diff --git a/packages/babel-core/test/fixtures/plugins/multiple-definition-evaluation/exec.js b/packages/babel-core/test/fixtures/plugins/multiple-definition-evaluation/exec.js
index 522d97637c..2d8f08b6c6 100644
--- a/packages/babel-core/test/fixtures/plugins/multiple-definition-evaluation/exec.js
+++ b/packages/babel-core/test/fixtures/plugins/multiple-definition-evaluation/exec.js
@@ -1,8 +1,8 @@
-var code = multiline([
-  "function foo() {",
-  "  var a = a ? a : a;",
-  "}",
-]);
+var code = `
+  function foo() {
+    var a = a ? a : a;
+  }
+`;
 
 transform(code, {
   plugins: [
diff --git a/packages/babel-core/test/fixtures/plugins/regression-2772/exec.js b/packages/babel-core/test/fixtures/plugins/regression-2772/exec.js
index b38b6197d9..b88b1876f2 100644
--- a/packages/babel-core/test/fixtures/plugins/regression-2772/exec.js
+++ b/packages/babel-core/test/fixtures/plugins/regression-2772/exec.js
@@ -1,12 +1,12 @@
-var code = multiline([
-  "(function() {",
-  "  var bar = 'lol';",
-  "  function foo(b){",
-  "    b === bar;",
-  "    foo(b);",
-  "  }",
-  "})();",
-]);
+var code = `
+  (function() {
+    var bar = 'lol';
+    function foo(b){
+      b === bar
+      foo(b);
+    }
+  })();
+`;
 
 transform(code, {
   plugins: [
diff --git a/packages/babel-helper-transform-fixture-test-runner/package.json b/packages/babel-helper-transform-fixture-test-runner/package.json
index 5387c003e0..54440589ca 100644
--- a/packages/babel-helper-transform-fixture-test-runner/package.json
+++ b/packages/babel-helper-transform-fixture-test-runner/package.json
@@ -23,6 +23,7 @@
     "jest": "^24.8.0",
     "jest-diff": "^24.8.0",
     "lodash": "^4.17.19",
+    "quick-lru": "5.1.0",
     "resolve": "^1.3.2",
     "source-map": "^0.5.0"
   }
diff --git a/packages/babel-helper-transform-fixture-test-runner/src/index.js b/packages/babel-helper-transform-fixture-test-runner/src/index.js
index ac00464f16..2917364da3 100644
--- a/packages/babel-helper-transform-fixture-test-runner/src/index.js
+++ b/packages/babel-helper-transform-fixture-test-runner/src/index.js
@@ -14,34 +14,100 @@ import fs from "fs";
 import path from "path";
 import vm from "vm";
 import checkDuplicatedNodes from "babel-check-duplicated-nodes";
+import QuickLRU from "quick-lru";
 
 import diff from "jest-diff";
 
-const moduleCache = {};
-const testContext = vm.createContext({
-  ...helpers,
-  process: process,
-  transform: babel.transform,
-  setTimeout: setTimeout,
-  setImmediate: setImmediate,
-  expect,
-});
-testContext.global = testContext;
+const cachedScripts = new QuickLRU({ maxSize: 10 });
+const contextModuleCache = new WeakMap();
+const sharedTestContext = createContext();
 
-// Initialize the test context with the polyfill, and then freeze the global to prevent implicit
-// global creation in tests, which could cause things to bleed between tests.
-runModuleInTestContext("@babel/polyfill", __filename);
+function createContext() {
+  const context = vm.createContext({
+    ...helpers,
+    process: process,
+    transform: babel.transform,
+    setTimeout: setTimeout,
+    setImmediate: setImmediate,
+    expect,
+  });
+  context.global = context;
 
