Reset context between test functions (#3506)

Author: thymikee

packages/jest-jasmine2/src/jasmine-async.js

@@ -37,7 +37,7 @@ function promisifyLifeCycleFunction(originalFn, env) {
     // We make *all* functions async and run `done` right away if they
     // didn't return a promise.
     const asyncFn = function(done) {
-      const returnValue = fn.call(this);
+      const returnValue = fn.call({});
 
       if (isPromise(returnValue)) {
         returnValue.then(done, done.fail);
@@ -67,7 +67,7 @@ function promisifyIt(originalFn, env) {
     }
 
     const asyncFn = function(done) {
-      const returnValue = fn.call(this);
+      const returnValue = fn.call({});
 
       if (isPromise(returnValue)) {
         returnValue.then(done, done.fail);