diff --git a/flow-typed/node/assert.js b/flow-typed/node/assert.js
new file mode 100644
index 000000000..d72d22373
--- /dev/null
+++ b/flow-typed/node/assert.js
@@ -0,0 +1,55 @@
+// Missing flow types for node:assert
+declare module "assert" {
+  declare class AssertionError extends Error {}
+  declare type AssertStrict = {
+    (value: any, message?: string): void;
+    ok(value: any, message?: string): void;
+    fail(message?: string | Error): void;
+    // deprecated since v10.15
+    // fail(actual: any, expected: any, message: string, operator: string): void;
+    equal(actual: any, expected: any, message?: string): void;
+    notEqual(actual: any, expected: any, message?: string): void;
+    deepEqual(actual: any, expected: any, message?: string): void;
+    notDeepEqual(actual: any, expected: any, message?: string): void;
+    throws(
+      block: Function,
+      error?: Function | RegExp | (err: any) => boolean,
+      message?: string
+    ): void;
+    doesNotThrow(block: Function, message?: string): void;
+    ifError(value: any): void;
+    AssertionError: typeof AssertionError;
+    strict: AssertStrict;
+    ...
+  }
+  declare module.exports: {
+    (value: any, message?: string): void,
+    ok(value: any, message?: string): void,
+    fail(message?: string | Error): void,
+    // deprecated since v10.15
+    // fail(actual: any, expected: any, message: string, operator: string): void,
+    equal(actual: any, expected: any, message?: string): void,
+    notEqual(actual: any, expected: any, message?: string): void,
+    deepEqual(actual: any, expected: any, message?: string): void,
+    notDeepEqual(actual: any, expected: any, message?: string): void,
+    strictEqual(actual: any, expected: any, message?: string): void,
+    notStrictEqual(actual: any, expected: any, message?: string): void,
+    deepStrictEqual(actual: any, expected: any, message?: string): void,
+    notDeepStrictEqual(actual: any, expected: any, message?: string): void,
+    throws(
+      block: Function,
+      error?: Function | RegExp | (err: any) => boolean,
+      message?: string
+    ): void,
+    doesNotThrow(block: Function, message?: string): void,
+    rejects(
+      block: Function,
+      error?: Function | RegExp | (err: any) => boolean,
+      message?: string
+    ): void;
+    ifError(value: any): void,
+    AssertionError: typeof AssertionError,
+    strict: AssertStrict;
+    ...
+  }
+}
diff --git a/packages/core/integration-tests/test/bundler.js b/packages/core/integration-tests/test/bundler.js
index a234c6076..e6b8687eb 100644
--- a/packages/core/integration-tests/test/bundler.js
+++ b/packages/core/integration-tests/test/bundler.js
@@ -887,10 +887,10 @@ describe('bundler', function () {
     ]);
 
     let assetBar = findAsset(b, 'bar.js');
-    if (!assetBar) return assert(false);
+    if (!assetBar) return assert.fail();
 
     let assetC = findAsset(b, 'c.js');
-    if (!assetC) return assert(false);
+    if (!assetC) return assert.fail();
 
     assert(
       b
@@ -957,7 +957,7 @@ describe('bundler', function () {
       .find(
         (bundle) => !bundle.getMainEntry() && bundle.name.includes('runtime'),
       );
-    if (!aManifestBundle) return assert(false);
+    if (!aManifestBundle) return assert.fail();
 
     let bBundles = b
       .getBundles()
@@ -970,7 +970,7 @@ describe('bundler', function () {
         stop();
       }
     });
-    if (!aBundleManifestAsset) return assert(false);
+    if (!aBundleManifestAsset) return assert.fail();
 
     let aBundleManifestAssetCode = await aBundleManifestAsset.getCode();
 
