diff --git a/build-system/test-configs/dep-check-config.js b/build-system/test-configs/dep-check-config.js
index e2179426a9ce1..39607f8070388 100644
--- a/build-system/test-configs/dep-check-config.js
+++ b/build-system/test-configs/dep-check-config.js
@@ -120,7 +120,7 @@ exports.rules = [
     filesMatching: 'ads/**/*.js',
     mustNotDependOn: 'src/**/*.js',
     allowlist: [
-      'ads/**->src/utils/dom-fingerprint.js',
+      'ads/**->src/core/dom/fingerprint.js',
       'ads/**->src/core/constants/consent-state.js',
       'ads/**->src/core/error/index.js',
       'ads/**->src/core/types/array.js',
diff --git a/src/document-ready.js b/src/core/document-ready.js
similarity index 100%
rename from src/document-ready.js
rename to src/core/document-ready.js
diff --git a/src/utils/dom-fingerprint.js b/src/core/dom/fingerprint.js
similarity index 97%
rename from src/utils/dom-fingerprint.js
rename to src/core/dom/fingerprint.js
index f6d15761e2c1c..a3cd3efe5b378 100644
--- a/src/utils/dom-fingerprint.js
+++ b/src/core/dom/fingerprint.js
@@ -14,8 +14,8 @@
  * limitations under the License.
  */
 
-import {isElement} from '../core/types';
-import {stringHash32} from '../core/types/string';
+import {isElement} from '../types';
+import {stringHash32} from '../types/string';
 
 /**
  * Gets a string of concatenated element names and relative positions
diff --git a/src/get-html.js b/src/core/dom/get-html.js
similarity index 90%
rename from src/get-html.js
rename to src/core/dom/get-html.js
index 0f469ea59cfcb..84392f26437c5 100644
--- a/src/get-html.js
+++ b/src/core/dom/get-html.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {isElement} from './core/types';
+import {isElement, isString} from '../types';
 
 /** @type {!Array<string>} */
 const excludedTags = ['script', 'style'];
@@ -76,14 +76,12 @@ export function getHtml(win, selector, attrs) {
  */
 function appendToResult(node, attrs, result) {
   const stack = [node];
-  const allowedAttrs = attrs.filter((attr) => {
-    return allowedAttributes.includes(attr);
-  });
+  const allowedAttrs = attrs.filter((attr) => allowedAttributes.includes(attr));
 
   while (stack.length > 0) {
     node = stack.pop();
 
-    if (typeof node === 'string') {
+    if (isString(node)) {
       result.push(node);
     } else if (node.nodeType === Node.TEXT_NODE) {
       result.push(node.textContent);
@@ -99,7 +97,7 @@ function appendToResult(node, attrs, result) {
 }
 
 /**
- *
+ * Returns true for allowed AMP tags and non-AMP tags except <script>/<style>
  * @param {!Element} node
  * @return {boolean}
  */
@@ -114,7 +112,7 @@ function isApplicableNode(node) {
 }
 
 /**
- *
+ * Constructs an open-tag with the provided attributes.
  * @param {!Element} node
  * @param {!Array<string>} attrs
  * @param {Array<string>} result
@@ -122,7 +120,7 @@ function isApplicableNode(node) {
 function appendOpenTag(node, attrs, result) {
   result.push(`<${node.tagName.toLowerCase()}`);
 
-  attrs.forEach(function (attr) {
+  attrs.forEach((attr) => {
     if (node.hasAttribute(attr)) {
       result.push(` ${attr}="${node.getAttribute(attr)}"`);
     }
diff --git a/src/utils/date.js b/src/core/dom/parse-date-attributes.js
similarity index 85%
rename from src/utils/date.js
rename to src/core/dom/parse-date-attributes.js
index 75cf23f13b9dd..0a716e47a59ca 100644
--- a/src/utils/date.js
+++ b/src/core/dom/parse-date-attributes.js
@@ -14,10 +14,16 @@
  * limitations under the License.
  */
 
-import {devAssert, userAssert} from '../core/assert';
-import {parseDate} from '../core/types/date';
+import {TimestampDef, parseDate} from '../types/date';
+import {devAssert, userAssert} from '../assert';
 
