Ensure that tests don't leave mutated global state in the environment.

packages/babel-node/test/index.js

@@ -177,6 +177,16 @@ fs.readdirSync(fixtureLoc).forEach(function(binName) {
 
   const suiteLoc = path.join(fixtureLoc, binName);
   describe("bin/" + binName, function() {
+    let cwd;
+
+    beforeEach(() => {
+      cwd = process.cwd();
+    });
+
+    afterEach(() => {
+      process.chdir(cwd);
+    });
+
     fs.readdirSync(suiteLoc).forEach(function(testName) {
       if (testName[0] === ".") return;
 

packages/babel-preset-env/test/debug-fixtures.js

@@ -76,6 +76,16 @@ const buildTest = opts => {
 };
 
 describe("debug output", () => {
+  let cwd;
+
+  beforeEach(() => {
+    cwd = process.cwd();
+  });
+
+  afterEach(() => {
+    process.chdir(cwd);
+  });
+
   fs.readdirSync(fixtureLoc).forEach(testName => {
     if (testName.slice(0, 1) === ".") return;
     const testLoc = path.join(fixtureLoc, testName);

packages/babel-preset-env/test/fixtures/preset-options/browserslist-config/options.json

@@ -1,7 +1,7 @@
 {
   "presets": [
     ["../../../../lib", {
-      "configPath": "../fixtures/preset-options/browserslist-config",
+      "configPath": "packages/babel-preset-env/test/fixtures/preset-options/browserslist-config",
       "modules": false
     }]
   ]

packages/babel-preset-env/test/fixtures/preset-options/browserslist-package/options.json

@@ -1,7 +1,7 @@
 {
   "presets": [
     ["../../../../lib", {
-      "configPath": "../fixtures/preset-options/browserslist-package",
+      "configPath": "packages/babel-preset-env/test/fixtures/preset-options/browserslist-package",
       "targets": {
         "chrome": 55
       },