@@ -1333,7 +1333,7 @@ describe('bundler', function () {
 
     // Asset should not be inlined
     const index = b.getBundles().find((b) => b.name.startsWith('index'));
-    if (!index) return assert(false);
+    if (!index) return assert.fail();
 
     const contents = overlayFS.readFileSync(index.filePath, 'utf8');
     assert(
diff --git a/packages/core/integration-tests/test/contentHashing.js b/packages/core/integration-tests/test/contentHashing.js
index b3bedd284..87e4cc67e 100644
--- a/packages/core/integration-tests/test/contentHashing.js
+++ b/packages/core/integration-tests/test/contentHashing.js
@@ -1,3 +1,4 @@
+// @flow
 import assert from 'assert';
 import path from 'path';
 import {
@@ -99,11 +100,19 @@ describe('content hashing', function () {
     async () => {
       let a = await _bundle(
         path.join(__dirname, 'integration/hash-distDir/a/index.html'),
-        {sourceMaps: true},
+        {
+          defaultTargetOptions: {
+            sourceMaps: true,
+          },
+        },
       );
       let b = await _bundle(
         path.join(__dirname, 'integration/hash-distDir/b/index.html'),
-        {sourceMaps: true},
+        {
+          defaultTargetOptions: {
+            sourceMaps: true,
+          },
+        },
       );
 
       let aBundles = a.getBundles();
@@ -113,7 +122,11 @@ describe('content hashing', function () {
       assert.equal(bBundles.length, 2);
 
       let aJS = aBundles.find((bundle) => bundle.type === 'js');
+      if (!aJS) return assert.fail();
+
       let bJS = bBundles.find((bundle) => bundle.type === 'js');
+      if (!bJS) return assert.fail();
+
       assert(/index\.[a-f0-9]*\.js/.test(path.basename(aJS.filePath)));
       assert.equal(aJS.name, bJS.name);
     },
diff --git a/packages/core/integration-tests/test/globals.js b/packages/core/integration-tests/test/globals.js
index 885efb0a2..f50904f2c 100644
--- a/packages/core/integration-tests/test/globals.js
+++ b/packages/core/integration-tests/test/globals.js
@@ -1,3 +1,4 @@
+// @flow
 import assert from 'assert';
 import path from 'path';
 
@@ -58,7 +59,6 @@ describe('globals', function () {
     it('when scope hoisting is disabled', async function () {
       let bundleGraph = await bundle(path.join(dir, 'index.js'), {
         defaultTargetOptions: {
-          context: 'browser',
           shouldScopeHoist: false,
         },
         inputFS: overlayFS,
@@ -84,7 +84,6 @@ describe('globals', function () {
     it.v2('when scope hoisting is enabled', async function () {
       let bundleGraph = await bundle(path.join(dir, 'index.js'), {
         defaultTargetOptions: {
-          context: 'browser',
           shouldScopeHoist: true,
         },
         inputFS: overlayFS,
diff --git a/packages/core/integration-tests/test/html.js b/packages/core/integration-tests/test/html.js
index 6a8ae7218..cf1373b1d 100644
--- a/packages/core/integration-tests/test/html.js
+++ b/packages/core/integration-tests/test/html.js
@@ -1,3 +1,4 @@
+// @flow
 import assert from 'assert';
 import {
   assertBundles,
@@ -94,6 +95,8 @@ describe('html', function () {
     assert(html.includes('https://unpkg.com/parcel-bundler'));
 
     let iconsBundle = b.getBundles().find((b) => b.name.startsWith('icons'));
+    if (!iconsBundle) return assert.fail();
+
     assert(
       html.includes('/' + path.basename(iconsBundle.filePath) + '#icon-code'),
     );
@@ -121,8 +124,8 @@ describe('html', function () {
       },
     ]);
 
