Tag: mocks

I want to write testable code and occasionally I bump into frameworks that make it challenging to unit test. Ideally I want to inject a service stub into my code then control the stub’s behavior based on my testing needs.
Commons Http Client from Jakarta facilitates integration with HTTP services but how to easily unit test code that depends on the HttpClient library? Turns out it’s not that hard.
I’ll cover both 1.3 and the newer 1.4 versions of the library since the older v1.3 is still widely used.
Here’s some typical service (HttpClient v1.3) we want to test. It returns the remote HTML page title:

public class RemoteHttpService {
   private HttpClient client;
   
   public String getPageTitle(String uri)  throws IOException {
     String contentHtml = fetchContent(uri);
     Pattern p = Pattern.compile("<title>(.*)</title>");
     Matcher m = p.matcher(contentHtml);
     if(m.find()) {
        return m.group(1);
     }
     return null;
   }

   private String fetchContent(String uri)  throws IOException {
      HttpMethod method = new GetMethod("http://blog.newsplore.com/" + uri);
      int responseStatus = client.executeMethod(method);
      if(responseStatus != 200) {
        throw new IllegalStateException("Expected HTTP response status 200 " +
"but instead got [" + responseStatus + "]");
      }
      byte[] responseBody = method.getResponseBody();
      return new String(responseBody, "UTF-8");
   }

   public void setHttpClient(HttpClient client) {
      this.client = client;
   }
}

with the HttpClient is injected at runtime (via some IoC container or explicitly).
To be able to unit-test this code we have to come-up with a stubbed version of the HttpClient and emulate the GET method.

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