Update chai to 4.x (#6002)

packages/babel-helper-transform-fixture-test-runner/package.json

@@ -12,7 +12,7 @@
     "babel-core": "7.0.0-alpha.15",
     "babel-helper-fixtures": "7.0.0-alpha.15",
     "babel-polyfill": "7.0.0-alpha.15",
-    "chai": "^3.0.0",
+    "chai": "^4.1.0",
     "lodash": "^4.2.0",
     "resolve": "^1.3.2",
     "source-map": "^0.5.0"

packages/babel-helper-transform-fixture-test-runner/src/index.js

@@ -18,7 +18,6 @@ import vm from "vm";
 const moduleCache = {};
 const testContext = vm.createContext({
   ...helpers,
-  assert: chai.assert,
   process: process,
   transform: babel.transform,
   setTimeout: setTimeout,
@@ -26,6 +25,17 @@ const testContext = vm.createContext({
 });
 testContext.global = testContext;
 
+// Add chai's assert to the global context
+// It has to be required inside the testContext as otherwise some assertions do not
+// work as chai would reference globals (RegExp, Array, ...) from this context
+vm.runInContext(
+  "(function(require) { global.assert=require('chai').assert; });",
+  testContext,
+  {
+    displayErrors: true,
+  },
+)(id => runModuleInTestContext(id, __filename));
+
 // 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);