-    assert(await outputFS.exists(path.join(distDir, 'a.html'), 'utf8'));
-    assert(await outputFS.exists(path.join(distDir, 'b.html'), 'utf8'));
+    assert(await outputFS.exists(path.join(distDir, 'a.html')));
+    assert(await outputFS.exists(path.join(distDir, 'b.html')));
   });
 
   it('should find href attr when not first', async function () {
@@ -462,7 +465,9 @@ describe('html', function () {
     let b = await bundle(
       path.join(__dirname, '/integration/html-css-js/index.html'),
       {
-        hmr: true,
+        // Test is skipped, hmr does not exist on InitialOptions
+        // Leaving it here to fix when the test is enabled in future
+        // hmr: true,
       },
     );
 
@@ -956,23 +961,25 @@ describe('html', function () {
       path.join(__dirname, '/integration/webmanifest/index.html'),
     );
 
-    assertBundles(b, {
-      name: 'index.html',
-      assets: ['index.html'],
-      childBundles: [
-        {
-          type: 'webmanifest',
-          assets: ['manifest.webmanifest'],
-          childBundles: [
-            {
-              type: 'txt',
-              assets: ['some.txt'],
-              childBundles: [],
-            },
-          ],
-        },
-      ],
-    });
+    assertBundles(b, [
+      {
+        name: 'index.html',
+        assets: ['index.html'],
+        childBundles: [
+          {
+            type: 'webmanifest',
+            assets: ['manifest.webmanifest'],
+            childBundles: [
+              {
+                type: 'txt',
+                assets: ['some.txt'],
+                childBundles: [],
+              },
+            ],
+          },
+        ],
+      },
+    ]);
   });
 
   it.skip("should treat webmanifest as an entry module so it doesn't get content hashed", async function () {
@@ -980,16 +987,18 @@ describe('html', function () {
       path.join(__dirname, '/integration/html-manifest/index.html'),
     );
 
-    assertBundles(b, {
-      name: 'index.html',
-      assets: ['index.html'],
-      childBundles: [
-        {
-          type: 'webmanifest',
-          assets: ['manifest.webmanifest'],
-        },
-      ],
-    });
+    assertBundles(b, [
+      {
+        name: 'index.html',
+        assets: ['index.html'],
+        childBundles: [
+          {
+            type: 'webmanifest',
+            assets: ['manifest.webmanifest'],
+          },
+        ],
+      },
+    ]);
 
     const html = await outputFS.readFile(
       path.join(__dirname, '/dist/index.html'),
@@ -1210,11 +1219,10 @@ describe('html', function () {
     ]);
 
     let bundles = b.getBundles();
+    let foundBundle = bundles.find((bundle) => bundle.type === 'html');
+    if (!foundBundle) return assert.fail();
 
-    let html = await outputFS.readFile(
-      bundles.find((bundle) => bundle.type === 'html').filePath,
-      'utf8',
-    );
+    let html = await outputFS.readFile(foundBundle.filePath, 'utf8');
 
     let urls = [...html.matchAll(/url\(([^)]*)\)/g)].map((m) => m[1]);
     assert.strictEqual(urls.length, 2);
@@ -1412,7 +1420,7 @@ describe('html', function () {
   for (let scopeHoist of [false, true]) {
     it.v2(
       'should expose top level declarations globally in inline <script> tags with dependencies with scopeHoist = ' +
-        scopeHoist,
+        scopeHoist.toString(),
       async function () {
         let b = await bundle(
           path.join(
@@ -1635,7 +1643,6 @@ describe('html', function () {
         path.join(__dirname, '/integration/html-inline-js-module/index.html'),
         {
           defaultTargetOptions: {
-            mode: 'production',
             shouldScopeHoist: true,
             engines: {
               browsers: '>= 0.25%',
@@ -1672,7 +1679,6 @@ describe('html', function () {
         path.join(__dirname, '/integration/html-js/index.html'),
         {
           defaultTargetOptions: {
-            mode: 'production',
             shouldScopeHoist: true,
             engines: {
               browsers: '>= 0.25%',
@@ -1697,26 +1703,27 @@ describe('html', function () {
       ]);
 
       let bundles = b.getBundles();
-      let html = await outputFS.readFile(
-        bundles.find((b) => b.type === 'html').filePath,
-        'utf8',
-      );
+      let foundBundleHtml = bundles.find((b) => b.type === 'html');
+      if (!foundBundleHtml) return assert.fail();
+
+      let html = await outputFS.readFile(foundBundleHtml.filePath, 'utf8');
       assert(html.includes('<script type="module" src='));
       assert(/<script src=".*?" nomodule/.test(html));
 
