title: swift in UI test(test the num of cells in UITable View)
body: <p>I am very new to UI test. I have an <code>UITableView</code> in my storyboard and it contains some cells. 
  Update:
  I want to assert that the num of cells in <code>UITableView</code> when the app launches will be more than 0. But I don't know how to code this part.Using <code>NSPredicate</code>? Or others?</p>
  
  <pre><code> func testCellsNum()
  {
          let app = XCUIApplication()
          let tableCell = app.tableRows.count
      //Then what should I do ?
          XCTAssertGreaterThan(tableCell, 0, "should greater than 0")//this line doesn't work
  
  
  }
  </code></pre>