guard in tests against accidental IS_REACT_ACT_ENVIRONMENT

Author: phryneas

tests/setup-env.js

@@ -1 +1,15 @@
 import './polyfill.js'
+
+Object.defineProperty(global, 'IS_REACT_ACT_ENVIRONMENT', {
+  get() {
+    return false
+  },
+  set(value) {
+    if (!!value) {
+      throw new Error(
+        'Cannot set IS_REACT_ACT_ENVIRONMENT to true, this probably pulled in some RTL dependency?',
+      )
+    }
+  },
+  configurable: true,
+})