-      let js = await outputFS.readFile(
-        bundles.find(
-          (b) => b.type === 'js' && b.env.outputFormat === 'esmodule',
-        ).filePath,
-        'utf8',
+      let foundBundleJsEsm = bundles.find(
+        (b) => b.type === 'js' && b.env.outputFormat === 'esmodule',
       );
+      if (!foundBundleJsEsm) return assert.fail();
+
+      let js = await outputFS.readFile(foundBundleJsEsm.filePath, 'utf8');
       assert(/class \$[a-f0-9]+\$var\$Useless \{/.test(js));
 
-      js = await outputFS.readFile(
-        bundles.find((b) => b.type === 'js' && b.env.outputFormat === 'global')
-          .filePath,
-        'utf8',
+      let foundBundleJsGlobal = bundles.find(
+        (b) => b.type === 'js' && b.env.outputFormat === 'global',
       );
+      if (!foundBundleJsGlobal) return assert.fail();
+
+      js = await outputFS.readFile(foundBundleJsGlobal.filePath, 'utf8');
       assert(!/class \$[a-f0-9]+\$var\$Useless \{/.test(js));
     },
   );
@@ -1749,8 +1756,8 @@ describe('html', function () {
     let b = await bundle(
       path.join(__dirname, '/integration/html-js/index.html'),
       {
+        mode: 'production',
         defaultTargetOptions: {
-          mode: 'production',
           shouldScopeHoist: true,
           engines: {
             browsers: 'last 1 Chrome version',
@@ -1999,6 +2006,7 @@ describe('html', function () {
     let regex = /<script (?:type="[^"]+" )?src="([^"]*)"><\/script>/g;
     let match;
     while ((match = regex.exec(html)) !== null) {
+      if (!match) return assert.fail();
       insertedBundles.push(path.basename(match[1]));
     }
 
@@ -2061,6 +2069,7 @@ describe('html', function () {
     let regex = /<script (?:type="[^"]+" )?src="([^"]*)"><\/script>/g;
     let match;
     while ((match = regex.exec(html)) !== null) {
+      if (!match) return assert.fail();
       insertedBundles.push(path.basename(match[1]));
     }
 
@@ -2136,11 +2145,16 @@ describe('html', function () {
         let regex = /<script ([^>]*)><\/script>/g;
         let match;
         while ((match = regex.exec(html)) !== null) {
+          if (!match) return assert.fail();
           let attributes = new Map(
-            match[1].split(' ').map((a) => a.split('=')),
+            match[1]
+              .split(' ')
+              .map((a) => a.split('='))
+              .map(([a, ...b]) => [a, b.join('')]),
           );
-          let url = attributes.get('src').replace(/"/g, '');
-          assert(url);
+          let url = attributes.get('src')?.replace(/"/g, '');
+          if (!url) return assert.fail();
+
           if (attributes.get('type') === '"module"') {
             assert.strictEqual(attributes.size, 2);
             moduleScripts.push(path.basename(url));
@@ -2154,18 +2168,18 @@ describe('html', function () {
 
