Add tests

Author: devxoul

Tests/SafeIndexTests.swift

@@ -40,4 +40,50 @@ class SafeIndexTests: XCTestCase {
         mutableArr[^2] = "D"
         XCTAssertEqual(mutableArr[^2], "D")
     }
+
+    func testSafeIndexMinus() {
+      XCTAssertEqual(^-5, ^(-5))
+    }
+
+    func testSafeIndexEquatable() {
+      XCTAssertTrue(^5 == ^5)
+      XCTAssertTrue(^3 == 3)
+      XCTAssertTrue(2 == ^2)
+    }
+
+    func testSafeIndexComparable() {
+      XCTAssertTrue(^5 > ^4)
+      XCTAssertTrue(5 > 4)
+      XCTAssertTrue(5 > ^4)
+
+      XCTAssertTrue(^3 >= ^3)
+      XCTAssertTrue(^3 >= 3)
+      XCTAssertTrue(3 >= ^3)
+
+      XCTAssertTrue(^4 < ^6)
+      XCTAssertTrue(^4 < 6)
+      XCTAssertTrue(4 < ^6)
+
+      XCTAssertTrue(^6 <= ^6)
+      XCTAssertTrue(^6 <= 6)
+      XCTAssertTrue(6 <= ^6)
+    }
+
+    func testSafeIndexArithmetic() {
+      XCTAssertEqual(^5, ^2 + ^3)
+      XCTAssertEqual(^11, ^10 + 1)
+      XCTAssertEqual(^12, 2 + ^10)
+
+      XCTAssertEqual(^1, ^3 - ^2)
+      XCTAssertEqual(^9, ^10 - 1)
+      XCTAssertEqual(^3, 11 - ^8)
+
+      XCTAssertEqual(^6, ^2 * ^3)
+      XCTAssertEqual(^20, ^10 * 2)
+      XCTAssertEqual(^30, 3 * ^10)
+
+      XCTAssertEqual(^2, ^6 / ^3)
+      XCTAssertEqual(^3, ^10 / 3)
+      XCTAssertEqual(^6, 20 / ^3)
+    }
 }