diff --git a/package.json b/package.json
index 98abbd163..3be626aa1 100644
--- a/package.json
+++ b/package.json
@@ -41,6 +41,7 @@
     "@types/jest": "^24.0.11",
     "@typescript-eslint/eslint-plugin": "^4.1.1",
     "@typescript-eslint/parser": "^4.1.1",
+    "cross-env": "^7.0.3",
     "eslint": "^7.14.0",
     "eslint-config-prettier": "^6.11.0",
     "eslint-plugin-import": "^2.22.0",
diff --git a/packages/compat/src/detect-babel-plugins.ts b/packages/compat/src/detect-babel-plugins.ts
index de78c4647..4e596811a 100644
--- a/packages/compat/src/detect-babel-plugins.ts
+++ b/packages/compat/src/detect-babel-plugins.ts
@@ -1,4 +1,5 @@
 import { PluginItem } from '@babel/core';
+import { join, sep } from 'path';
 
 export function isEmberAutoImportDynamic(item: PluginItem): boolean {
   let pluginPath: string;
@@ -9,7 +10,8 @@ export function isEmberAutoImportDynamic(item: PluginItem): boolean {
   } else {
     return false;
   }
-  return /(^|\/)ember-auto-import\//.test(pluginPath);
+
+  return pluginPath.includes(join(sep, 'ember-auto-import', sep));
 }
 
 export function isCompactReexports(item: PluginItem): boolean {
@@ -21,7 +23,8 @@ export function isCompactReexports(item: PluginItem): boolean {
   } else {
     return false;
   }
-  return /(^|\/)babel-plugin-compact-reexports\//.test(pluginPath);
+
+  return pluginPath.includes(join('babel-plugin-compact-reexports', sep));
 }
 
 export function isColocationPlugin(item: PluginItem): boolean {
@@ -33,5 +36,6 @@ export function isColocationPlugin(item: PluginItem): boolean {
   } else {
     return false;
   }
-  return /(^|\/)ember-cli-htmlbars\/lib\/colocated-babel-plugin/.test(pluginPath);
+
+  return pluginPath.includes(join('ember-cli-htmlbars', 'lib', 'colocated-babel-plugin', sep));
 }
diff --git a/packages/compat/src/v1-app.ts b/packages/compat/src/v1-app.ts
index 74005622d..2b815c96f 100644
--- a/packages/compat/src/v1-app.ts
+++ b/packages/compat/src/v1-app.ts
@@ -1,6 +1,6 @@
 import { Memoize } from 'typescript-memoize';
 import { sync as pkgUpSync } from 'pkg-up';
-import { join, dirname } from 'path';
+import { join, dirname, isAbsolute } from 'path';
 import Funnel from 'broccoli-funnel';
 import mergeTrees from 'broccoli-merge-trees';
 import { WatchedDir } from 'broccoli-source';
@@ -532,7 +532,7 @@ export default class V1App {
     }
     // non node assets are local paths. They need an explicit `/` or `.` at
     // the start.
-    if (asset.startsWith('/') || asset.startsWith('.')) {
+    if (asset.startsWith('.') || isAbsolute(asset)) {
       return asset;
     }
     return './' + asset;
diff --git a/packages/router/package.json b/packages/router/package.json
index a3166d9ec..d1baaebf9 100644
--- a/packages/router/package.json
+++ b/packages/router/package.json
@@ -25,7 +25,7 @@
     "test": "npm-run-all lint:* test:*",
     "test:all": "ember try:each",
     "test:ember": "ember test --test-port=0",
-    "test:classic": "CLASSIC=true ember test --test-port=0"
+    "test:classic": "cross-env CLASSIC=true ember test --test-port=0"
   },
   "dependencies": {
     "@embroider/macros": "0.39.1",
@@ -40,6 +40,7 @@
     "@types/ember__routing": "^3.16.9",
     "babel-eslint": "^10.1.0",
     "broccoli-asset-rev": "^3.0.0",
+    "cross-env": "^7.0.3",
     "ember-cli": "~3.10.1",
     "ember-cli-dependency-checker": "^3.1.0",
     "ember-cli-eslint": "^5.1.0",
diff --git a/packages/util/package.json b/packages/util/package.json
index 922f90856..b8a76624d 100644
--- a/packages/util/package.json
+++ b/packages/util/package.json
@@ -23,8 +23,8 @@
     "lint:js:fix": "eslint . --fix",
     "start": "ember serve",
     "test": "npm-run-all lint test:*",
-    "test:ember": "EMBROIDER_TEST_SETUP_FORCE=embroider EMBROIDER_TEST_SETUP_OPTIONS=optimized ember test --test-port=0",
-    "test:classic": "EMBROIDER_TEST_SETUP_FORCE=classic ember test --test-port=0",
+    "test:ember": "cross-env EMBROIDER_TEST_SETUP_FORCE=embroider EMBROIDER_TEST_SETUP_OPTIONS=optimized ember test --test-port=0",
+    "test:classic": "cross-env EMBROIDER_TEST_SETUP_FORCE=classic ember test --test-port=0",
     "test:ember-compatibility": "ember try:each"
   },
   "dependencies": {
@@ -46,6 +46,7 @@
     "@typescript-eslint/parser": "^4.1.1",
     "babel-eslint": "^10.1.0",
     "broccoli-asset-rev": "^3.0.0",
+    "cross-env": "^7.0.3",
     "ember-auto-import": "^1.10.1",
     "ember-cli": "~3.25.2",
     "ember-cli-dependency-checker": "^3.2.0",
diff --git a/packages/webpack/src/ember-webpack.ts b/packages/webpack/src/ember-webpack.ts
index 0d48bf491..2922896d3 100644
--- a/packages/webpack/src/ember-webpack.ts
+++ b/packages/webpack/src/ember-webpack.ts
@@ -141,6 +141,7 @@ const Webpack: Packager<Options> = class Webpack implements PackagerInstance {
         hints: false,
       },
       plugins: [
+        //@ts-ignore
         new MiniCssExtractPlugin({
           filename: `chunk.[chunkhash].css`,
           chunkFilename: `chunk.[chunkhash].css`,
diff --git a/test-packages/engines-host-app/fastboot-tests/util.js b/test-packages/engines-host-app/fastboot-tests/util.js
index 73e3ff924..254a132e3 100644
--- a/test-packages/engines-host-app/fastboot-tests/util.js
+++ b/test-packages/engines-host-app/fastboot-tests/util.js
@@ -22,9 +22,9 @@ module.exports = function setup(hooks) {
     return dom.window.document;
   }
 