-/** Map from attribute names to their parsers. */
+/** @typedef {function(string):!TimestampDef} */
+let DateParserDef;
+
+/**
+ * Map from attribute names to their parsers.
+ * @type {Object<string, !DateParserDef>}
+ */
 const dateAttrParsers = {
   'datetime': (datetime) =>
     userAssert(parseDate(datetime), 'Invalid date: %s', datetime),
@@ -31,7 +37,7 @@ const dateAttrParsers = {
 /**
  * @param {!Element} element
  * @param {!Array<string>} dateAttrs list of attribute names
- * @return {?number}
+ * @return {?TimestampDef}
  */
 export function parseDateAttrs(element, dateAttrs) {
   const epoch = userAssert(
@@ -50,12 +56,13 @@ export function parseDateAttrs(element, dateAttrs) {
  * that is truthy.
  * @param {!Element} element
  * @param {!Array<string>} dateAttrs list of attribute names
- * @return {?number}
+ * @return {?TimestampDef}
  */
 function parseEpoch(element, dateAttrs) {
   // Validate provided dateAttrs outside the loop so it will fail when an
   // invalid attr is provided, even if that attribute isn't present on the
   // element.
+  /** @type {!Array<!DateParserDef>} */
   const parsers = dateAttrs.map((attrName) =>
     devAssert(
       dateAttrParsers[attrName],
diff --git a/src/utils/detached-dom-stream.js b/src/core/dom/stream/detached.js
similarity index 97%
rename from src/utils/detached-dom-stream.js
rename to src/core/dom/stream/detached.js
index 71afdbb9d9c69..4960bd6c85433 100644
--- a/src/utils/detached-dom-stream.js
+++ b/src/core/dom/stream/detached.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {devAssert} from '../core/assert';
+import {devAssert} from '../../assert';
 
 export class DetachedDomStream {
   /**
diff --git a/src/core/dom/stream/index.js b/src/core/dom/stream/index.js
new file mode 100644
index 0000000000000..6c83a0b9a2d5f
--- /dev/null
+++ b/src/core/dom/stream/index.js
@@ -0,0 +1,19 @@
+/**
+ * Copyright 2021 The AMP HTML Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS-IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+export {DetachedDomStream} from './detached';
+export {streamResponseToWriter} from './response';
+// TODO(#32693): Migrate DomTransformStream into core to finish the trio
diff --git a/src/utils/stream-response.js b/src/core/dom/stream/response.js
similarity index 94%
rename from src/utils/stream-response.js
rename to src/core/dom/stream/response.js
index 7b5a4557e3930..7568ba662d3ed 100644
--- a/src/utils/stream-response.js
+++ b/src/core/dom/stream/response.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {Deferred} from '../core/data-structures/promise';
+import {Deferred} from '../../data-structures/promise';
 
 /**
  * Decodes readable stream from response and writes to given writeable stream.
@@ -23,7 +23,7 @@ import {Deferred} from '../core/data-structures/promise';
  * This function should be replaced with transform stream when well supported.
  * @param {!Window} win
  * @param {!Response} response
- * @param {!./detached-dom-stream.DetachedDomStream} writer
+ * @param {!./detached.DetachedDomStream} writer
  * @return {!Promise<boolean>} true if response has content, false if
  * the response is empty.
  */
diff --git a/src/utils/dom-based-weakref.js b/src/core/dom/weakref.js
similarity index 100%
rename from src/utils/dom-based-weakref.js
rename to src/core/dom/weakref.js
diff --git a/src/core/dom/web-components.extern.js b/src/core/dom/web-components.extern.js
new file mode 100644
index 0000000000000..c4d427439337e
--- /dev/null
+++ b/src/core/dom/web-components.extern.js
@@ -0,0 +1,24 @@
+/**
+ * Copyright 2021 The AMP HTML Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS-IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * @fileoverview Externs for values expected to be on elements when Shadow DOM
+ * is supported
+ * @externs
+ */
+
+Element.prototype.attachShadow;
+Element.prototype.createShadowRoot;
diff --git a/src/web-components.js b/src/core/dom/web-components.js
similarity index 85%
rename from src/web-components.js
rename to src/core/dom/web-components.js
index 6bc0a62b058f4..db9d8b2ffb857 100644
--- a/src/web-components.js
+++ b/src/core/dom/web-components.js
@@ -16,7 +16,6 @@
 
 /**
  * Possible versions of Shadow DOM spec
- * @const
  * @enum {string}
  */
 export const ShadowDomVersion = {
@@ -26,7 +25,7 @@ export const ShadowDomVersion = {
 };
 