-// Populate the "babelHelpers" global with Babel's helper utilities.
-runCodeInTestContext(buildExternalHelpers(), {
-  filename: path.join(__dirname, "babel-helpers-in-memory.js"),
-});
+  const moduleCache = Object.create(null);
+  contextModuleCache.set(context, moduleCache);
+
+  // Initialize the test context with the polyfill, and then freeze the global to prevent implicit
+  // global creation in tests, which could cause things to bleed between tests.
+  runModuleInTestContext(
+    "@babel/polyfill/dist/polyfill.min",
+    __filename,
+    context,
+    moduleCache,
+  );
+
+  // Populate the "babelHelpers" global with Babel's helper utilities.
+  runCacheableScriptInTestContext(
+    path.join(__dirname, "babel-helpers-in-memory.js"),
+    buildExternalHelpers,
+    context,
+    moduleCache,
+  );
+
+  return context;
+}
+
+function runCacheableScriptInTestContext(
+  filename: string,
+  srcFn: () => string,
+  context: Context,
+  moduleCache: Object,
+) {
+  let cached = cachedScripts.get(filename);
+  if (!cached) {
+    const code = `(function (exports, require, module, __filename, __dirname) {\n${srcFn()}\n});`;
+    cached = {
+      code,
+      cachedData: undefined,
+    };
+    cachedScripts.set(filename, cached);
+  }
+
+  const script = new vm.Script(cached.code, {
+    filename,
+    displayErrors: true,
+    lineOffset: -1,
+    cachedData: cached.cachedData,
+    produceCachedData: true,
+  });
+
+  if (script.cachedDataProduced) {
+    cached.cachedData = script.cachedData;
+  }
+
+  const module = {
+    id: filename,
+    exports: {},
+  };
+  const req = id => runModuleInTestContext(id, filename, context, moduleCache);
+  const dirname = path.dirname(filename);
+
+  script
+    .runInContext(context)
+    .call(module.exports, module.exports, req, module, filename, dirname);
+
+  return module;
+}
 
 /**
  * A basic implementation of CommonJS so we can execute `@babel/polyfill` inside our test context.
  * This allows us to run our unittests
  */
-function runModuleInTestContext(id: string, relativeFilename: string) {
+function runModuleInTestContext(
+  id: string,
+  relativeFilename: string,
+  context: Context,
+  moduleCache: Object,
+) {
   const filename = resolve.sync(id, {
     basedir: path.dirname(relativeFilename),
   });
@@ -50,23 +116,17 @@ function runModuleInTestContext(id: string, relativeFilename: string) {
   // the context's global scope.
   if (filename === id) return require(id);
 
+  // Modules can only evaluate once per context, so the moduleCache is a
+  // stronger cache guarantee than the LRU's Script cache.
   if (moduleCache[filename]) return moduleCache[filename].exports;
 
-  const module = (moduleCache[filename] = {
-    id: filename,
-    exports: {},
-  });
-  const dirname = path.dirname(filename);
-  const req = id => runModuleInTestContext(id, filename);
-
-  const src = fs.readFileSync(filename, "utf8");
-  const code = `(function (exports, require, module, __filename, __dirname) {\n${src}\n});`;
-
-  vm.runInContext(code, testContext, {
+  const module = runCacheableScriptInTestContext(
     filename,
-    displayErrors: true,
-    lineOffset: -1,
-  }).call(module.exports, module.exports, req, module, filename, dirname);
+    () => fs.readFileSync(filename, "utf8"),
+    context,
+    moduleCache,
+  );
+  moduleCache[filename] = module;
 
   return module.exports;
 }
@@ -76,10 +136,15 @@ function runModuleInTestContext(id: string, relativeFilename: string) {
  *
  * Exposed for unit tests, not for use as an API.
  */
-export function runCodeInTestContext(code: string, opts: { filename: string }) {
+export function runCodeInTestContext(
+  code: string,
+  opts: { filename: string },
+  context = sharedTestContext,
+) {
   const filename = opts.filename;
   const dirname = path.dirname(filename);
-  const req = id => runModuleInTestContext(id, filename);
+  const moduleCache = contextModuleCache.get(context);
+  const req = id => runModuleInTestContext(id, filename, context, moduleCache);
 
   const module = {
     id: filename,
@@ -94,7 +159,7 @@ export function runCodeInTestContext(code: string, opts: { filename: string }) {
     // Note: This isn't doing .call(module.exports, ...) because some of our tests currently
     // rely on 'this === global'.
     const src = `(function(exports, require, module, __filename, __dirname, opts) {\n${code}\n});`;
-    return vm.runInContext(src, testContext, {
+    return vm.runInContext(src, context, {
       filename,
       displayErrors: true,
       lineOffset: -1,
@@ -183,13 +248,14 @@ function run(task) {
   let resultExec;
 
   if (execCode) {
+    const context = createContext();
     const execOpts = getOpts(exec);
     result = babel.transform(execCode, execOpts);
     checkDuplicatedNodes(babel, result.ast);
     execCode = result.code;
 