-  hooks.before(async function(assert) {
+  hooks.before(async function (assert) {
     if (!process.env.REUSE_FASTBOOT_BUILD) {
-      execFileSync('node', ['./node_modules/.bin/ember', 'build']);
+      execFileSync('node', ['../../node_modules/ember-cli/bin/ember', 'build']);
       process.env.REUSE_FASTBOOT_BUILD = 'true';
     }
     fastboot = new FastBoot({
@@ -33,7 +33,7 @@ module.exports = function setup(hooks) {
     });
     this.visit = visit.bind(this, assert);
   });
-  hooks.beforeEach(function(assert) {
+  hooks.beforeEach(function (assert) {
     this.visit = visit.bind(this, assert);
   });
 };
diff --git a/test-packages/engines-host-app/package.json b/test-packages/engines-host-app/package.json
index b43fc663d..f0298198d 100644
--- a/test-packages/engines-host-app/package.json
+++ b/test-packages/engines-host-app/package.json
@@ -18,9 +18,9 @@
     "start": "ember serve",
     "test": "npm-run-all lint:* test:*",
     "test:ember": "ember test --test-port=0",
-    "test:ember-classic": "CLASSIC=true ember test --test-port=0",
+    "test:ember-classic": "cross-env CLASSIC=true ember test --test-port=0",
     "test:fastboot": "qunit fastboot-tests",
-    "test:fastboot-classic": "CLASSIC=true qunit fastboot-tests"
+    "test:fastboot-classic": "cross-env CLASSIC=true qunit fastboot-tests"
   },
   "devDependencies": {
     "@ember/jquery": "^0.6.0",
diff --git a/test-packages/fastboot-app/fastboot-tests/util.js b/test-packages/fastboot-app/fastboot-tests/util.js
index fa6a6e79d..0e430ee70 100644
--- a/test-packages/fastboot-app/fastboot-tests/util.js
+++ b/test-packages/fastboot-app/fastboot-tests/util.js
@@ -22,9 +22,9 @@ module.exports = function setup(hooks, buildArgs = []) {
     return dom.window.document;
   }
 
