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MTKTestable.swift
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MTKTestable.swift
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//
// TestableViewController.swift
// MetovaTestKit
//
// Created by Nick Griffith on 5/7/16.
// Copyright © 2016 Metova. All rights reserved.
//
// MIT License
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//
/**
The MTKTestable protocol provides an alternative, functional approach to `XCTest`'s built in `setUp` & `tearDown` methods for handling unit tests.
`instanceForTesting()` should provide a new instance for each call.
`test(_:)` should effectively follow this pattern:
static func test(_ testBlock: (Self) -> Void) {
let testInstance = instanceForTesting()
// any code that would previously live in setUp
testBlock(testInstance)
// any code that would previously live in tearDown
}
With these methods implemented, our test cases now look like this:
func testThings() {
FooBarClass.test { testInstance in
XCTAssertNil(testInstance.thingThatShouldBeNil)
}
}
This allows `setUp` & `tearDown` code to exist across multiple files. Moreover, `setUp` & `tearDown` logic could now be inherited. As well, `MTKTestable` protocol extensions could be written to generalize some of the `setUp` & `tearDown` logic for large collections of types.
- Note
`UIViewController` and its subclasses get a free implementation of `test(_:)` as long as they have implemented `instanceForTesting()`. The default `test(_:)` implementation for view controllers calls `loadView()` and `viewDidLoad()` before running the `testBlock`.
*/
public protocol MTKTestable {
associatedtype TestableItem: Any
/**
Asks the `MTKTestable` type to run the given test block on an instance of the `MTKTestable` type.
- parameter testBlock: A block of code containing tests to run.
*/
static func test(_ testBlock: (TestableItem) -> Void)
/**
Asks the `MTKTestable` type for a new instance in order to be used for testing. This method should provide a new instance every time.
- returns: A new instance, ready for testing.
*/
static func instanceForTesting() -> Self
}