Add Swift unit test and usage example to Readme

Readme.markdown

@@ -171,6 +171,12 @@ Rust language:
         }
     }
 
+Swift language:
+
+    import QRCodeGenerator
+    
+    let qr = try! QRCode.encode(text: text, ecl: .medium)
+    let svg = qr.toSVGString(border: 4)
 
 License
 -------

swift/Tests/QRCodeGeneratorTests/QRCodeGeneratorTests.swift

@@ -1,15 +1,48 @@
+/* 
+ * QR Code generator library (Swift)
+ * 
+ * Copyright (c) Project Nayuki. (MIT License)
+ * https://www.nayuki.io/page/qr-code-generator-library
+ * 
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to
+ * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+ * the Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ * - The above copyright notice and this permission notice shall be included in
+ *   all copies or substantial portions of the Software.
+ * - The Software is provided "as is", without warranty of any kind, express or
+ *   implied, including but not limited to the warranties of merchantability,
+ *   fitness for a particular purpose and noninfringement. In no event shall the
+ *   authors or copyright holders be liable for any claim, damages or other
+ *   liability, whether in an action of contract, tort or otherwise, arising from,
+ *   out of or in connection with the Software or the use or other dealings in the
+ *   Software.
+ */
+
 import XCTest
 @testable import QRCodeGenerator
 