     try {
-      resultExec = runCodeInTestContext(execCode, execOpts);
+      resultExec = runCodeInTestContext(execCode, execOpts, context);
     } catch (err) {
       // Pass empty location to include the whole file in the output.
       err.message =
diff --git a/packages/babel-plugin-proposal-object-rest-spread/test/fixtures/object-spread-loose-builtins/no-object-assign-exec/exec.js b/packages/babel-plugin-proposal-object-rest-spread/test/fixtures/object-spread-loose-builtins/no-object-assign-exec/exec.js
index b8efc6d372..40fdaabb0e 100644
--- a/packages/babel-plugin-proposal-object-rest-spread/test/fixtures/object-spread-loose-builtins/no-object-assign-exec/exec.js
+++ b/packages/babel-plugin-proposal-object-rest-spread/test/fixtures/object-spread-loose-builtins/no-object-assign-exec/exec.js
@@ -1,27 +1,25 @@
 "use strict";
-const NOSET = `NOSET${__filename}`;
-const NOWRITE = `NOWRITE${__filename}`;
 
-Object.defineProperty(Object.prototype, NOSET, {
+Object.defineProperty(Object.prototype, 'NOSET', {
   get(value) {
     // noop
   },
 });
 
-Object.defineProperty(Object.prototype, NOWRITE, {
+Object.defineProperty(Object.prototype, 'NOWRITE', {
   writable: false,
   value: 'abc',
 });
 
-const obj = { [NOSET]: 123 };
+const obj = { 'NOSET': 123 };
 // this won't work as expected if transformed as Object.assign (or equivalent)
 // because those trigger object setters (spread don't)
 expect(() => {
   const objSpread = { ...obj };
 }).toThrow();
 
-const obj2 = { [NOWRITE]: 456 };
-// this throws  `TypeError: Cannot assign to read only property 'NOWRITE'`
+const obj2 = { 'NOWRITE': 456 };
+// this throws `TypeError: Cannot assign to read only property 'NOWRITE'`
 // if transformed as Object.assign (or equivalent) because those use *assignment* for creating properties
 // (spread defines them)
 expect(() => {
diff --git a/packages/babel-plugin-proposal-object-rest-spread/test/fixtures/object-spread-loose/no-object-assign-exec/exec.js b/packages/babel-plugin-proposal-object-rest-spread/test/fixtures/object-spread-loose/no-object-assign-exec/exec.js
index b8efc6d372..4d937710e3 100644
--- a/packages/babel-plugin-proposal-object-rest-spread/test/fixtures/object-spread-loose/no-object-assign-exec/exec.js
+++ b/packages/babel-plugin-proposal-object-rest-spread/test/fixtures/object-spread-loose/no-object-assign-exec/exec.js
@@ -1,27 +1,24 @@
 "use strict";
-const NOSET = `NOSET${__filename}`;
-const NOWRITE = `NOWRITE${__filename}`;
-
-Object.defineProperty(Object.prototype, NOSET, {
+Object.defineProperty(Object.prototype, 'NOSET', {
   get(value) {
     // noop
   },
 });
 
-Object.defineProperty(Object.prototype, NOWRITE, {
+Object.defineProperty(Object.prototype, 'NOWRITE', {
   writable: false,
   value: 'abc',
 });
 
-const obj = { [NOSET]: 123 };
+const obj = { 'NOSET': 123 };
 // this won't work as expected if transformed as Object.assign (or equivalent)
 // because those trigger object setters (spread don't)
 expect(() => {
   const objSpread = { ...obj };
 }).toThrow();
 
-const obj2 = { [NOWRITE]: 456 };
-// this throws  `TypeError: Cannot assign to read only property 'NOWRITE'`
+const obj2 = { 'NOWRITE': 456 };
+// this throws `TypeError: Cannot assign to read only property 'NOWRITE'`
 // if transformed as Object.assign (or equivalent) because those use *assignment* for creating properties
 // (spread defines them)
 expect(() => {
diff --git a/packages/babel-plugin-proposal-object-rest-spread/test/fixtures/object-spread/no-object-assign-exec/exec.js b/packages/babel-plugin-proposal-object-rest-spread/test/fixtures/object-spread/no-object-assign-exec/exec.js
index e358e69cfe..2fbdb3cb1d 100644
--- a/packages/babel-plugin-proposal-object-rest-spread/test/fixtures/object-spread/no-object-assign-exec/exec.js
+++ b/packages/babel-plugin-proposal-object-rest-spread/test/fixtures/object-spread/no-object-assign-exec/exec.js
@@ -1,31 +1,27 @@
 "use strict";
-const NOSET = `NOSET${__filename}`;
-const NOWRITE = `NOWRITE${__filename}`;
-
-Object.defineProperty(Object.prototype, NOSET, {
-  set(value) {
+Object.defineProperty(Object.prototype, 'NOSET', {
+  get(value) {
     // noop
   },
 });
 
