     XCTAssertTrue(all.count == 5)
     XCTAssertTrue(all == [1, 3, 5, 7, 9])
   }
-  
+
   func test_removingAll() {
     let all = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10] // 11 elements
     let newAll = all.removingAll { (x) -> Bool in return (x.isEven)}
     XCTAssertTrue(newAll == [1, 3, 5, 7, 9])
     XCTAssertTrue(all.count == 11)
-    
   }
-  
-  
-//    func testPerformanceExample() {
-//      var array = [Int]()
-//      for i in stride(from: 0, to: 1_000_000, by: 1) {
-//        array.append(i)
-//      }
-//        self.measure {
-//          for _ in 1...10{
-//            let _ = array.removingLast(where: {$0 == 23})
-//          }
-//        }
-//    }
-  
+
+
+  func testPerformanceExample() {
+    var array = [Int]()
+    for i in stride(from: 0, to: 1_000_000, by: 1) {
+      array.append(i)
+    }
+    self.measure {
+      for _ in 1...10{
+        let _ = array.removingLast(where: {$0 == 23})
+      }
+    }
+  }
+
 }

    XCTAssertTrue(newAll == [1, 2, 3, 4, 5, 6, 7, 8, 9, 10])
    XCTAssertTrue(all.count == 11)
  }
  
  func test_removeLast() {
    var all = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10] // 11 elements
    /// removes the first even Int

@testable import Mechanica

class RangeReplaceableCollectionUtilsTests: XCTestCase {

  func test_removeFirst() {
    var all = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10] // 11 elements
    /// removes the first even Int
    let removedElement = all.removeFirst { (x) -> Bool in return (x.isEven) }
    XCTAssertNotNil(removedElement)
    XCTAssertTrue(removedElement! == 0)
    XCTAssertTrue(all.count == 10)
    XCTAssertTrue(all == [1, 2, 3, 4, 5, 6, 7, 8, 9, 10])
  }

  func test_removingFirst() {
    let all = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10] // 11 elements
