In Salesforce, if you are trying to perform a Web Service Callout in a test class, you will get an error. For example:

public String sendHttpRequest(String endpointUrl, String method, DOM.Document body) {
  ...
  HttpRequest req = new HttpRequest();
  req.setEndpoint(endpointUrl);
  req.setMethod(method);
  req.setBody(bodyStr);

  Http http = new Http();
  HttpResponse res = http.send(req);

  return res.getBody();
}

When your test class runs untill line #9, it will stop the entire test process by throwing the following error:

System.TypeException: Methods defined as TestMethod do not support Web service callouts, test skipped callout

What if the overall test coverage is still under 75%? This will become a roadblock for your deployment. Below is the workaround you can consider:

public String sendHttpRequest(String endpointUrl, String method, DOM.Document body, Boolean isTest) {
  ...
  HttpRequest req = new HttpRequest();
  req.setEndpoint(endpointUrl);
  req.setMethod(method);
  req.setBody(bodyStr);

  Http http = new Http();
  if(isTest) {
    HttpResponse res = http.send(req);
    return res.getBody()
  } else {
    // You can prepare some simulated data for your test class here
    return simulatedData;
  }
}

By doing this, you can write different execution as below:

• Actual Process:
• You can call the sendHttpRequest method and set the isTest parameter to false.
• sendHttpRequest(‘your endpoint’, get, ‘http request body’, false);

• Test Process:
• In the test process, all you need to do is just set isTest to true.
• sendHttpRequest(‘your endpoint’, get, ‘http request body’, true);

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