Add laziness tests

Author: timvermeulen

Tests/SwiftAlgorithmsTests/ChainTests.swift

@@ -136,4 +136,8 @@ final class ChainTests: XCTestCase {
       XCTAssertEqual(chain.distance(from: start, to: end), distance)
     }
   }
+  
+  func testChainLazy() {
+    XCTAssertLazy([1, 2, 3].lazy.chained(with: [4, 5, 6]))
+  }
 }

Tests/SwiftAlgorithmsTests/ChunkedTests.swift

@@ -71,4 +71,9 @@ final class ChunkedTests: XCTestCase {
     let lazyChunks = fruits.lazy.chunked(by: { $0.first == $1.first })
     validateFruitChunks(lazyChunks)
   }
+  
+  func testChunkedLazy() {
+    XCTAssertLazy(fruits.lazy.chunked(by: { $0.first == $1.first }))
+    XCTAssertLazy(fruits.lazy.chunked(on: { $0.first }))
+  }
 }

Tests/SwiftAlgorithmsTests/CombinationsTests.swift

@@ -38,4 +38,8 @@ final class CombinationsTests: XCTestCase {
     XCTAssertEqualSequences([], "".combinations(ofCount: 5))
     XCTAssertEqualSequences([], "ABCD".combinations(ofCount: 5))
   }
+  
+  func testCombinationsLazy() {
+    XCTAssertLazy("ABC".lazy.combinations(ofCount: 1))
+  }
 }

Tests/SwiftAlgorithmsTests/CycleTests.swift

@@ -39,4 +39,8 @@ final class CycleTests: XCTestCase {
     let empty2 = Array("Hello".cycled(times: 0))
     XCTAssert(empty2.isEmpty)
   }
+  
+  func testCycleLazy() {
+    XCTAssertLazy((1...4).lazy.cycled())
+  }
 }

Tests/SwiftAlgorithmsTests/IndexedTests.swift

@@ -27,4 +27,8 @@ final class IndexedTests: XCTestCase {
     let indexOfI = si.last(where: { $0.element == "I" })!.index
     XCTAssertEqual("I", s[indexOfI])
   }
+  
+  func testIndexedLazy() {
+    XCTAssertLazy("ABCD".lazy.indexed())
+  }
 }

Tests/SwiftAlgorithmsTests/PermutationsTests.swift

@@ -69,4 +69,8 @@ final class PermutationsTests: XCTestCase {
     while numbers.nextPermutation() {}
     XCTAssertEqual([1, 2, 3, 4, 5, 6, 7], numbers)
   }
+  
+  func testPermutationsLazy() {
+    XCTAssertLazy("ABCD".lazy.permutations(ofCount: 2))
+  }
 }

Tests/SwiftAlgorithmsTests/TestUtilities.swift

@@ -65,3 +65,4 @@ func XCTAssertEqualSequences<S1: Sequence, S2: Sequence>(
   try XCTAssert(expression1().elementsEqual(expression2(), by: areEquivalent), message(), file: file, line: line)
 }
 
+func XCTAssertLazy<S: LazySequenceProtocol>(_: S) {}