         for (let scripts of [moduleScripts, noModuleScripts]) {
           assert.strictEqual(scripts.length, 2);
-          assert(
-            b
-              .getBundles()
-              .find((b) => b.filePath.endsWith(scripts[0]))
-              .getMainEntry() == null,
-          );
-          assert(
-            b
-              .getBundles()
-              .find((b) => b.filePath.endsWith(scripts[1]))
-              .getMainEntry(),
-          );
+
+          let bundleA = b
+            .getBundles()
+            .find((b) => b.filePath.endsWith(scripts[0]));
+          if (!bundleA) return assert.fail();
+          assert(bundleA.getMainEntry() == null);
+
+          let bundleB = b
+            .getBundles()
+            .find((b) => b.filePath.endsWith(scripts[1]));
+          if (!bundleB) return assert.fail();
+          assert(bundleB.getMainEntry());
         }
       }
     },
@@ -2258,7 +2272,7 @@ describe('html', function () {
     });
 
     // could run in either order.
-    assert(output.sort(), ['a', 'b', 'c']);
+    assert.deepEqual(output.sort(), ['a', 'b', 'c']);
   });
 
   it.v2(
@@ -2317,7 +2331,7 @@ describe('html', function () {
       });
 
       // could run in either order.
-      assert(output.sort(), ['a', 'b', 'c']);
+      assert.deepEqual(output.sort(), ['a', 'b', 'c', 'c']);
     },
   );
 
@@ -2434,10 +2448,13 @@ describe('html', function () {
 
     let insertedBundles = [];
     let regex = /<script (?:type="[^"]+" )?src="([^"]*)"><\/script>/g;
-    let match;
-    while ((match = regex.exec(html)) !== null) {
+    let matches;
+    while ((matches = regex.exec(html)) !== null) {
+      if (!matches) continue;
+      let match = matches[1];
+      if (!match) continue;
       let bundle = bundles.find(
-        (b) => path.basename(b.filePath) === path.basename(match[1]),
+        (b) => path.basename(b.filePath) === path.basename(match),
       );
 
       insertedBundles.push(bundle);
@@ -2572,12 +2589,20 @@ describe('html', function () {
     ]);
 
     let htmlBundle = b.getBundles().find((b) => b.type === 'html');
+    if (!htmlBundle) return assert.fail();
+
     let htmlSiblings = b.getReferencedBundles(htmlBundle);
+    if (!htmlSiblings) return assert.fail();
+
     assert.equal(htmlSiblings.length, 2);
-    assert(htmlSiblings.some((b) => b.type === 'js'));
-    assert(htmlSiblings.some((b) => b.type === 'css'));
 
-    let worker = b.getChildBundles(htmlSiblings.find((b) => b.type === 'js'));
+    let jsSibling = htmlSiblings.find((b) => b.type === 'js');
+    if (!jsSibling) return assert.fail();
+
+    let cssSibling = htmlSiblings.find((b) => b.type === 'css');
+    if (!cssSibling) return assert.fail();
+
+    let worker = b.getChildBundles(jsSibling);
     assert.equal(worker.length, 1);
     let workerSiblings = b.getReferencedBundles(worker[0]);
     assert.equal(workerSiblings.length, 0);
@@ -2647,7 +2672,10 @@ describe('html', function () {
 
       for (let htmlBundle of b.getBundles().filter((b) => b.type === 'html')) {
         let htmlSiblings = b
-          .getReferencedBundles(htmlBundle, true)
+          .getReferencedBundles(htmlBundle, {
+            recursive: true,
+            includeInline: true,
+          })
           .map((b) => b.type)
           .sort();
         assert.deepEqual(htmlSiblings, ['css', 'js']);
@@ -2771,29 +2799,30 @@ describe('html', function () {
     );
 
     let bundles = b.getBundles();
-    let cssBundle = path.basename(
-      bundles.find((bundle) => bundle.filePath.endsWith('.css')).filePath,
-    );
-    let jsBundle = path.basename(
-      bundles.find((bundle) => bundle.filePath.endsWith('.js')).filePath,
-    );
+    let cssBundle = bundles.find((bundle) => bundle.filePath.endsWith('.css'));
+    if (!cssBundle) return assert.fail();
+    let cssBundleFileName = path.basename(cssBundle.filePath);
+
+    let jsBundle = bundles.find((bundle) => bundle.filePath.endsWith('.js'));
+    if (!jsBundle) return assert.fail();
+    let jsBundleFileName = path.basename(jsBundle.filePath);
 