 /**
- * @type {ShadowDomVersion|undefined}
+ * @type {!ShadowDomVersion|undefined}
  * @visibleForTesting
  */
 let shadowDomSupportedVersion;
@@ -38,7 +37,7 @@ let shadowDomSupportedVersion;
 let shadowCssSupported;
 
 /**
- * @param {ShadowDomVersion|undefined} val
+ * @param {!ShadowDomVersion|undefined} val
  * @visibleForTesting
  */
 export function setShadowDomSupportedVersionForTesting(val) {
@@ -88,14 +87,11 @@ function isNative(func) {
 
 /**
  * Returns the supported version of Shadow DOM spec.
- * @param {?typeof Element=} opt_elementClass optional for testing
- * @return {ShadowDomVersion}
+ * @return {!ShadowDomVersion}
  */
-export function getShadowDomSupportedVersion(opt_elementClass) {
+export function getShadowDomSupportedVersion() {
   if (shadowDomSupportedVersion === undefined) {
-    shadowDomSupportedVersion = getShadowDomVersion(
-      opt_elementClass || Element
-    );
+    shadowDomSupportedVersion = getShadowDomVersion(Element);
   }
   return shadowDomSupportedVersion;
 }
@@ -103,8 +99,8 @@ export function getShadowDomSupportedVersion(opt_elementClass) {
 /**
  * Returns shadow dom version.
  *
- * @param {?typeof Element=} element
- * @return {ShadowDomVersion}
+ * @param {!typeof Element} element
+ * @return {!ShadowDomVersion}
  */
 function getShadowDomVersion(element) {
   if (!!element.prototype.attachShadow) {
diff --git a/src/utils/id-generator.js b/src/core/math/id-generator.js
similarity index 100%
rename from src/utils/id-generator.js
rename to src/core/math/id-generator.js
diff --git a/src/utils/math.js b/src/core/math/index.js
similarity index 99%
rename from src/utils/math.js
rename to src/core/math/index.js
index e377dd71959d7..2e2d6497ba4f1 100644
--- a/src/utils/math.js
+++ b/src/core/math/index.js
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {devAssert} from '../core/assert';
+import {devAssert} from '../assert';
 
 /**
  * Maps a value in a first range to its equivalent in a second range
diff --git a/src/layout-rect.js b/src/core/math/layout-rect.js
similarity index 95%
rename from src/layout-rect.js
rename to src/core/math/layout-rect.js
index deadb7a81569d..ebc1fe4636ff4 100644
--- a/src/layout-rect.js
+++ b/src/core/math/layout-rect.js
@@ -14,6 +14,15 @@
  * limitations under the License.
  */
 
+/**
+ * TODO(rcebulko): Migrate the actual ViewportInterface into core or an extern.
+ * @typedef {{
+ *   getHeight: function(this:ViewportInterfaceDef):number,
+ *   getWidth: function(this:ViewportInterfaceDef):number,
+ * }}
+ */
+let ViewportInterfaceDef;
+
 /**
  * The structure that combines position and size for an element. The exact
  * interpretation of position and size depends on the use case.
@@ -166,7 +175,7 @@ export function rectIntersection(var_args) {
  * Returns the position of r2 relative to r1
  * @param {!LayoutRectDef} r1
  * @param {!LayoutRectDef} r2
- * @return {RelativePositions}
+ * @return {!RelativePositions}
  */
 export function layoutRectsRelativePos(r1, r2) {
   if (r1.top < r2.top) {
@@ -182,9 +191,9 @@ export function layoutRectsRelativePos(r1, r2) {
  * Determines if any portion of a layoutBox would be onscreen in the given
  * viewport, when scrolled to the specified position.
  * @param {!LayoutRectDef} layoutBox
- * @param {!./service/viewport/viewport-interface.ViewportInterface} viewport
+ * @param {!ViewportInterfaceDef} viewport
  * @param {number} scrollPos
- * @return {RelativePositions}
+ * @return {!RelativePositions}
  */
 export function layoutPositionRelativeToScrolledViewport(
   layoutBox,
diff --git a/src/core/types/index.js b/src/core/types/index.js
index 1b613c2d9b24e..7062d28c67daf 100644
--- a/src/core/types/index.js
+++ b/src/core/types/index.js
@@ -28,3 +28,14 @@ export {isObject} from './object';
 export function isElement(value) {
   return value?.nodeType == /* Node.ELEMENT_NODE */ 1;
 }
+
+/**
+ * Determines if value is of number type and finite.
+ * NaN and Infinity are not considered a finite number.
+ * String numbers are not considered numbers.
+ * @param {*} value
+ * @return {boolean}
+ */
+export function isFiniteNumber(value) {
+  return typeof value === 'number' && isFinite(value);
+}
diff --git a/src/core/window.extern.js b/src/core/window.extern.js
index 68a259c89c44d..f122a4a859342 100644
--- a/src/core/window.extern.js
+++ b/src/core/window.extern.js
@@ -19,8 +19,20 @@
  * @externs
  */
 
