CODEWITHSUNDEEP
javaapitestingmockingcurrency
Gohan255
Gohan255

Reputation: 1

How do I test currency exchange method with API?

I have problem with testing my method for currency exchange from API. I have no idea how to do testings to this method as I can't predict what currency rates are at the moment, they are changing every second. My teacher told me that I have to do another method that testing my first one and then Mock something. Please guys help.

public class CurrencyService {


    private static HttpURLConnection conn;

    private Pattern currencyPattern;

    public double exchange(String currencyFrom, String currencyTo, double amount) {
        currencyPattern = Pattern.compile("[A-Z]{3}");

        if (!currencyPattern.matcher(currencyFrom).matches() || !currencyPattern.matcher(currencyTo).matches()) {
            throw new BadPatternForCurrency("Currency FROM and TO must be for example: Dollar USD, euro EUR etc.");
        }

        if (amount < 0) {
            throw new NoMinusValuesInAmountException("Amonut must be more than 0!");
        }

        DecimalFormat df = new DecimalFormat("##.##");
        String adres = "https://api.apilayer.com/exchangerates_data/";
        BufferedReader reader;
        String line;
        StringBuilder responseContent = new StringBuilder();
        try {
            URL url = new URL(adres + "convert?to=" + currencyTo.toUpperCase() + "&from=" + currencyFrom.toUpperCase() + "&amount=" + amount);
            conn = (HttpURLConnection) url.openConnection();

            conn.setRequestMethod("GET");
            conn.setRequestProperty("apikey", "tSaLWidFRzgzO2mGNfFgVEIr2cqeWCUY");

            int status = conn.getResponseCode();

            if (status != 200) {
                reader = new BufferedReader(new InputStreamReader(conn.getErrorStream()));
                while ((line = reader.readLine()) != null) {
                    responseContent.append(line);
                }
                reader.close();
            } else {
                reader = new BufferedReader(new InputStreamReader(conn.getInputStream()));
                while ((line = reader.readLine()) != null) {
                    responseContent.append(line);
                }
                reader.close();
            }
        } catch (ProtocolException e) {
            e.printStackTrace();
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }


        JSONObject obj = new JSONObject(responseContent.toString());
        double result = obj.getDouble("result");

        return result;

    }
}

Upvotes: 0

Views: 458

Answers (1)

Vitaly Chura
Vitaly Chura

Reputation: 870

To elaborate on @tgdavies comment:

You should better move everything starting with: BufferedReader reader; into a separate class, for example, ExchangeApiClient and provide that class into your CurrencyService via a constructor. That ExchangeApiClient should return a string, so everything left to your service is to create a call exchangeApiClient.getResponse().

This way you will be able to unit-test your currency service.

The question remains how to test your ExchangeApiClient - that can also be done. You must create a HttpConnectionFactory and pass that factory via a constructor to your ExchangeApiClient. You should also make it non-static. Then you can pass a mock connection, which returns mock inputStream, you can here more about that here

If you want to read something about mocking I recommend a book "Practical Unit Testing with JUnit and Mockito".

Upvotes: 1

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