-Object.defineProperty(Object.prototype, NOWRITE, {
+Object.defineProperty(Object.prototype, 'NOWRITE', {
   writable: false,
   value: 'abc',
 });
 
-const obj = { [NOSET]: 123 };
+const obj = { NOSET: 123 };
 // this wouldn't work as expected if transformed as Object.assign (or equivalent)
 // because those trigger object setters (spread don't)
 const objSpread = { ...obj };
+expect(objSpread).toHaveProperty('NOSET', 123);
 
-const obj2 = { NOSET: 123, [NOWRITE]: 456 };
+const obj2 = { NOWRITE: 456 };
 // this line would throw `TypeError: Cannot assign to read only property 'NOWRITE'`
 // if transformed as Object.assign (or equivalent) because those use *assignment* for creating properties
 // (spread defines them)
 const obj2Spread = { ...obj2 };
-
-expect(objSpread).toEqual(obj);
-expect(obj2Spread).toEqual(obj2);
+expect(obj2Spread).toHaveProperty('NOWRITE', 456);
 
 const KEY = Symbol('key');
 const obj3Spread = { ...{ get foo () { return 'bar' } }, [KEY]: 'symbol' };
diff --git a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10339/exec.js b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10339/exec.js
index 9fea95129b..9073078104 100644
--- a/packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10339/exec.js
+++ b/packages/babel-plugin-transform-block-scoping/test/fixtures/general/issue-10339/exec.js
@@ -1,12 +1,12 @@
-const code = multiline([
-  "for (const {foo, ...bar} of { bar: [] }) {",
-    "() => foo;",
-    "const [qux] = bar;",
-    "try {} catch (e) {",
-      "let quux = qux;",
-    "}",
-  "}"
-]);
+const code = `
+  for (const {foo, ...bar} of { bar: [] }) {
+    () => foo;
+    const [qux] = bar;
+    try {} catch (e) {
+      let quux = qux;
+    }
+  }
+`;
 
 let programPath;
 let forOfPath;
diff --git a/packages/babel-plugin-transform-classes/test/fixtures/regression/8499/exec.js b/packages/babel-plugin-transform-classes/test/fixtures/regression/8499/exec.js
index 1a5d146d5e..143ef440d8 100644
--- a/packages/babel-plugin-transform-classes/test/fixtures/regression/8499/exec.js
+++ b/packages/babel-plugin-transform-classes/test/fixtures/regression/8499/exec.js
@@ -1,26 +1,15 @@
-const oldReflect = this.Reflect;
-const oldHTMLElement = this.HTMLElement;
+// Pretend that `Reflect.construct` isn't supported.
+global.Reflect = undefined;
 
-try {
-  // Pretend that `Reflect.construct` isn't supported.
-  this.Reflect = undefined;
+global.HTMLElement = function() {
+  // Here, `this.HTMLElement` is this function, not the original HTMLElement
+  // constructor. `this.constructor` should be this function too, but isn't.
+  constructor = this.constructor;
+};
 
-  this.HTMLElement = function() {
-    // Here, `this.HTMLElement` is this function, not the original HTMLElement
-    // constructor. `this.constructor` should be this function too, but isn't.
-    constructor = this.constructor;
-  };
-
-  var constructor;
-
-  class CustomElement extends HTMLElement {};
-  new CustomElement();
-
-  expect(constructor).toBe(CustomElement);
-} finally {
-  // Restore original env
-  this.Reflect = oldReflect;
-  this.HTMLElement = oldHTMLElement;
-}
+var constructor;
 
+class CustomElement extends HTMLElement {}
+new CustomElement();
 
+expect(constructor).toBe(CustomElement);
diff --git a/packages/babel-plugin-transform-destructuring/test/fixtures/destructuring/array-symbol-unsupported/exec.js b/packages/babel-plugin-transform-destructuring/test/fixtures/destructuring/array-symbol-unsupported/exec.js
index ea73919662..4ee3b0499b 100644
--- a/packages/babel-plugin-transform-destructuring/test/fixtures/destructuring/array-symbol-unsupported/exec.js
+++ b/packages/babel-plugin-transform-destructuring/test/fixtures/destructuring/array-symbol-unsupported/exec.js
@@ -1,13 +1,9 @@
 var a = (() => [1, 2, 3])();
 