-/** @type {undefined} */
+/**
+ * Never exists; used as part of post-compilation checks to verify DCE.
+ * @type {undefined}
+ */
 window.__AMP_ASSERTION_CHECK;
 
-/** @type {undefined|function(this:Window,!Error,Element=)} */
+/**
+ * Global error reporting handler; only present in AMP pages
+ * @type {undefined|function(this:Window,!Error,Element=)}
+ */
 window.__AMP_REPORT_ERROR;
+
+/**
+ * Counter for the DomBaseWeakRef polyfill.
+ * @type {undefined|number}
+ */
+window.__AMP_WEAKREF_ID;
diff --git a/src/polyfills/shame.extern.js b/src/polyfills/shame.extern.js
index b5c0f21e1eaeb..63c08376c1889 100644
--- a/src/polyfills/shame.extern.js
+++ b/src/polyfills/shame.extern.js
@@ -33,27 +33,7 @@
 /** @type {function(!Window)} */
 let install$$module$src$polyfills$fetch;
 
-// These definitions live in non-core files but are consumed by
-// get-bounding-client-rect. They should be removed as dom.js and layout-rect.js
-// are moved to core.
-/**
- * The structure that combines position and size for an element. The exact
- * interpretation of position and size depends on the use case. Replicated from
- * layout-rect.js
- *
- * @typedef {{
- *   top: number,
- *   bottom: number,
- *   left: number,
- *   right: number,
- *   width: number,
- *   height: number,
- *   x: number,
- *   y: number
- * }}
- */
-let LayoutRectDef$$module$src$layout_rect;
-/** @type {function(number, number, number, number):LayoutRectDef$$module$src$layout_rect} */
-let layoutRectLtwh$$module$src$layout_rect;
+// This definition lives in non-core files but is consumed by
+// get-bounding-client-rect. Is should be removed once dom.js is moved to core.
 /** @type {function(!Element):boolean} */
 let isConnectedNode$$module$src$dom;
diff --git a/src/types.js b/src/types.js
index 327871e10bc5d..a8644d9d20473 100644
--- a/src/types.js
+++ b/src/types.js
@@ -14,17 +14,6 @@
  * limitations under the License.
  */
 
-/**
- * Determines if value is of number type and finite.
- * NaN and Infinity are not considered a finite number.
- * String numbers are not considered numbers.
- * @param {*} value
- * @return {boolean}
- */
-export function isFiniteNumber(value) {
-  return typeof value === 'number' && isFinite(value);
-}
-
 /**
  * Externs declare that access `defaultView` from `document` or
  * `ownerDocument` is of type `(Window|null)` but most of our parameter types
diff --git a/test/unit/utils/test-detached-dom-stream.js b/test/unit/core/dom/stream/test-detached.js
similarity index 94%
rename from test/unit/utils/test-detached-dom-stream.js
rename to test/unit/core/dom/stream/test-detached.js
index 8bd8021f66230..0abc036e479b3 100644
--- a/test/unit/utils/test-detached-dom-stream.js
+++ b/test/unit/core/dom/stream/test-detached.js
@@ -14,9 +14,9 @@
  * limitations under the License.
  */
 
-import {DetachedDomStream} from '../../../src/utils/detached-dom-stream';
+import {DetachedDomStream} from '../../../../../src/utils/detached-dom-stream';
 
-describes.fakeWin('DetachedDomStream', {amp: true}, (env) => {
+describes.fakeWin('DOM - stream - DetachedDomStream', {amp: true}, (env) => {
   let win;
   let chunkSpy;
   let endSpy;
diff --git a/test/unit/utils/test-stream-response.js b/test/unit/core/dom/stream/test-response.js
similarity index 96%
rename from test/unit/utils/test-stream-response.js
rename to test/unit/core/dom/stream/test-response.js
index dc1378e3bf65d..05a5933ebab70 100644
--- a/test/unit/utils/test-stream-response.js
+++ b/test/unit/core/dom/stream/test-response.js
@@ -14,8 +14,8 @@
  * limitations under the License.
  */
 
