Fixing testBrowsingPostEntryWithButton flakiness.

ios/chrome/browser/web/forms_egtest.mm

Index: ios/chrome/browser/web/forms_egtest.mm
diff --git a/ios/chrome/browser/web/forms_egtest.mm b/ios/chrome/browser/web/forms_egtest.mm
index 2210492ffa19019a3b7cd16d853daf33248f394a..ca9cf191045448aeac457b45255d1e32a6155cab 100644
--- a/ios/chrome/browser/web/forms_egtest.mm
+++ b/ios/chrome/browser/web/forms_egtest.mm
@@ -24,6 +24,9 @@
 #include "ios/web/public/test/response_providers/data_response_provider.h"
 #include "ios/web/public/test/url_test_util.h"
 
+using chrome_test_util::OmniboxText;
+using chrome_test_util::WebViewContainingText;
+
 namespace {
 
 // URL for a generic website in the user navigation flow.
@@ -124,8 +127,6 @@ void GetResponseHeadersAndBody(
 
 }  // namespace
 
-using chrome_test_util::OmniboxText;
-
 // Tests submition of HTTP forms POST data including cases involving navigation.
 @interface FormsTestCase : ChromeTestCase
 @end
@@ -346,4 +347,25 @@ - (void)testRepostFormCancellingAfterRedirect {
   [self waitForExpectedResponse:"GET"];
 }
 
+// Tests that pressing the button on a POST-based form changes the page and that
+// the back button works as expected afterwards.
+- (void)testGoBackButtonAfterFormSubmission {
+  GURL formURL = TestResponseProvider::GetFormUrl();
+  GURL destinationURL = TestResponseProvider::GetPrintFormDataUrl();
+
+  [ChromeEarlGrey loadURL:formURL];
+  chrome_test_util::TapWebViewElementWithId(kSubmitButton);
+  [[EarlGrey selectElementWithMatcher:WebViewContainingText(kExpectedPostData)]

[gchatz, 2017/04/10 18:43:23]

Should this use [self waitForExpectedResponse]?

[liaoyuke, 2017/04/10 18:48:09]

I think we should remove this method (in a separate CL). 

WebViewContainingText is a matcher that waits, and it will be refactored to
[ChromeEarlGrey waitForWebViewContainingText] some time in the future, so
removing [self waitForExpectedResponse] will make things easier and cleaner.

[gchatz, 2017/04/10 20:46:10]

Ok sounds good

[Eugene But (OOO till 7-30), 2017/04/10 20:46:45]

Could you please file a bug and add a TODO for this. Unless you plan a follow up
CL.

+      assertWithMatcher:grey_notNil()];
+  [[EarlGrey selectElementWithMatcher:OmniboxText(destinationURL.GetContent())]
+      assertWithMatcher:grey_notNil()];
+
+  // Go back and verify the browser navigates to the original URL.
+  [self goBack];
+  [[EarlGrey selectElementWithMatcher:WebViewContainingText("Unicorn")]
+      assertWithMatcher:grey_notNil()];
+  [[EarlGrey selectElementWithMatcher:OmniboxText(formURL.GetContent())]
+      assertWithMatcher:grey_notNil()];
+}
+
 @end