test(rum-core): fix some flaky tests (#1561)

Author: david-luna

packages/rum-core/test/common/xhr-patch.spec.js

@@ -190,6 +190,7 @@ describe('xhrPatch', function () {
     const req = new window.XMLHttpRequest()
     const getEvents = registerEventListener(req)
     req.open('GET', 'https://elastic.co/guide', true)
+    req.timeout = 1
     req.addEventListener('loadend', () => {
       expect(getEvents(done).map(e => e.event)).toEqual(['schedule', 'invoke'])
     })

packages/rum-core/test/performance-monitoring/performance-monitoring.spec.js

@@ -198,8 +198,13 @@ describe('PerformanceMonitoring', function () {
 
   it('should notify when a transaction has been filtered out', function () {
     spyOn(configService, 'dispatchEvent')
-    var tr = new Transaction('transaction-no-duration', 'transaction-type')
-    tr.end()
+    // NOTE: tests in SauceLabs fail because the duration becomes 1. Setting the start & end
+    // times will ensure `duration` is 0.
+    var now = Date.now()
+    var tr = new Transaction('transaction-no-duration', 'transaction-type', {
+      startTime: now
+    })
+    tr.end(now)
 
     var payload = performanceMonitoring.createTransactionPayload(tr)
     expect(payload).toBeUndefined()