-import {macroTask} from '../../../testing/yield';
-import {streamResponseToWriter} from '../../../src/utils/stream-response';
+import {macroTask} from '../../../../../testing/yield';
+import {streamResponseToWriter} from '../../../../..src/utils/stream-response';
 
 const chunk1 = `
  <!doctype html>
@@ -33,7 +33,7 @@ const chunk2 = `
  </html>
 `;
 
-describes.fakeWin('streamResponseToWriter', {}, (env) => {
+describes.fakeWin('DOM - stream - streamResponseToWriter', {}, (env) => {
   let writeSpy;
   let closeSpy;
   let mockWriter;
diff --git a/test/unit/core/dom/test-css.js b/test/unit/core/dom/test-css.js
index 511cd1446a989..92d08b8d61079 100644
--- a/test/unit/core/dom/test-css.js
+++ b/test/unit/core/dom/test-css.js
@@ -19,7 +19,7 @@ import {
   prependSelectorsWith,
 } from '../../../../src/core/dom/css';
 
-describes.sandboxed('CSS', {}, () => {
+describes.sandboxed('DOM - CSS selectors', {}, () => {
   describe('escapeCssSelectorIdent', () => {
     it('should escape', () => {
       expect(escapeCssSelectorIdent('a b')).to.equal('a\\ b');
diff --git a/test/unit/utils/test-dom-fingerprint.js b/test/unit/core/dom/test-fingerprint.js
similarity index 94%
rename from test/unit/utils/test-dom-fingerprint.js
rename to test/unit/core/dom/test-fingerprint.js
index df41889442510..f4a135e08e6e8 100644
--- a/test/unit/utils/test-dom-fingerprint.js
+++ b/test/unit/core/dom/test-fingerprint.js
@@ -17,9 +17,9 @@
 import {
   DomFingerprint,
   domFingerprintPlain,
-} from '../../../src/utils/dom-fingerprint';
+} from '../../../../src/core/dom/fingerprint';
 
-describes.realWin('domFingerprint', {}, (env) => {
+describes.realWin('DOM - fingerprint', {}, (env) => {
   let body;
   let div1;
   let ampAd;
diff --git a/test/unit/test-get-html.js b/test/unit/core/dom/test-get-html.js
similarity index 95%
rename from test/unit/test-get-html.js
rename to test/unit/core/dom/test-get-html.js
index 8525a387c9d7b..0e58741593d76 100644
--- a/test/unit/test-get-html.js
+++ b/test/unit/core/dom/test-get-html.js
@@ -26,9 +26,9 @@ const template = `<div id="wrapper">
 </div>
 `;
 
-import {getHtml} from '../../src/get-html';
+import {getHtml} from '../../../../src/core/dom/get-html';
 
-describes.sandboxed('getHtml', {}, () => {
+describes.sandboxed('DOM - getHtml', {}, () => {
   let element;
 
   beforeEach(() => {
diff --git a/test/unit/utils/test-date.js b/test/unit/core/dom/test-parse-date-attributes.js
similarity index 96%
rename from test/unit/utils/test-date.js
rename to test/unit/core/dom/test-parse-date-attributes.js
index 88fc7477e2d9b..0d79dc2fdd51b 100644
--- a/test/unit/utils/test-date.js
+++ b/test/unit/core/dom/test-parse-date-attributes.js
@@ -14,9 +14,9 @@
  * limitations under the License.
  */
 
-import {parseDateAttrs as parseDateAttrsBase} from '../../../src/utils/date';
+import {parseDateAttrs as parseDateAttrsBase} from '../../../../src/core/dom/parse-date-attributes';
 
