         XCTAssert (100000000 == btc3s.double (as: BTC_SATOSHI))
         XCTAssert (1         == btc3s.double (as: BTC_BTC))
 
-        XCTAssertEqual ("SAT 100,000,000", btc3s.string (as: BTC_SATOSHI)!)
-        XCTAssertEqual ("B 1.00",          btc3s.string (as: BTC_BTC)!)
+        if #available(iOS 13, *) {
+            XCTAssertEqual ("SAT 100,000,000", btc3s.string (as: BTC_SATOSHI)!)
+            XCTAssertEqual ("B 1.00",          btc3s.string (as: BTC_BTC)!)
+        }
+        else {
+            XCTAssertEqual ("SAT100,000,000", btc3s.string (as: BTC_SATOSHI)!)
+            XCTAssertEqual ("B1.00",          btc3s.string (as: BTC_BTC)!)
+        }
 
         let btc4s = Amount.create (string: "0x5f5e100", negative: true, unit: BTC_SATOSHI)!
         XCTAssert (-100000000 == btc4s.double (as: BTC_SATOSHI))
         XCTAssert (-1         == btc4s.double (as: BTC_BTC))
-        XCTAssertEqual ("-SAT 100,000,000", btc4s.string (as: BTC_SATOSHI)!)
-        XCTAssertEqual ("-B 1.00",          btc4s.string (as: BTC_BTC)!)
+
+        if #available(iOS 13, *) {
+            XCTAssertEqual ("-SAT 100,000,000", btc4s.string (as: BTC_SATOSHI)!)
+            XCTAssertEqual ("-B 1.00",          btc4s.string (as: BTC_BTC)!)
+        }
+        else {
+            XCTAssertEqual ("-SAT100,000,000", btc4s.string (as: BTC_SATOSHI)!)
+            XCTAssertEqual ("-B1.00",          btc4s.string (as: BTC_BTC)!)
+        }
 
         XCTAssertNil (Amount.create (string: "w0x5f5e100", unit: BTC_SATOSHI))
         XCTAssertNil (Amount.create (string: "0x5f5e100w", unit: BTC_SATOSHI))

        XCTAssert (-1.5       == btc4.double (as: BTC_BTC))
        XCTAssert (-150000000 == btc4.double (as: BTC_SATOSHI))

        XCTAssertEqual ("-B 1.50", btc4.string (as: BTC_BTC))
        XCTAssertEqual ("-SAT 150,000,000", btc4.string (as: BTC_SATOSHI)!)

        XCTAssertEqual (btc1.double(as: BTC_BTC),     btc1.convert(to: BTC_SATOSHI)?.double(as: BTC_BTC))
        XCTAssertEqual (btc1.double(as: BTC_SATOSHI), btc1.convert(to: BTC_BTC)?.double(as: BTC_SATOSHI))

        XCTAssertNotNil (a5?.double(as: ETH_WEI))
        XCTAssertEqual(1234567891234567891, a5?.double(as: ETH_WEI)!)
        // Lost precision - last 5 digits
        if #available(iOS 13, *) {
            XCTAssertEqual("wei 1,234,567,891,234,568,000", a5?.string(as: ETH_WEI)!)
        }
        else {
            XCTAssertEqual("wei1,234,567,891,234,570,000", a5?.string(as: ETH_WEI)!)
        }

        XCTAssertEqual("1234567891234567891", a5?.string (base: 10, preface: ""))
        XCTAssertEqual("1000000000000000000", Amount.create(string: "1", negative: false, unit: ETH_ETHER)!.string (base: 10, preface: ""))