     assert(
-      firstHtmlFile.includes(cssBundle),
-      `a.html should include a reference to ${cssBundle}`,
+      firstHtmlFile.includes(cssBundleFileName),
+      `a.html should include a reference to ${cssBundleFileName}`,
     );
     assert(
-      secondHtmlFile.includes(cssBundle),
-      `b.html should include a reference to ${cssBundle}`,
+      secondHtmlFile.includes(cssBundleFileName),
+      `b.html should include a reference to ${cssBundleFileName}`,
     );
 
     assert(
-      firstHtmlFile.includes(jsBundle),
-      `a.html should include a reference to ${jsBundle}`,
+      firstHtmlFile.includes(jsBundleFileName),
+      `a.html should include a reference to ${jsBundleFileName}`,
     );
     assert(
-      secondHtmlFile.includes(jsBundle),
-      `b.html should include a reference to ${jsBundle}`,
+      secondHtmlFile.includes(jsBundleFileName),
+      `b.html should include a reference to ${jsBundleFileName}`,
     );
   });
 
@@ -2888,10 +2917,10 @@ describe('html', function () {
       },
     );
 
-    let contents = await outputFS.readFile(
-      b.getBundles().find((b) => b.type === 'html').filePath,
-      'utf8',
-    );
+    let htmlBundle = b.getBundles().find((b) => b.type === 'html');
+    if (!htmlBundle) return assert.fail();
+    let contents = await outputFS.readFile(htmlBundle.filePath, 'utf8');
+
     assert.equal(
       contents.trim(),
       `<img src="data:image/svg+xml,%3Csvg%20width%3D%22120%22%20height%3D%22120%22%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%22%3E%0A%20%20%3Cfilter%20id%3D%22blur-_.%21~%2a%22%3E%0A%20%20%20%20%3CfeGaussianBlur%20stdDeviation%3D%225%22%3E%3C%2FfeGaussianBlur%3E%0A%20%20%3C%2Ffilter%3E%0A%20%20%3Ccircle%20cx%3D%2260%22%20cy%3D%2260%22%20r%3D%2250%22%20fill%3D%22green%22%20filter%3D%22url%28%27%23blur-_.%21~%2a%27%29%22%3E%3C%2Fcircle%3E%0A%3C%2Fsvg%3E%0A">`,
@@ -2985,6 +3014,7 @@ describe('html', function () {
         }
       });
     });
+    if (!youngerSibling) return assert.fail();
 
     assert(
       b.getReferencedBundles(youngerSibling).filter((b) => b == olderSibling)
diff --git a/packages/core/test-utils/src/utils.js b/packages/core/test-utils/src/utils.js
index 4aea6cd79..b707a2b6f 100644
--- a/packages/core/test-utils/src/utils.js
+++ b/packages/core/test-utils/src/utils.js
@@ -536,13 +536,16 @@ export function expectBundles(
   expect(bundleData).toEqual(expectedBundles);
 }
 
+export type AssertBundle = {|
+  name?: string | RegExp,
+  type?: string,
+  assets: Array<string>,
+  childBundles?: Array<AssertBundle>,
+|};
+
 export function assertBundles(
   bundleGraph: BundleGraph<PackagedBundle>,
-  expectedBundles: Array<{|
-    name?: string | RegExp,
-    type?: string,
-    assets: Array<string>,
-  |}>,
+  expectedBundles: Array<AssertBundle>,
 ) {
   let actualBundles = [];
   const byAlphabet = (a, b) => (a.toLowerCase() < b.toLowerCase() ? -1 : 1);