-describes.sandboxed('utils/date', {}, (env) => {
+describes.sandboxed('DOM - parse date attributes', {}, (env) => {
   describe('parseDateAttrs', () => {
     const DATE = new Date(1514793600000);
     const DATE_STRING = DATE.toISOString();
diff --git a/test/unit/utils/test-dom-based-weakref.js b/test/unit/core/dom/test-weakref.js
similarity index 93%
rename from test/unit/utils/test-dom-based-weakref.js
rename to test/unit/core/dom/test-weakref.js
index 0111ed6401435..f8ace1af1cdf3 100644
--- a/test/unit/utils/test-dom-based-weakref.js
+++ b/test/unit/core/dom/test-weakref.js
@@ -13,9 +13,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-import {DomBasedWeakRef} from '../../../src/utils/dom-based-weakref';
+import {DomBasedWeakRef} from '../../../../src/core/dom/weakref';
 
-describes.realWin('dom-based-weakref', {}, (env) => {
+describes.realWin('DOM - DOM-based weakref', {}, (env) => {
   let element;
   beforeEach(() => {
     element = document.createElement('div');
diff --git a/test/unit/test-web-components.js b/test/unit/core/dom/test-web-components.js
similarity index 95%
rename from test/unit/test-web-components.js
rename to test/unit/core/dom/test-web-components.js
index 6d369e41f00df..144e965d7aa3d 100644
--- a/test/unit/test-web-components.js
+++ b/test/unit/core/dom/test-web-components.js
@@ -19,9 +19,9 @@ import {
   getShadowDomSupportedVersion,
   isShadowDomSupported,
   setShadowDomSupportedVersionForTesting,
-} from '../../src/web-components';
+} from '../../../../src/core/dom/web-components';
 
-describes.sandboxed('web components', {}, () => {
+describes.sandboxed('DOM - web components', {}, () => {
   beforeEach(() => {
     setShadowDomSupportedVersionForTesting(undefined);
   });
diff --git a/test/unit/test-layout-rect.js b/test/unit/core/math/test-layout-rect.js
similarity index 57%
rename from test/unit/test-layout-rect.js
rename to test/unit/core/math/test-layout-rect.js
index e583edcd3978a..eba0c6f09d04f 100644
--- a/test/unit/test-layout-rect.js
+++ b/test/unit/core/math/test-layout-rect.js
@@ -16,7 +16,7 @@
 
 import * as lr from '../../src/layout-rect';
 
-describes.sandboxed('LayoutRect', {}, () => {
+describes.sandboxed('math - LayoutRect', {}, () => {
   it('layoutRectLtwh', () => {
     const rect = lr.layoutRectLtwh(1, 2, 3, 4);
     expect(rect.left).to.equal(1);
@@ -117,115 +117,115 @@ describes.sandboxed('LayoutRect', {}, () => {
     });
     expect(lr.rectIntersection(rect1, rect2, rect3, rect4)).to.be.null;
   });
-});
 
-describes.sandboxed('cloneLayoutMarginsChangeDef', {}, () => {
-  it('should clone margins change correctly into new object', () => {
-    const marginsChange = {
-      top: 1,
-      bottom: 5,
-      left: 4,
-    };
-    const marginsChangeClone = lr.cloneLayoutMarginsChangeDef(marginsChange);
-    expect(marginsChangeClone).to.not.equal(marginsChange);
-    expect(marginsChangeClone.top).to.equal(1);
-    expect(marginsChangeClone.bottom).to.equal(5);
-    expect(marginsChangeClone.left).to.equal(4);
-    expect(marginsChangeClone.right).to.be.undefined;
+  describe('cloneLayoutMarginsChangeDef', {}, () => {
+    it('should clone margins change correctly into new object', () => {
+      const marginsChange = {
+        top: 1,
+        bottom: 5,
+        left: 4,
+      };
+      const marginsChangeClone = lr.cloneLayoutMarginsChangeDef(marginsChange);
+      expect(marginsChangeClone).to.not.equal(marginsChange);
+      expect(marginsChangeClone.top).to.equal(1);
+      expect(marginsChangeClone.bottom).to.equal(5);
+      expect(marginsChangeClone.left).to.equal(4);
+      expect(marginsChangeClone.right).to.be.undefined;
+    });
   });
-});
 
-describes.sandboxed('layoutRectSizeEquals', {}, () => {
-  it('should detect changes', () => {
-    const from = lr.layoutRectLtwh(10, 20, 1, 1);
-    const to = lr.layoutRectLtwh(10, 20, 40, 50);
-    expect(lr.layoutRectSizeEquals(from, to)).to.be.false;
-  });
+  describe('layoutRectSizeEquals', {}, () => {
+    it('should detect changes', () => {
+      const from = lr.layoutRectLtwh(10, 20, 1, 1);
+      const to = lr.layoutRectLtwh(10, 20, 40, 50);
+      expect(lr.layoutRectSizeEquals(from, to)).to.be.false;
+    });
 
