components/FlexibleHeader/tests/unit/FlexibleHeaderTrackingScrollViewDidScroll.swift

/*
Copyright 2016-present the Material Components for iOS authors. All Rights Reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

import XCTest
import MaterialComponents

// Tests confirming contract with a tracking scroll view that has scrolled
class FlexibleHeaderTrackingScrollViewDidScroll: XCTestCase {

  // Implicitly unwrapped to indicate the contract of creating these values in setUp and make our
  // accessors cleaner in tests.
  var view: MDCFlexibleHeaderView!
  var beforeFrame: CGRect!
  var scrollView: UIScrollView!

  override func setUp() {
    view = MDCFlexibleHeaderView()

    let originalFrame = CGRect(x: 0, y: 0, width: 100, height: 50)
    view.frame = originalFrame
    view.sizeToFit()

    beforeFrame = view.frame

    scrollView = UIScrollView()
    scrollView.contentSize = CGSize(width: originalFrame.size.width, height: 1000)
    scrollView.frame = CGRect(x: 0, y: 0, width: originalFrame.size.width, height: 250)

    view.trackingScrollView = scrollView
  }

  // MARK: Initial changes are ignored.

  func testFirstChangeDoesNothingNegative() {
    scrollView.setContentOffset(CGPoint(x: 0, y: -view.maximumHeight), animated: false)

    view.trackingScrollDidScroll()

    XCTAssertEqual(beforeFrame, view.frame)
  }

  func testFirstChangeDoesNothingPositive() {
    scrollView.setContentOffset(CGPoint(x: 0, y: 200), animated: false)

    view.trackingScrollDidScroll()

    XCTAssertEqual(beforeFrame, view.frame)
  }

  // MARK: Expansion on scroll to top.

  func testFullyExpandedOnScrollToTop() {
    view.trackingScrollDidScroll()

    view.maximumHeight = 200
    scrollView.setContentOffset(CGPoint(x: 0, y: -view.maximumHeight), animated: false)
    view.trackingScrollDidScroll()

    XCTAssertEqual(view.frame.size.height, view.maximumHeight)
  }
}