diff --git a/package.json b/package.json
index 0e8fe6de227..7f23b513f8d 100644
--- a/package.json
+++ b/package.json
@@ -131,10 +131,10 @@
   ],
   "scripts": {
     "setup": "node ./setup/setup.js",
-    "test": "node --max-old-space-size=4096 --experimental-vm-modules --trace-deprecation node_modules/jest-cli/bin/jest",
+    "test": "node --expose-gc --max-old-space-size=4096 --experimental-vm-modules --trace-deprecation node_modules/jest-cli/bin/jest --logHeapUsage",
     "test:update-snapshots": "yarn jest -u",
-    "test:integration": "node --max-old-space-size=4096 --experimental-vm-modules --trace-deprecation node_modules/jest-cli/bin/jest --testMatch \"<rootDir>/test/*.test.js\"",
-    "test:basic": "node --max-old-space-size=4096 --experimental-vm-modules --trace-deprecation node_modules/jest-cli/bin/jest --testMatch \"<rootDir>/te{st/TestCasesNormal,st/StatsTestCases,st/ConfigTestCases}.test.js\"",
+    "test:integration": "node --expose-gc --max-old-space-size=4096 --experimental-vm-modules --trace-deprecation node_modules/jest-cli/bin/jest --logHeapUsage --testMatch \"<rootDir>/test/*.test.js\"",
+    "test:basic": "node --expose-gc --max-old-space-size=4096 --experimental-vm-modules --trace-deprecation node_modules/jest-cli/bin/jest --logHeapUsage --testMatch \"<rootDir>/te{st/TestCasesNormal,st/StatsTestCases,st/ConfigTestCases}.test.js\"",
     "test:unit": "node --max-old-space-size=4096 --experimental-vm-modules --trace-deprecation node_modules/jest-cli/bin/jest --testMatch \"<rootDir>/test/*.unittest.js\"",
     "travis:integration": "yarn cover:integration --ci $JEST",
     "travis:basic": "yarn cover:basic --ci $JEST",
@@ -165,9 +165,9 @@
     "benchmark": "node --max-old-space-size=4096 --experimental-vm-modules --trace-deprecation node_modules/jest-cli/bin/jest --testMatch \"<rootDir>/test/*.benchmark.js\" --runInBand",
     "cover": "yarn cover:all && yarn cover:report",
     "cover:clean": "rimraf .nyc_output coverage",
-    "cover:all": "node --max-old-space-size=4096 --experimental-vm-modules node_modules/jest-cli/bin/jest --coverage",
-    "cover:basic": "node --max-old-space-size=4096 --experimental-vm-modules node_modules/jest-cli/bin/jest --testMatch \"<rootDir>/te{st/TestCasesNormal,st/StatsTestCases,st/ConfigTestCases}.test.js\" --coverage",
-    "cover:integration": "node --max-old-space-size=4096 --experimental-vm-modules node_modules/jest-cli/bin/jest --testMatch \"<rootDir>/test/*.test.js\" --coverage",
+    "cover:all": "node --expose-gc --max-old-space-size=4096 --experimental-vm-modules node_modules/jest-cli/bin/jest --logHeapUsage --coverage",
+    "cover:basic": "node --expose-gc --max-old-space-size=4096 --experimental-vm-modules node_modules/jest-cli/bin/jest --logHeapUsage --testMatch \"<rootDir>/te{st/TestCasesNormal,st/StatsTestCases,st/ConfigTestCases}.test.js\" --coverage",
+    "cover:integration": "node --expose-gc --max-old-space-size=4096 --experimental-vm-modules node_modules/jest-cli/bin/jest --logHeapUsage --testMatch \"<rootDir>/test/*.test.js\" --coverage",
     "cover:unit": "node --max-old-space-size=4096 --experimental-vm-modules node_modules/jest-cli/bin/jest --testMatch \"<rootDir>/test/*.unittest.js\" --coverage",
     "cover:types": "node node_modules/tooling/type-coverage",
     "cover:merge": "nyc merge .nyc_output coverage/coverage-nyc.json && rimraf .nyc_output",
diff --git a/test/ConfigTestCases.template.js b/test/ConfigTestCases.template.js
index c93656ac83e..bdd8eca4d67 100644
--- a/test/ConfigTestCases.template.js
+++ b/test/ConfigTestCases.template.js
@@ -128,6 +128,12 @@ const describeCases = config => {
 							}
 							if (testConfig.timeout) setDefaultTimeout(testConfig.timeout);
 						});
+						afterAll(() => {
+							// cleanup
+							options = undefined;
+							optionsArr = undefined;
