QueueTests.swift

import Foundation
import XCTest

class QueueTest: XCTestCase {
  func testEmpty() {
    var queue = Queue<Int>()
    XCTAssertTrue(queue.isEmpty)
    XCTAssertEqual(queue.count, 0)
    XCTAssertEqual(queue.front, nil)
    XCTAssertNil(queue.dequeue())
  }

  func testOneElement() {
    var queue = Queue<Int>()

    queue.enqueue(123)
    XCTAssertFalse(queue.isEmpty)
    XCTAssertEqual(queue.count, 1)
    XCTAssertEqual(queue.front, 123)

    let result = queue.dequeue()
    XCTAssertEqual(result, 123)
    XCTAssertTrue(queue.isEmpty)
    XCTAssertEqual(queue.count, 0)
    XCTAssertEqual(queue.front, nil)
  }

  func testTwoElements() {
    var queue = Queue<Int>()

    queue.enqueue(123)
    queue.enqueue(456)
    XCTAssertFalse(queue.isEmpty)
    XCTAssertEqual(queue.count, 2)
    XCTAssertEqual(queue.front, 123)

    let result1 = queue.dequeue()
    XCTAssertEqual(result1, 123)
    XCTAssertFalse(queue.isEmpty)
    XCTAssertEqual(queue.count, 1)
    XCTAssertEqual(queue.front, 456)

    let result2 = queue.dequeue()
    XCTAssertEqual(result2, 456)
    XCTAssertTrue(queue.isEmpty)
    XCTAssertEqual(queue.count, 0)
    XCTAssertEqual(queue.front, nil)
  }

  func testMakeEmpty() {
    var queue = Queue<Int>()

    queue.enqueue(123)
    queue.enqueue(456)
    XCTAssertNotNil(queue.dequeue())
    XCTAssertNotNil(queue.dequeue())
    XCTAssertNil(queue.dequeue())

    queue.enqueue(789)
    XCTAssertEqual(queue.count, 1)
    XCTAssertEqual(queue.front, 789)

    let result = queue.dequeue()
    XCTAssertEqual(result, 789)
    XCTAssertTrue(queue.isEmpty)
    XCTAssertEqual(queue.count, 0)
    XCTAssertEqual(queue.front, nil)
  }
}