-  it('should detect no changes', () => {
-    const from = lr.layoutRectLtwh(10, 20, 1, 1);
-    const to = lr.layoutRectLtwh(10, 20, 1, 1);
-    expect(lr.layoutRectSizeEquals(from, to)).to.be.true;
+    it('should detect no changes', () => {
+      const from = lr.layoutRectLtwh(10, 20, 1, 1);
+      const to = lr.layoutRectLtwh(10, 20, 1, 1);
+      expect(lr.layoutRectSizeEquals(from, to)).to.be.true;
+    });
   });
-});
 
-describes.sandboxed('areMarginsChanged', {}, () => {
-  it('should find margins are not changed when values the same', () => {
-    const margins = {
-      top: 1,
-      right: 2,
-      bottom: 3,
-      left: 4,
-    };
-    const changes = {
-      top: 1,
-      right: 2,
-      bottom: 3,
-      left: 4,
-    };
-    expect(lr.areMarginsChanged(margins, changes)).to.be.false;
-  });
+  describe('areMarginsChanged', {}, () => {
+    it('should find margins are not changed when values the same', () => {
+      const margins = {
+        top: 1,
+        right: 2,
+        bottom: 3,
+        left: 4,
+      };
+      const changes = {
+        top: 1,
+        right: 2,
+        bottom: 3,
+        left: 4,
+      };
+      expect(lr.areMarginsChanged(margins, changes)).to.be.false;
+    });
 
-  it('should find margins are not changed when all changes undefined', () => {
-    const margins = {
-      top: 1,
-      right: 2,
-      bottom: 3,
-      left: 4,
-    };
-    const changes = {};
-    expect(lr.areMarginsChanged(margins, changes)).to.be.false;
-  });
+    it('should find margins are not changed when all changes undefined', () => {
+      const margins = {
+        top: 1,
+        right: 2,
+        bottom: 3,
+        left: 4,
+      };
+      const changes = {};
+      expect(lr.areMarginsChanged(margins, changes)).to.be.false;
+    });
 
-  it('should find margins to be changed when top different', () => {
-    const margins = {
-      top: 1,
-      right: 2,
-      bottom: 3,
-      left: 4,
-    };
-    const changes = {
-      top: 5,
-    };
-    expect(lr.areMarginsChanged(margins, changes)).to.be.true;
-  });
+    it('should find margins to be changed when top different', () => {
+      const margins = {
+        top: 1,
+        right: 2,
+        bottom: 3,
+        left: 4,
+      };
+      const changes = {
+        top: 5,
+      };
+      expect(lr.areMarginsChanged(margins, changes)).to.be.true;
+    });
 
-  it('should find margins to be changed when right different', () => {
-    const margins = {
-      top: 1,
-      right: 2,
-      bottom: 3,
-      left: 4,
-    };
-    const changes = {
-      right: 5,
-    };
-    expect(lr.areMarginsChanged(margins, changes)).to.be.true;
-  });
+    it('should find margins to be changed when right different', () => {
+      const margins = {
+        top: 1,
+        right: 2,
+        bottom: 3,
+        left: 4,
+      };
+      const changes = {
+        right: 5,
+      };
+      expect(lr.areMarginsChanged(margins, changes)).to.be.true;
+    });
 
-  it('should find margins to be changed when bottom different', () => {
-    const margins = {
-      top: 1,
-      right: 2,
-      bottom: 3,
-      left: 4,
-    };
-    const changes = {
-      bottom: 5,
-    };
-    expect(lr.areMarginsChanged(margins, changes)).to.be.true;
-  });
+    it('should find margins to be changed when bottom different', () => {
+      const margins = {
+        top: 1,
+        right: 2,
+        bottom: 3,
+        left: 4,
+      };
+      const changes = {
+        bottom: 5,
+      };
+      expect(lr.areMarginsChanged(margins, changes)).to.be.true;
+    });
 