+							testConfig = undefined;
+						});
 						beforeAll(() => {
 							rimraf.sync(cacheDirectory);
 						});
@@ -306,6 +312,11 @@ const describeCases = config => {
 											esmMode,
 											parentModule
 										) => {
+											if (testConfig === undefined) {
+												throw new Error(
+													`_require(${module}) called after all tests have completed`
+												);
+											}
 											if (Array.isArray(module) || /^\.\.?\//.test(module)) {
 												let content;
 												let p;
diff --git a/test/TestCases.template.js b/test/TestCases.template.js
index 03d0d5718a3..cfe9ee9cd13 100644
--- a/test/TestCases.template.js
+++ b/test/TestCases.template.js
@@ -11,8 +11,6 @@ const deprecationTracking = require("./helpers/deprecationTracking");
 const captureStdio = require("./helpers/captureStdio");
 const asModule = require("./helpers/asModule");
 
-const webpack = require("..");
-
 const casesPath = path.join(__dirname, "cases");
 let categories = fs.readdirSync(casesPath);
 categories = categories.map(cat => {
@@ -79,7 +77,7 @@ const describeCases = config => {
 							const terserForTesting = new TerserPlugin({
 								parallel: false
 							});
-							const options = {
+							let options = {
 								context: casesPath,
 								entry: "./" + category.name + "/" + testName + "/",
 								target: config.target || "async-node",
@@ -191,6 +189,8 @@ const describeCases = config => {
 							};
 							const cleanups = [];
 							afterAll(() => {
+								options = undefined;
+								testConfig = undefined;
 								for (const fn of cleanups) fn();
 							});
 							beforeAll(done => {
@@ -206,6 +206,7 @@ const describeCases = config => {
 											"cache1"
 										);
 										const deprecationTracker = deprecationTracking.start();
+										const webpack = require("..");
 										webpack(options, err => {
 											deprecationTracker();
 											options.output.path = oldPath;
@@ -224,6 +225,7 @@ const describeCases = config => {
 											"cache2"
 										);
 										const deprecationTracker = deprecationTracking.start();
+										const webpack = require("..");
 										webpack(options, err => {
 											deprecationTracker();
 											options.output.path = oldPath;
@@ -237,6 +239,7 @@ const describeCases = config => {
 							it(
 								testName + " should compile",
 								done => {
+									const webpack = require("..");
 									const compiler = webpack(options);
 									const run = () => {
 										const deprecationTracker = deprecationTracking.start();
diff --git a/test/configCases/asset-emitted/normal/index.js b/test/configCases/asset-emitted/normal/index.js
index c5d0cd4199f..9e1b6b1cd1b 100644
--- a/test/configCases/asset-emitted/normal/index.js
+++ b/test/configCases/asset-emitted/normal/index.js
@@ -1,3 +1 @@
-import("./module");
-
-it("should run", () => {});
+it("should run", () => import("./module"));
diff --git a/test/configCases/async-commons-chunk/existing-name/index.js b/test/configCases/async-commons-chunk/existing-name/index.js
index b05f483e755..b953c1a09b4 100644
--- a/test/configCases/async-commons-chunk/existing-name/index.js
+++ b/test/configCases/async-commons-chunk/existing-name/index.js
@@ -1,11 +1,17 @@
 const chunkLoadingSpy = jest.spyOn(__webpack_require__, "e");
 
-it("should not have duplicate chunks in blocks", function(done) {
+it("should not have duplicate chunks in blocks", function (done) {
+	let i = 0;
+	const d = () => {
+		if (i++ >= 3) done();
+	};
+
 	// This split point should contain: a
 	require.ensure(
 		[],
-		function(require) {
+		function (require) {
 			expect(require("./a")).toBe("a");
+			d();
 		},
 		"a"
 	);
@@ -14,9 +20,10 @@ it("should not have duplicate chunks in blocks", function(done) {
 	// have it only contain b and make chunk a be an async dependency.
