Cutting the Cord

When you test-drive, you create the seams that support your testing intent. Recognizing that the retrieve() method (Listing 14-2)

• Was a bit long

• Had no ready-made seams with which to sever the network connection for testing

• And performed a wide variety of low-level mechanics in support of its purpose

I decided to simplify and encapsulate it before continuing. Commit [c602d34] was the first application of this principle for WebRetriever.

Listing 14-2: The working but unwieldy and poorly testable first version of WebRetriever.retrieve()

Click here to view code image

public String retrieve(String URI) throws IOException {
  HttpClient httpClient = new DefaultHttpClient();
  HttpGet httpGet = new HttpGet(URI);
  HttpResponse response = httpClient.execute(httpGet);
  HttpEntity entity = response.getEntity();
  InputStream content = entity.getContent();
  StringWriter writer = new StringWriter();
  IOUtils.copy(content, writer);
  return writer.toString();
}

Looking at the method, you can categorize it as setup, execution, and response processing, very much like the first three phases of a test. Unlike a test, you do not need to preserve the boundaries between the phases when you refactor. I chose to extract the retrieval of the response, consisting of set up and execution, as a single method (Listing 14-3).

Listing 14-3: Refactoring the code from Listing 14-2 to provide a seam, allowing us to avoid the network connection for at least some of our tests [c602d34]

Click here to view code image

public String retrieve(String URI) throws IOException {
  HttpResponse response = retrieveResponse(URI);
  HttpEntity entity = response.getEntity();
  InputStream content = entity.getContent();
  StringWriter writer = new StringWriter();
  IOUtils.copy(content, writer);
  return writer.toString();
}

protected HttpResponse retrieveResponse(String URI)
    throws IOException {
  HttpClient httpClient = new DefaultHttpClient();
  HttpGet httpGet = new HttpGet(URI);
  return httpClient.execute(httpGet);
}

The following commits, through [c1d4b2f], use EasyMock to exploit the seam, although in an ugly and implementation-coupled way. That will be addressed in time. The commits through [b61f107] do some additional refactoring to improve both the test and the code under test in preparation for the next feature.