'http',
       failed: item.failed || false,
       statusCode: item.statusCode || 200,
@@ -26,16 +40,20 @@ function generateNetworkRecords(records, timeOrigin) {
       startTime: (item.start + timeOriginInMs) / 1000,
       endTime: item.end === -1 ? -1 : (item.end + timeOriginInMs) / 1000,
     };
+    return /** @type {LH.Artifacts.NetworkRequest} */ (record);
   });
 }
+
 describe('Metrics: TTI', () => {
+  /** @type {{gatherMode: LH.Result.GatherMode}} */
   const gatherContext = {gatherMode: 'navigation'};
 
   it('should compute a simulated value', async () => {
-    const settings = {throttlingMethod: 'simulate'};
+    const settings = /** @type {LH.Config.Settings} */ (
+      {throttlingMethod: 'simulate'}
+    );
     const context = {settings, computedCache: new Map()};
-    const result = await Interactive.request({trace, devtoolsLog, gatherContext, settings, URL},
-      context);
+    const result = await getResult({trace, devtoolsLog, gatherContext, settings, URL}, context);
 
     expect({
       timing: Math.round(result.timing),
@@ -49,9 +67,11 @@ describe('Metrics: TTI', () => {
   });
 
   it('should compute an observed value (desktop)', async () => {
-    const settings = {throttlingMethod: 'provided', formFactor: 'desktop'};
+    const settings = /** @type {LH.Config.Settings} */ (
+      {throttlingMethod: 'provided', formFactor: 'desktop'}
+    );
     const context = {settings, computedCache: new Map()};
-    const result = await Interactive.request({trace, devtoolsLog, gatherContext, settings},
+    const result = await getResult({trace, devtoolsLog, gatherContext, settings, URL},
       context);
 
     assert.equal(Math.round(result.timing), 1582);
@@ -59,9 +79,11 @@ describe('Metrics: TTI', () => {
   });
 
   it('should compute an observed value (mobile)', async () => {
-    const settings = {throttlingMethod: 'provided', formFactor: 'mobile'};
+    const settings = /** @type {LH.Config.Settings} */ (
+      {throttlingMethod: 'provided', formFactor: 'mobile'}
+    );
     const context = {settings, computedCache: new Map()};
-    const result = await Interactive.request({trace, devtoolsLog, gatherContext, settings},
+    const result = await getResult({trace, devtoolsLog, gatherContext, settings, URL},
       context);
 
     assert.equal(Math.round(result.timing), 1582);
@@ -73,12 +95,12 @@ describe('Metrics: TTI', () => {
       const timeOrigin = 220023532;
       const firstContentfulPaint = 2500 * 1000 + timeOrigin;
       const traceEnd = 10000 * 1000 + timeOrigin;
-      const processedTrace = {timestamps: {timeOrigin, firstContentfulPaint, traceEnd}};
-
-      const cpu = [];
+      const processedTrace = /** @type {LH.Artifacts.ProcessedNavigation} */ (
+        {timestamps: {timeOrigin, firstContentfulPaint, traceEnd}}
+      );
       const network = generateNetworkRecords([], timeOrigin);
 
-      const result = Interactive.findOverlappingQuietPeriods(cpu, network, processedTrace);
+      const result = Interactive.findOverlappingQuietPeriods([], network, processedTrace);
       assert.deepEqual(result.cpuQuietPeriod, {start: 0, end: traceEnd / 1000});
       assert.deepEqual(result.networkQuietPeriod, {start: 0, end: traceEnd / 1000});
     });
@@ -87,13 +109,13 @@ describe('Metrics: TTI', () => {
       const timeOrigin = 220023532;
       const firstContentfulPaint = 2500 * 1000 + timeOrigin;
       const traceEnd = 5000 * 1000 + timeOrigin;
-      const processedTrace = {timestamps: {timeOrigin, firstContentfulPaint, traceEnd}};
-
-      const cpu = [];
+      const processedTrace = /** @type {LH.Artifacts.ProcessedNavigation} */ (
+        {timestamps: {timeOrigin, firstContentfulPaint, traceEnd}}
+      );
       const network = generateNetworkRecords([], timeOrigin);
 
       assert.throws(() => {
-        Interactive.findOverlappingQuietPeriods(cpu, network, processedTrace);
+        Interactive.findOverlappingQuietPeriods([], network, processedTrace);
       }, /NO.*IDLE_PERIOD/);
     });
 
@@ -101,9 +123,10 @@ describe('Metrics: TTI', () => {
       const timeOrigin = 220023532;
       const firstContentfulPaint = 2500 * 1000 + timeOrigin;
       const traceEnd = 10000 * 1000 + timeOrigin;
-      const processedTrace = {timestamps: {timeOrigin, firstContentfulPaint, traceEnd}};
+      const processedTrace = /** @type {LH.Artifacts.ProcessedNavigation} */ (
+        {timestamps: {timeOrigin, firstContentfulPaint, traceEnd}}
+      );
 