 	require.ensure(
 		[],
-		function(require) {
+		function (require) {
 			expect(require("./a")).toBe("a");
 			expect(require("./b")).toBe("b");
+			d();
 		},
 		"a+b"
 	);
@@ -25,10 +32,11 @@ it("should not have duplicate chunks in blocks", function(done) {
 	// have it only contain c and make chunks a and a+b be async dependencies.
 	require.ensure(
 		[],
-		function(require) {
+		function (require) {
 			expect(require("./a")).toBe("a");
 			expect(require("./b")).toBe("b");
 			expect(require("./c")).toBe("c");
+			d();
 		},
 		"a+b+c"
 	);
@@ -46,5 +54,5 @@ it("should not have duplicate chunks in blocks", function(done) {
 		["a+b" /* == b */],
 		["a+b+c" /* == c */]
 	]);
-	done();
+	d();
 });
diff --git a/test/configCases/chunk-index/order-multiple-entries/entry1.js b/test/configCases/chunk-index/order-multiple-entries/entry1.js
index 32a5fa8c867..ff832a0bcad 100644
--- a/test/configCases/chunk-index/order-multiple-entries/entry1.js
+++ b/test/configCases/chunk-index/order-multiple-entries/entry1.js
@@ -1,6 +1,4 @@
 import "./a";
-import(/* webpackChunkName: "async" */ "./async");
+it("should compile", () => import(/* webpackChunkName: "async" */ "./async"));
 import "./b";
 import "./c";
-
-it("should compile", () => {});
diff --git a/test/configCases/chunk-index/order-multiple-entries/entry2.js b/test/configCases/chunk-index/order-multiple-entries/entry2.js
index aa9ec2317ed..92f9311d3d5 100644
--- a/test/configCases/chunk-index/order-multiple-entries/entry2.js
+++ b/test/configCases/chunk-index/order-multiple-entries/entry2.js
@@ -1,6 +1,4 @@
 import "./c";
-import(/* webpackChunkName: "async" */ "./async");
+it("should compile", () => import(/* webpackChunkName: "async" */ "./async"));
 import "./b";
 import "./a";
-
-it("should compile", () => {});
diff --git a/test/configCases/entry/issue-12562/app.js b/test/configCases/entry/issue-12562/app.js
index 6d8bc6abb95..03392144212 100644
--- a/test/configCases/entry/issue-12562/app.js
+++ b/test/configCases/entry/issue-12562/app.js
@@ -1 +1 @@
-import("./test.js");
+it("should load", () => import("./test.js"));
diff --git a/test/configCases/parsing/requirejs/index.js b/test/configCases/parsing/requirejs/index.js
index b032e27d81e..6d38fad8e66 100644
--- a/test/configCases/parsing/requirejs/index.js
+++ b/test/configCases/parsing/requirejs/index.js
@@ -9,12 +9,12 @@ it("should ignore require.config", function() {
 it("should have a require.version", function() {
 	expect(require.version).toBeTypeOf("string");
 });
-it("should have a requirejs.onError function", function() {
+it("should have a requirejs.onError function", function(done) {
 	function f(){}
 	expect(requirejs.onError).toBeTypeOf("undefined"); // has no default handler
 	var org = requirejs.onError;
 	requirejs.onError = f;
 	expect(requirejs.onError).toBe(f);
 	requirejs.onError = org;
-	require(["./file.js"], function() {});
+	require(["./file.js"], function() { done() });
 });
diff --git a/test/configCases/source-map/module-names/index.js b/test/configCases/source-map/module-names/index.js
index 49134e0227e..9bce8ae0465 100644
--- a/test/configCases/source-map/module-names/index.js
+++ b/test/configCases/source-map/module-names/index.js
@@ -5,21 +5,27 @@ function getSourceMap(filename) {
 	return map;
 }
 
-it("should include test.js in SourceMap", function() {
+it("should include test.js in SourceMap", function () {
 	var allSources = new Set();
 	var map = getSourceMap("bundle0.js");
-	for(var source of map.sources) allSources.add(source);
+	for (var source of map.sources) allSources.add(source);
 	map = getSourceMap("chunk-a.js");
-	for(var source of map.sources) allSources.add(source);
+	for (var source of map.sources) allSources.add(source);
 	map = getSourceMap("chunk-b.js");