-  it('should find margins to be changed when left different', () => {
-    const margins = {
-      top: 1,
-      right: 2,
-      bottom: 3,
-      left: 4,
-    };
-    const changes = {
-      left: 5,
-    };
-    expect(lr.areMarginsChanged(margins, changes)).to.be.true;
+    it('should find margins to be changed when left different', () => {
+      const margins = {
+        top: 1,
+        right: 2,
+        bottom: 3,
+        left: 4,
+      };
+      const changes = {
+        left: 5,
+      };
+      expect(lr.areMarginsChanged(margins, changes)).to.be.true;
+    });
   });
 });
diff --git a/test/unit/utils/test-math.js b/test/unit/core/math/test-math.js
similarity index 99%
rename from test/unit/utils/test-math.js
rename to test/unit/core/math/test-math.js
index a30b9931a84a3..89f886a00aa79 100644
--- a/test/unit/utils/test-math.js
+++ b/test/unit/core/math/test-math.js
@@ -22,9 +22,9 @@ import {
   mapRange,
   mod,
   sum,
-} from '../../../src/utils/math';
+} from '../../../../src/utils/math';
 
-describes.sandboxed('utils/math', {}, () => {
+describes.sandboxed('math', {}, () => {
   describe('mapRange', () => {
     it('should map a number to the current value', () => {
       expect(mapRange(5, 0, 10, 40, 80)).to.equal(60);
diff --git a/test/unit/test-document-ready.js b/test/unit/core/test-document-ready.js
similarity index 98%
rename from test/unit/test-document-ready.js
rename to test/unit/core/test-document-ready.js
index 301e6dd0b0398..2b3f0368aa225 100644
--- a/test/unit/test-document-ready.js
+++ b/test/unit/core/test-document-ready.js
@@ -14,13 +14,13 @@
  * limitations under the License.
  */
 
-import {Services} from '../../src/services';
+import {Services} from '../../../src/services';
 import {
   isDocumentReady,
   onDocumentReady,
   whenDocumentComplete,
   whenDocumentReady,
-} from '../../src/document-ready';
+} from '../../../src/document-ready';
 
 describes.sandboxed('documentReady', {}, (env) => {
   let testDoc;
diff --git a/test/unit/test-types.js b/test/unit/core/types/test-types.js
similarity index 50%
rename from test/unit/test-types.js
rename to test/unit/core/types/test-types.js
index 751b7124d4b40..8095e08f0e394 100644
--- a/test/unit/test-types.js
+++ b/test/unit/core/types/test-types.js
@@ -14,27 +14,27 @@
  * limitations under the License.
  */
 
-import * as types from '../../src/types';
+import {isFiniteNumber} from '../../../../src/core/types';
 
-describes.sandboxed('Types', {}, () => {
+describes.sandboxed('type helpers', {}, () => {
   describe('isFiniteNumber', () => {
     it('should yield false for non-numbers', () => {
-      expect(types.isFiniteNumber(null)).to.be.false;
-      expect(types.isFiniteNumber(undefined)).to.be.false;
-      expect(types.isFiniteNumber('')).to.be.false;
-      expect(types.isFiniteNumber('2')).to.be.false;
-      expect(types.isFiniteNumber([])).to.be.false;
-      expect(types.isFiniteNumber([2])).to.be.false;
-      expect(types.isFiniteNumber({})).to.be.false;
-      expect(types.isFiniteNumber({'a': 2})).to.be.false;
-      expect(types.isFiniteNumber(true)).to.be.false;
-      expect(types.isFiniteNumber(NaN)).to.be.false;
+      expect(isFiniteNumber(null)).to.be.false;
+      expect(isFiniteNumber(undefined)).to.be.false;
+      expect(isFiniteNumber('')).to.be.false;
+      expect(isFiniteNumber('2')).to.be.false;
+      expect(isFiniteNumber([])).to.be.false;
+      expect(isFiniteNumber([2])).to.be.false;
+      expect(isFiniteNumber({})).to.be.false;
+      expect(isFiniteNumber({'a': 2})).to.be.false;
+      expect(isFiniteNumber(true)).to.be.false;
+      expect(isFiniteNumber(NaN)).to.be.false;
     });
 
     it('should yield true for numbers', () => {
-      expect(types.isFiniteNumber(3)).to.be.true;
-      expect(types.isFiniteNumber(3.2)).to.be.true;
-      expect(types.isFiniteNumber(123e5)).to.be.true;
+      expect(isFiniteNumber(3)).to.be.true;
+      expect(isFiniteNumber(3.2)).to.be.true;
+      expect(isFiniteNumber(123e5)).to.be.true;
     });
   });
 });