Starting UI Testing with Xcode on my project, hit a road block.
There is a subclass of UITextField called RSCustomTextField which has some UI customizations. Which is added to RSSearchHeadView, that contains the text field and button.
So Im not able to query the textfield as app.textfields["Search field"] since its a custom class, it shows as app.otherElements["Search field"]
It crashes on searchField.typeText("abc") displaying error Neither element nor any descendant has keyboard focus.. 
Even after tap() on the element. Note, I also tried setting accessibility trait on the subclass and the textfield as UIAccessibilityTraitSearchField yet no difference.
func testSearchIcon() {
  let searchField = app.otherElements["Search field"]    
  searchField.tap()
  searchField.typeText("abc")
  app.keys["delete"].tap()
  XCTAssertFalse(searchDubizzleElement.hittable)
}
Printing debugDescription on app gives the following output:
Element subtree:
 →Application 0x7fc1b3f3aa00: {{0.0, 0.0}, {375.0, 667.0}}, label: 'myappname-masked'
    Window 0x7fc1b3f439b0: Main Window, {{0.0, 0.0}, {375.0, 667.0}}
      Other 0x7fc1b3f55c20: traits: 8589934592, {{0.0, 0.0}, {375.0, 667.0}}
        Other 0x7fc1b3f43440: traits: 8589934592, {{0.0, 0.0}, {375.0, 667.0}}
          Other 0x7fc1b3f31830: traits: 8589934592, {{0.0, 0.0}, {375.0, 667.0}}
            Other 0x7fc1b3f61ff0: traits: 8589934592, {{0.0, 0.0}, {375.0, 667.0}}
              Other 0x7fc1b3f52820: traits: 8589934592, {{0.0, 0.0}, {375.0, 64.0}}
                Other 0x7fc1b3f4e190: traits: 8589934592, {{0.0, 0.0}, {375.0, 64.0}}
                  Button 0x7fc1b3f3a250: traits: 8589934593, {{5.0, 20.0}, {44.0, 44.0}}, label: 'search icon right'
                  Other 0x7fc1b3f349b0: traits: 8589935616, {{15.0, 20.0}, {345.0, 39.0}}, label: 'Search field'
                  Image 0x7fc1b3f3b3b0: traits: 8589934596, {{139.0, 22.0}, {97.0, 30.0}}, identifier: 'logo'
                  Button 0x7fc1b3f537a0: traits: 8589934593, {{326.0, 20.0}, {44.0, 44.0}}, label: 'your account icon'
              CollectionView 0x7fc1b3f32450: traits: 35192962023424, {{0.0, 64.0}, {375.0, 603.0}}
                Cell 0x7fc1b3f1e230: traits: 8589934592, {{0.0, 64.0}, {375.0, 50.0}}
......
 
     
     
    