Add partial sort tests

Author: rakaramos

Tests/SwiftAlgorithmsTests/PartialSortTests.swift

@@ -0,0 +1,106 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift Algorithms open source project
+//
+// Copyright (c) 2020 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
+import XCTest
+import Algorithms
+
+final class PartialSortTests: XCTestCase {
+  func testEmpty() {
+    let array = [Int]()
+
+    XCTAssertEqual(array.partiallySorted(0), [])
+  }
+
+  func testPartialSortComparable() {
+    let array: [Int] = [20, 1, 4, 70, 100, 2, 3, 7, 90]
+
+    XCTAssertEqual(array.partiallySorted(0), array)
+
+    XCTAssertEqual(
+      array.partiallySorted(1),
+      [1, 90, 4, 70, 100, 7, 3, 2, 20]
+    )
+
+    XCTAssertEqual(
+      array.partiallySorted(5),
+      [1, 2, 3, 4, 7, 90, 70, 20, 100]
+    )
+
+    XCTAssertEqual(
+      array.partiallySorted(9),
+      [1, 2, 3, 4, 7, 20, 70, 90, 100]
+    )
+  }
+
+  func testPartialSortComparableWithCustomPriority() {
+    let array: [Int] = [20, 1, 4, 70, 100, 2, 3, 7, 90]
+
+    XCTAssertEqual(array.partiallySorted(0, by: >), array)
+    XCTAssertEqual(
+      array.partiallySorted(1, by: >),
+      [100, 1, 4, 3, 7, 20, 70, 90, 2]
+    )
+
+    XCTAssertEqual(
+      array.partiallySorted(5, by: >),
+      [100, 90, 70, 20, 7, 2, 4, 3, 1]
+    )
+
+    XCTAssertEqual(
+      array.partiallySorted(9, by: >),
+      [100, 90, 70, 20, 7, 4, 3, 2, 1]
+    )
+  }
+
+  func testPartialSortInPlaceComparable() {
+    let originalArray: [Int] = [20, 1, 4, 70, 100, 2, 3, 7, 90]
+    var array = originalArray
+
+    array.partiallySort(0)
+    XCTAssertEqual(array, originalArray)
+
+    array = originalArray
+
+    array.partiallySort(1)
+    XCTAssertEqual(
+      array,
+      [1, 90, 4, 70, 100, 7, 3, 2, 20]
+    )
+
+    array = originalArray
+
+    array.partiallySort(5)
+    XCTAssertEqual(
+      array,
+      [1, 2, 3, 4, 7, 90, 70, 20, 100]
+    )
+
+    array = originalArray
+
+    array.partiallySort(9)
+    XCTAssertEqual(
+      array,
+      [1, 2, 3, 4, 7, 20, 70, 90, 100]
+    )
+  }
+
+  func testPartialSortDescendingArray() {
+    let array: [Int] = [100, 90, 70, 20, 7, 4, 3, 2, 1]
+
+    XCTAssertEqual(array.partiallySorted(9, by: >), array)
+  }
+
+  func testPartialSortAscendingArray() {
+    let array: [Int] = [1, 2, 3, 4, 7, 20, 70, 90, 100]
+
+    XCTAssertEqual(array.partiallySorted(9, by: <), array)
+  }
+}