-  hooks.before(async function(assert) {
+  hooks.before(async function (assert) {
     if (!process.env.REUSE_FASTBOOT_BUILD) {
-      execFileSync('node', ['./node_modules/.bin/ember', 'build', ...buildArgs]);
+      execFileSync('node', ['../../node_modules/ember-cli/bin/ember', 'build', ...buildArgs]);
       process.env.REUSE_FASTBOOT_BUILD = 'true';
     }
     fastboot = new FastBoot({
@@ -33,7 +33,7 @@ module.exports = function setup(hooks, buildArgs = []) {
     });
     this.visit = visit.bind(this, assert);
   });
-  hooks.beforeEach(function(assert) {
+  hooks.beforeEach(function (assert) {
     this.visit = visit.bind(this, assert);
   });
 };
diff --git a/test-packages/fastboot-app/package.json b/test-packages/fastboot-app/package.json
index 414d48cc6..53c7863ee 100644
--- a/test-packages/fastboot-app/package.json
+++ b/test-packages/fastboot-app/package.json
@@ -18,11 +18,11 @@
     "start": "ember serve",
     "test": "npm-run-all lint:* test:*",
     "test:ember": "ember test --test-port=0",
-    "test:ember-classic": "CLASSIC=true ember test --test-port=0",
+    "test:ember-classic": "cross-env CLASSIC=true ember test --test-port=0",
     "test:ember-production": "ember test --test-port=0 --environment=production",
     "test:fastboot": "qunit fastboot-tests",
-    "test:fastboot-production": "FASTBOOT_APP_PROD=true qunit fastboot-tests",
-    "test:fastboot-classic": "CLASSIC=true FASTBOOT_APP_PROD=true qunit fastboot-tests"
+    "test:fastboot-production": "cross-env FASTBOOT_APP_PROD=true qunit fastboot-tests",
+    "test:fastboot-classic": "cross-env CLASSIC=true FASTBOOT_APP_PROD=true qunit fastboot-tests"
   },
   "devDependencies": {
     "@ember/optional-features": "^1.3.0",
diff --git a/test-packages/macro-sample-addon/package.json b/test-packages/macro-sample-addon/package.json
index 51d4bd10b..9cb910530 100644
--- a/test-packages/macro-sample-addon/package.json
+++ b/test-packages/macro-sample-addon/package.json
@@ -21,7 +21,7 @@
     "test": "npm-run-all lint:* test:*",
     "test:all": "ember try:each",
     "test:ember": "ember test --test-port=0",
-    "test:classic:": "CLASSIC=true ember test --test-port=0"
+    "test:classic:": "cross-env CLASSIC=true ember test --test-port=0"
   },
   "dependencies": {
     "@embroider/macros": "0.39.1",
diff --git a/test-packages/macro-tests/package.json b/test-packages/macro-tests/package.json
index fecc8ab04..c0aa06e4b 100644
--- a/test-packages/macro-tests/package.json
+++ b/test-packages/macro-tests/package.json
@@ -18,7 +18,7 @@
     "start": "ember serve",
     "test": "npm-run-all lint:* test:*",
     "test:ember": "ember test --test-port=0",
-    "test:ember-classic": "CLASSIC=true ember test --test-port=0"
+    "test:ember-classic": "cross-env CLASSIC=true ember test --test-port=0"
   },
   "devDependencies": {
     "@ember/jquery": "^0.6.0",
diff --git a/test-packages/static-app/package.json b/test-packages/static-app/package.json
index fdee4984e..82af92cab 100644
--- a/test-packages/static-app/package.json
+++ b/test-packages/static-app/package.json
@@ -18,9 +18,9 @@
     "start": "ember serve",
     "test": "npm-run-all lint:* test:*",
     "test:ember": "ember test --test-port=0",
-    "test:ember-classic": "CLASSIC=true ember test --test-port=0",
-    "test:custom-root": "CUSTOM_ROOT_URL=/custom/ ember test --test-port=0",
-    "test:custom-relative-root": "CUSTOM_ROOT_URL=custom-relative-root-url/ ember test --test-port=0"
+    "test:ember-classic": "cross-env CLASSIC=true ember test --test-port=0",
+    "test:custom-root": "cross-env CUSTOM_ROOT_URL=/custom/ ember test --test-port=0",
+    "test:custom-relative-root": "cross-env CUSTOM_ROOT_URL=custom-relative-root-url/ ember test --test-port=0"
   },
   "devDependencies": {
     "@ember/jquery": "^0.5.2",
diff --git a/yarn.lock b/yarn.lock
index 537f4ef64..9ff2c5825 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -6115,6 +6115,13 @@ create-hmac@^1.1.0, create-hmac@^1.1.4, create-hmac@^1.1.7:
     safe-buffer "^5.0.1"
     sha.js "^2.4.8"
 
+cross-env@^7.0.3:
+  version "7.0.3"
+  resolved "https://registry.yarnpkg.com/cross-env/-/cross-env-7.0.3.tgz#865264b29677dc015ba8418918965dd232fc54cf"
+  integrity sha512-+/HKd6EgcQCJGh2PSjZuUitQBQynKor4wrFbRg4DtAgS1aWO+gU52xpH7M9ScGgXSYmAVS9bIJ8EzuaGw0oNAw==
+  dependencies:
+    cross-spawn "^7.0.1"
+
 cross-spawn@^6.0.0, cross-spawn@^6.0.5:
   version "6.0.5"
   resolved "https://registry.yarnpkg.com/cross-spawn/-/cross-spawn-6.0.5.tgz#4a5ec7c64dfae22c3a14124dbacdee846d80cbc4"
@@ -6126,7 +6133,7 @@ cross-spawn@^6.0.0, cross-spawn@^6.0.5:
     shebang-command "^1.2.0"
     which "^1.2.9"
 
-cross-spawn@^7.0.0, cross-spawn@^7.0.2, cross-spawn@^7.0.3:
+cross-spawn@^7.0.0, cross-spawn@^7.0.1, cross-spawn@^7.0.2, cross-spawn@^7.0.3:
   version "7.0.3"
   resolved "https://registry.yarnpkg.com/cross-spawn/-/cross-spawn-7.0.3.tgz#f73a85b9d5d41d045551c177e2882d4ac85728a6"
   integrity sha512-iRDPJKUPVEND7dHPO8rkbOnPpyDygcDFtWjpeWNCgy8WP2rXcxXL8TskReQl6OrB2G7+UJrags1q15Fudc7G6w==