Fixed failing Selenium test

When user is logged in, visual editor is the default editor. When user
is not logged in, source editor is the default editor. When the test
does not log in, everything works just fine.

Bug: T126463
Change-Id: I1f15000a275657c0a92172781f57c5d1db537dcc

tests/browser/features/math.feature

@@ -1,9 +1,8 @@
-@chrome @en.wikipedia.beta.wmflabs.org @firefox @login
+@chrome @en.wikipedia.beta.wmflabs.org @firefox
 Feature: Math
 
   Scenario: Display simple math
-    Given I am logged in
-      And I am creating a page with source editor
+    Given I am editing a random page with source editor
     When I type <math>3 + 2</math>
       And I click Preview
     Then the page should contain an img tag

tests/browser/features/step_definitions/math_steps.rb

@@ -1,9 +1,5 @@
-Given(/^I am creating a page with source editor$/) do
-  visit(DoesNotExistPage, using_params: { page_name: @random_string })
-end
-
-When(/^I click link Create$/) do
-  on(DoesNotExistPage).action_edit_element.when_present.click
+Given(/^I am editing a random page with source editor$/) do
+  visit EditPage
 end
 
 When(/^I click Preview$/) do

tests/browser/features/support/pages/does_not_exist_page.rb

@@ -1,5 +0,0 @@
-class DoesNotExistPage
-  include PageObject
-
-  page_url '<%=params[:page_name]%>?action=edit'
-end

tests/browser/features/support/pages/edit_page.rb

@@ -1,6 +1,8 @@
 class EditPage
   include PageObject
 
+  page_url 'Special:Random?action=edit'
+
   text_area(:article_text, id: 'wpTextbox1')
   img(:math_image, class: 'tex')
   button(:preview, id: 'wpPreview')