 final class QRCodeGeneratorTests: XCTestCase {
-    func testExample() {
-        // This is an example of a functional test case.
-        // Use XCTAssert and related functions to verify your tests produce the correct
-        // results.
-        XCTAssertEqual(QRCodeGenerator().text, "Hello, World!")
-    }
-
     static var allTests = [
-        ("testExample", testExample),
+        ("testQRCodeGeneration", testQRCodeGeneration),
     ]
+
+    func testQRCodeGeneration() throws {
+        // Tested against the JS implementation using https://www.nayuki.io/page/qr-code-generator-library
+
+        let text = "test"
+        let qr = try QRCode.encode(text: text, ecl: .low)
+        let svg = qr.toSVGString(border: 4)
+
+        XCTAssertEqual(svg, """
+            <?xml version="1.0" encoding="UTF-8"?>
+            <!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
+            <svg xmlns="http://www.w3.org/2000/svg" version="1.1" viewBox="0 0 29 29" stroke="none">
+              <rect width="100%" height="100%" fill="#FFFFFF"/>
+              <path d="M4,4h1v1h-1z M5,4h1v1h-1z M6,4h1v1h-1z M7,4h1v1h-1z M8,4h1v1h-1z M9,4h1v1h-1z M10,4h1v1h-1z M12,4h1v1h-1z M13,4h1v1h-1z M14,4h1v1h-1z M16,4h1v1h-1z M18,4h1v1h-1z M19,4h1v1h-1z M20,4h1v1h-1z M21,4h1v1h-1z M22,4h1v1h-1z M23,4h1v1h-1z M24,4h1v1h-1z M4,5h1v1h-1z M10,5h1v1h-1z M13,5h1v1h-1z M14,5h1v1h-1z M18,5h1v1h-1z M24,5h1v1h-1z M4,6h1v1h-1z M6,6h1v1h-1z M7,6h1v1h-1z M8,6h1v1h-1z M10,6h1v1h-1z M14,6h1v1h-1z M18,6h1v1h-1z M20,6h1v1h-1z M21,6h1v1h-1z M22,6h1v1h-1z M24,6h1v1h-1z M4,7h1v1h-1z M6,7h1v1h-1z M7,7h1v1h-1z M8,7h1v1h-1z M10,7h1v1h-1z M12,7h1v1h-1z M15,7h1v1h-1z M16,7h1v1h-1z M18,7h1v1h-1z M20,7h1v1h-1z M21,7h1v1h-1z M22,7h1v1h-1z M24,7h1v1h-1z M4,8h1v1h-1z M6,8h1v1h-1z M7,8h1v1h-1z M8,8h1v1h-1z M10,8h1v1h-1z M14,8h1v1h-1z M15,8h1v1h-1z M18,8h1v1h-1z M20,8h1v1h-1z M21,8h1v1h-1z M22,8h1v1h-1z M24,8h1v1h-1z M4,9h1v1h-1z M10,9h1v1h-1z M13,9h1v1h-1z M15,9h1v1h-1z M18,9h1v1h-1z M24,9h1v1h-1z M4,10h1v1h-1z M5,10h1v1h-1z M6,10h1v1h-1z M7,10h1v1h-1z M8,10h1v1h-1z M9,10h1v1h-1z M10,10h1v1h-1z M12,10h1v1h-1z M14,10h1v1h-1z M16,10h1v1h-1z M18,10h1v1h-1z M19,10h1v1h-1z M20,10h1v1h-1z M21,10h1v1h-1z M22,10h1v1h-1z M23,10h1v1h-1z M24,10h1v1h-1z M13,11h1v1h-1z M16,11h1v1h-1z M6,12h1v1h-1z M8,12h1v1h-1z M9,12h1v1h-1z M10,12h1v1h-1z M12,12h1v1h-1z M13,12h1v1h-1z M17,12h1v1h-1z M21,12h1v1h-1z M24,12h1v1h-1z M7,13h1v1h-1z M8,13h1v1h-1z M11,13h1v1h-1z M12,13h1v1h-1z M16,13h1v1h-1z M18,13h1v1h-1z M19,13h1v1h-1z M23,13h1v1h-1z M24,13h1v1h-1z M4,14h1v1h-1z M5,14h1v1h-1z M6,14h1v1h-1z M7,14h1v1h-1z M8,14h1v1h-1z M10,14h1v1h-1z M12,14h1v1h-1z M16,14h1v1h-1z M17,14h1v1h-1z M18,14h1v1h-1z M19,14h1v1h-1z M21,14h1v1h-1z M22,14h1v1h-1z M23,14h1v1h-1z M24,14h1v1h-1z M4,15h1v1h-1z M5,15h1v1h-1z M6,15h1v1h-1z M7,15h1v1h-1z M9,15h1v1h-1z M12,15h1v1h-1z M13,15h1v1h-1z M15,15h1v1h-1z M16,15h1v1h-1z M19,15h1v1h-1z M20,15h1v1h-1z M23,15h1v1h-1z M4,16h1v1h-1z M5,16h1v1h-1z M9,16h1v1h-1z M10,16h1v1h-1z M12,16h1v1h-1z M13,16h1v1h-1z M14,16h1v1h-1z M19,16h1v1h-1z M21,16h1v1h-1z M23,16h1v1h-1z M24,16h1v1h-1z M12,17h1v1h-1z M14,17h1v1h-1z M15,17h1v1h-1z M16,17h1v1h-1z M21,17h1v1h-1z M24,17h1v1h-1z M4,18h1v1h-1z M5,18h1v1h-1z M6,18h1v1h-1z M7,18h1v1h-1z M8,18h1v1h-1z M9,18h1v1h-1z M10,18h1v1h-1z M13,18h1v1h-1z M14,18h1v1h-1z M20,18h1v1h-1z M21,18h1v1h-1z M23,18h1v1h-1z M24,18h1v1h-1z M4,19h1v1h-1z M10,19h1v1h-1z M12,19h1v1h-1z M13,19h1v1h-1z M14,19h1v1h-1z M16,19h1v1h-1z M18,19h1v1h-1z M23,19h1v1h-1z M4,20h1v1h-1z M6,20h1v1h-1z M7,20h1v1h-1z M8,20h1v1h-1z M10,20h1v1h-1z M12,20h1v1h-1z M14,20h1v1h-1z M15,20h1v1h-1z M18,20h1v1h-1z M20,20h1v1h-1z M21,20h1v1h-1z M23,20h1v1h-1z M24,20h1v1h-1z M4,21h1v1h-1z M6,21h1v1h-1z M7,21h1v1h-1z M8,21h1v1h-1z M10,21h1v1h-1z M13,21h1v1h-1z M18,21h1v1h-1z M19,21h1v1h-1z M23,21h1v1h-1z M4,22h1v1h-1z M6,22h1v1h-1z M7,22h1v1h-1z M8,22h1v1h-1z M10,22h1v1h-1z M12,22h1v1h-1z M16,22h1v1h-1z M17,22h1v1h-1z M19,22h1v1h-1z M22,22h1v1h-1z M24,22h1v1h-1z M4,23h1v1h-1z M10,23h1v1h-1z M13,23h1v1h-1z M14,23h1v1h-1z M15,23h1v1h-1z M17,23h1v1h-1z M18,23h1v1h-1z M19,23h1v1h-1z M20,23h1v1h-1z M21,23h1v1h-1z M23,23h1v1h-1z M4,24h1v1h-1z M5,24h1v1h-1z M6,24h1v1h-1z M7,24h1v1h-1z M8,24h1v1h-1z M9,24h1v1h-1z M10,24h1v1h-1z M14,24h1v1h-1z M17,24h1v1h-1z M18,24h1v1h-1z M19,24h1v1h-1z M22,24h1v1h-1z M23,24h1v1h-1z M24,24h1v1h-1z" fill="#000000"/>
+            </svg>
+            """)
+    }
 }