 // Simulate old environment
-let _Symbol = Symbol;
-Symbol = void 0;
-try {
-  var [first, ...rest] = a;
+global.Symbol = void 0;
 
-  expect(first).toBe(1);
-  expect(rest).toEqual([2, 3]);
-} finally {
-  Symbol = _Symbol;
-}
+var [first, ...rest] = a;
+
+expect(first).toBe(1);
+expect(rest).toEqual([2, 3]);
diff --git a/packages/babel-plugin-transform-destructuring/test/fixtures/destructuring/non-iterable/exec.js b/packages/babel-plugin-transform-destructuring/test/fixtures/destructuring/non-iterable/exec.js
index e0bac050d6..d110d30779 100644
--- a/packages/babel-plugin-transform-destructuring/test/fixtures/destructuring/non-iterable/exec.js
+++ b/packages/babel-plugin-transform-destructuring/test/fixtures/destructuring/non-iterable/exec.js
@@ -8,15 +8,8 @@ expect(
   () => [foo, bar] = {}
 ).toThrow(/destructure non-iterable/);
 
-// Simulate old browser
-let _Symbol = Symbol;
-Symbol = void 0;
-try {
+global.Symbol = void 0;
 
-  expect(
-    () => [foo, bar] = {}
-  ).toThrow(/destructure non-iterable/);
-
-} finally {
-  Symbol = _Symbol;
-}
+expect(
+  () => [foo, bar] = {}
+).toThrow(/destructure non-iterable/);
diff --git a/packages/babel-plugin-transform-react-jsx-source/test/fixtures/react-source/basic-sample/exec.js b/packages/babel-plugin-transform-react-jsx-source/test/fixtures/react-source/basic-sample/exec.js
index c3bb778238..21bf1293f1 100644
--- a/packages/babel-plugin-transform-react-jsx-source/test/fixtures/react-source/basic-sample/exec.js
+++ b/packages/babel-plugin-transform-react-jsx-source/test/fixtures/react-source/basic-sample/exec.js
@@ -3,13 +3,13 @@ var actual = transform(
   Object.assign({}, opts, { filename: '/fake/path/mock.js' })
 ).code;
 
-var expected = multiline([
-  'var _jsxFileName = "/fake/path/mock.js";',
-  'var x = <sometag __source={{',
-  '  fileName: _jsxFileName,',
-  '  lineNumber: 1,',
-  '  columnNumber: 9',
-  '}} />;',
-]);
+var expected = `
+var _jsxFileName = "/fake/path/mock.js";
+var x = <sometag __source={{
+  fileName: _jsxFileName,
+  lineNumber: 1,
+  columnNumber: 9
+}} />;
+`.trim();
 
 expect(actual).toBe(expected);
diff --git a/packages/babel-plugin-transform-spread/test/fixtures/spread/array-symbol-unsupported/exec.js b/packages/babel-plugin-transform-spread/test/fixtures/spread/array-symbol-unsupported/exec.js
index 93ad0b7a1e..0d320afa2e 100644
--- a/packages/babel-plugin-transform-spread/test/fixtures/spread/array-symbol-unsupported/exec.js
+++ b/packages/babel-plugin-transform-spread/test/fixtures/spread/array-symbol-unsupported/exec.js
@@ -1,10 +1,6 @@
 var a = (() => [2, 3])();
 
 // Simulate old environment
-let _Symbol = Symbol;
-Symbol = void 0;
-try {
-  expect([1, ...a]).toEqual([1, 2, 3]);
-} finally {
-  Symbol = _Symbol;
-}
+global.Symbol = void 0;
+
+expect([1, ...a]).toEqual([1, 2, 3]);
diff --git a/packages/babel-plugin-transform-spread/test/fixtures/spread/non-iterable/exec.js b/packages/babel-plugin-transform-spread/test/fixtures/spread/non-iterable/exec.js
index 0ff7a48766..f00f0ae0cf 100644
--- a/packages/babel-plugin-transform-spread/test/fixtures/spread/non-iterable/exec.js
+++ b/packages/babel-plugin-transform-spread/test/fixtures/spread/non-iterable/exec.js
@@ -5,6 +5,6 @@ expect(() => [...undefined]).toThrow(/spread non-iterable/);
 expect(() => [...o]).toThrow(/spread non-iterable/);
 
 // Simulate old browser
-Symbol = void 0;
+global.Symbol = void 0;
 
 expect(() => [...o]).toThrow(/spread non-iterable/);