-      const cpu = [];
       const network = generateNetworkRecords([
         {start: 1400, end: 1900},
         {start: 2000, end: 9000},
@@ -112,7 +135,7 @@ describe('Metrics: TTI', () => {
       ], timeOrigin);
 
       assert.throws(() => {
-        Interactive.findOverlappingQuietPeriods(cpu, network, processedTrace);
+        Interactive.findOverlappingQuietPeriods([], network, processedTrace);
       }, /NO.*NETWORK_IDLE_PERIOD/);
     });
 
@@ -120,7 +143,9 @@ describe('Metrics: TTI', () => {
       const timeOrigin = 220023532;
       const firstContentfulPaint = 2500 * 1000 + timeOrigin;
       const traceEnd = 10000 * 1000 + timeOrigin;
-      const processedTrace = {timestamps: {timeOrigin, firstContentfulPaint, traceEnd}};
+      const processedTrace = /** @type {LH.Artifacts.ProcessedNavigation} */ (
+        {timestamps: {timeOrigin, firstContentfulPaint, traceEnd}}
+      );
 
       const cpu = [
         {start: 3000, end: 8000},
@@ -138,9 +163,10 @@ describe('Metrics: TTI', () => {
       const timeOrigin = 220023532;
       const firstContentfulPaint = 2500 * 1000 + timeOrigin;
       const traceEnd = 10000 * 1000 + timeOrigin;
-      const processedTrace = {timestamps: {timeOrigin, firstContentfulPaint, traceEnd}};
+      const processedTrace = /** @type {LH.Artifacts.ProcessedNavigation} */ (
+        {timestamps: {timeOrigin, firstContentfulPaint, traceEnd}}
+      );
 
-      const cpu = [];
       let network = generateNetworkRecords([
         {start: 0, end: -1, finished: false},
         {start: 0, end: 11000, failed: true},
@@ -150,7 +176,7 @@ describe('Metrics: TTI', () => {
       // Triple the requests to ensure it's not just the 2-quiet kicking in
       network = network.concat(network).concat(network);
 
-      const result = Interactive.findOverlappingQuietPeriods(cpu, network, processedTrace);
+      const result = Interactive.findOverlappingQuietPeriods([], network, processedTrace);
       assert.deepEqual(result.cpuQuietPeriod, {start: 0, end: traceEnd / 1000});
       assert.deepEqual(result.networkQuietPeriod, {start: 0, end: traceEnd / 1000});
     });
@@ -159,7 +185,9 @@ describe('Metrics: TTI', () => {
       const timeOrigin = 220023532;
       const firstContentfulPaint = 10000 * 1000 + timeOrigin;
       const traceEnd = 45000 * 1000 + timeOrigin;
-      const processedTrace = {timestamps: {timeOrigin, firstContentfulPaint, traceEnd}};
+      const processedTrace = /** @type {LH.Artifacts.ProcessedNavigation} */ (
+        {timestamps: {timeOrigin, firstContentfulPaint, traceEnd}}
+      );
 
       const cpu = [
         // quiet period before FMP
diff --git a/core/test/test-utils.js b/core/test/test-utils.js
index 9416a3db03..059d0a3573 100644
--- a/core/test/test-utils.js
+++ b/core/test/test-utils.js
@@ -106,6 +106,18 @@ function loadSourceMapAndUsageFixture(name) {
   };
 }
 
+/**
+ * @param {string} name
+ * @return {{devtoolsLog: LH.DevtoolsLog, trace: LH.Trace}}
+ */
+function loadTraceFixture(name) {
+  const dir = `${LH_ROOT}/core/test/fixtures/traces`;
+  return {
+    devtoolsLog: JSON.parse(fs.readFileSync(`${dir}/${name}.devtools.log.json`, 'utf-8')),
+    trace: JSON.parse(fs.readFileSync(`${dir}/${name}.json`, 'utf-8')),
+  };
+}
+
 /**
  * @template {unknown[]} TParams
  * @template TReturn
@@ -337,6 +349,7 @@ export {
   createDecomposedPromise,
   flushAllTimersAndMicrotasks,
   makeMocksForGatherRunner,
+  loadTraceFixture,
   fnAny,
   mockCommands,
   createScript,
diff --git a/tsconfig.json b/tsconfig.json
index 1c7794a665..d3a94cd3cb 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -105,8 +105,9 @@
   ],
   "files": [
     // Opt-in to typechecking for some core tests and test-support files.
-    "core/test/audits/script-treemap-data-test.js",
     "cli/test/fixtures/static-server.js",
+    "core/test/audits/script-treemap-data-test.js",
+    "core/test/computed/metrics/interactive-test.js",
     "core/test/fixtures/config-plugins/lighthouse-plugin-simple/plugin-simple.js",
   ],
 }