-	for(var source of map.sources) allSources.add(source);
+	for (var source of map.sources) allSources.add(source);
 	expect(allSources).toContain("module");
 	allSources.delete("module");
 	expect(allSources).toContain("fallback");
-	for(const source of allSources) {
+	for (const source of allSources) {
 		expect(source).toMatch(/^fallback\**$/);
 	}
 });
 
-require.ensure(["./test.js"], function(require) {}, "chunk-a");
-require.ensure(["./test.js", "./test.js?1"], function(require) {}, "chunk-b");
+if (Math.random() < 0) {
+	require.ensure(["./test.js"], function (require) {}, "chunk-a");
+	require.ensure(
+		["./test.js", "./test.js?1"],
+		function (require) {},
+		"chunk-b"
+	);
+}
diff --git a/test/configCases/split-chunks/chunk-filename-delimiter-default/index.js b/test/configCases/split-chunks/chunk-filename-delimiter-default/index.js
index 4bb3b122e5d..653a17d44d5 100644
--- a/test/configCases/split-chunks/chunk-filename-delimiter-default/index.js
+++ b/test/configCases/split-chunks/chunk-filename-delimiter-default/index.js
@@ -1,10 +1,10 @@
 it("should run", function () {
-	Promise.all([
-		import(/* webpackChunkName: "a" */ "./a"),
-		import(/* webpackChunkName: "b" */ "./b")
-	]);
-
 	const files = require("fs").readdirSync(__dirname);
 	expect(files).toContain("a.bundle.js");
 	expect(files).toContain("b-b_js-c441f481.bundle.js");
+
+	return Promise.all([
+		import(/* webpackChunkName: "a" */ "./a"),
+		import(/* webpackChunkName: "b" */ "./b")
+	]);
 });
diff --git a/test/configCases/split-chunks/chunk-filename-delimiter/index.js b/test/configCases/split-chunks/chunk-filename-delimiter/index.js
index 141e9df534f..524184c6340 100644
--- a/test/configCases/split-chunks/chunk-filename-delimiter/index.js
+++ b/test/configCases/split-chunks/chunk-filename-delimiter/index.js
@@ -1,10 +1,10 @@
 it("should run", function () {
-	Promise.all([
-		import(/* webpackChunkName: "a" */ "./a"),
-		import(/* webpackChunkName: "b" */ "./b")
-	]);
-
 	const files = require("fs").readdirSync(__dirname);
 	expect(files).toContain("a.bundle.js");
 	expect(files).toContain("b---b_js---c441f481.bundle.js");
+
+	return Promise.all([
+		import(/* webpackChunkName: "a" */ "./a"),
+		import(/* webpackChunkName: "b" */ "./b")
+	]);
 });
diff --git a/test/configCases/split-chunks/issue-11337/index.js b/test/configCases/split-chunks/issue-11337/index.js
index 9dfd14f1dc1..38fdc8a741c 100644
--- a/test/configCases/split-chunks/issue-11337/index.js
+++ b/test/configCases/split-chunks/issue-11337/index.js
@@ -1,4 +1,2 @@
-it("should compile and evaluate fine", () => {});
-
-import("./a");
-import("./b");
+it("should compile and evaluate fine", () =>
+	Promise.all([import("./a"), import("./b")]));
diff --git a/test/configCases/split-chunks/issue-11513/index.js b/test/configCases/split-chunks/issue-11513/index.js
index b74ae1b44c7..1988e1d16a1 100644
--- a/test/configCases/split-chunks/issue-11513/index.js
+++ b/test/configCases/split-chunks/issue-11513/index.js
@@ -1,4 +1,2 @@
-it("should handle mixed size types chunk in splitChunks", async () => {
-	import("./chunk1");
-	import("./chunk2");
-});
+it("should handle mixed size types chunk in splitChunks", () =>
+	Promise.all([import("./chunk1"), import("./chunk2")]));
diff --git a/test/configCases/split-chunks/runtime-chunk-async-node/webpack.config.js b/test/configCases/split-chunks/runtime-chunk-async-node/webpack.config.js
index 6f0323a1ba2..a023f1b45f2 100644
--- a/test/configCases/split-chunks/runtime-chunk-async-node/webpack.config.js
+++ b/test/configCases/split-chunks/runtime-chunk-async-node/webpack.config.js
@@ -9,7 +9,10 @@ module.exports = {
 	},
 	target: "async-node",
 	output: {
-		filename: "[name].js"
+		filename: "[name].js",
+		library: {
+			type: "commonjs-module"
+		}
 	},
 	optimization: {
 		chunkIds: "named",