Add a test for inserting an empty collection in the middle

Author: karwa

Tests/SwiftAlgorithmsTests/ReplaceSubrangeTests.swift

@@ -94,11 +94,23 @@ final class ReplaceSubrangeTests: XCTestCase {
 
   func testInsert() {
 
-    let base = 0..<10
-    let i = base.index(base.startIndex, offsetBy: 5)
-    let result = base.lazy.replacingSubrange(i..<i, with: 20..<25)
-    XCTAssertEqualCollections(result, [0, 1, 2, 3, 4, 20, 21, 22, 23, 24, 5, 6, 7, 8, 9])
-    IndexValidator().validate(result, expectedCount: 15)
+    // Inserting: non-empty
+    do {
+      let base = 0..<10
+      let i = base.index(base.startIndex, offsetBy: 5)
+      let result = base.lazy.replacingSubrange(i..<i, with: 20..<25)
+      XCTAssertEqualCollections(result, [0, 1, 2, 3, 4, 20, 21, 22, 23, 24, 5, 6, 7, 8, 9])
+      IndexValidator().validate(result, expectedCount: 15)
+    }
+
+    // Inserting: empty
+    do {
+      let base = 0..<10
+      let i = base.index(base.startIndex, offsetBy: 5)
+      let result = base.lazy.replacingSubrange(i..<i, with: EmptyCollection())
+      XCTAssertEqualCollections(result, [0, 1, 2, 3, 4, 5, 6, 7, 8, 9])
+      IndexValidator().validate(result, expectedCount: 10)
+    }
   }
 
   func testReplace() {