     
     // removeFirst(_:)
     copy = array
+    copy.removeFirst(0)
+    XCTAssertTrue(array == copy)
     copy.removeFirst(2)
     XCTAssertTrue(array != copy)
     

    XCTAssertTrue(array.isEmpty)
    XCTAssertEqual(nil, array.first)
    XCTAssertEqual(nil, array.last)
    XCTAssertEqual(0, array.startIndex)
    XCTAssertEqual(0, array.endIndex)
    XCTAssertEqual(nil, array.generate().next())
  }
  
  func testInitialisesFromSequence() {

    
    // removeLast(_:)
    copy = array
    copy.removeLast(0)
    XCTAssertTrue(array == copy)
    copy.removeLast(2)
    XCTAssertTrue(array != copy)
    
