A class to stub network requests easily: test your apps with fake network data (stubbed from file) and custom response time

• Basic Usage
• The OHHTTPStubsResponse object
• Advanced Usage
• Return a response depending on the request
• Using download speed instead of responseTime
• Return quickly when onlyCheck=YES
• Stack multiple requestHandlers
• Complete Examples
• Using in your projects
• Change Log
• License and Credits

This is aimed to be very simple to use. It uses block to intercept outgoing requests and allow you to return data from a file instead.

This is the most simple way to use it:

[OHHTTPStubs addRequestHandler:^OHHTTPStubsResponse*(NSURLRequest *request, BOOL onlyCheck)
 {
   return [OHHTTPStubsResponse responseWithFile:@"response.json" contentType:@"text/json" responseTime:2.0];
 }];

This will return the NSData corresponding to the content of the "response.json" file (that must be in your bundle) with a "Content-Type" header of "text/json" in the HTTP response, after 2 seconds.

Each time a network request is done by your application (whatever the framework used, NSURLConnection, AFNetworking, or anything else) this requestHandler block will be called, allowing you to return an OHHTTPStubsResponse object describing the response to return. If you return a non-nil OHHTTPStubsResponse, it will automatically build a NSURLResponse and behave exactly like if you received the response from the network. If your return nil, the normal request will be sent.

The OHHTTPStubsResponse class exposes multiple initializers:

+(id)responseWithData:(NSData*)data
           statusCode:(int)statusCode
         responseTime:(NSTimeInterval)responseTime
              headers:(NSDictionary*)httpHeaders;

+(id)responseWithFile:(NSString*)fileName
           statusCode:(int)statusCode
         responseTime:(NSTimeInterval)responseTime
              headers:(NSDictionary*)httpHeaders;

+(id)responseWithFile:(NSString*)fileName
          contentType:(NSString*)contentType
         responseTime:(NSTimeInterval)responseTime;

+(id)responseWithError:(NSError*)error;

(e.g. you could use an error like [NSError errorWithDomain:NSURLErrorDomain code:404 userInfo:nil])

Of course, and that's the main reason this is implemented with blocks, you can do whatever you need in the block implementation. This includes checking the request URL to see if you want to return a stub or not, and pick the right file according to the requested URL.

Example:

[OHHTTPStubs addRequestHandler:^OHHTTPStubsResponse*(NSURLRequest *request, BOOL onlyCheck)
 {
   if ([request.URL.absoluteString hasPrefix:@".json"]) {
     NSString* basename = [request.URL.absoluteString lastPathComponent]
     return [OHHTTPStubsResponse responseWithFile:basename contentType:@"text/json" responseTime:2.0];
   } else {
     return nil; // Don't stub
   }
 }];

When building the OHHTTPStubsResponse object, you can specify a response time (in seconds) so that the sending of the fake response will be postponed (using GCD's dispatch_after function). This allows you to simulate a slow network for example.

If you specify a negative value for the responseTime parameter, instead of being interpreted as a time in seconds, it will be interpreted as a download speed in KBytes/s. In that case, the response time will be computed using the size of the response's data to simulate the indicated download speed.

The OHHTTPStubsResponse header defines some constants for standard download speeds:

• OHHTTPStubsDownloadSpeedGPRS : 56 kbps (7 KB/s)
• OHHTTPStubsDownloadSpeedEDGE : 128 kbps (16 KB/s)
• OHHTTPStubsDownloadSpeed3G : 3200 kbps (400 KB/s)
• OHHTTPStubsDownloadSpeed3GPlus : 7200 kbps (900 KB/s)
• OHHTTPStubsDownloadSpeedWifi : 12000 kbps (1500 KB/s)

If the onlyCheck parameter of the requestHandler block is YES, then it means that the handler is called only to check if you will be able to return a stubbed response or if it has to do the standard request. In this scenario, the response will not actually be used but will only be compared to nil to check if it has to be stubbed later. The handler will be called later again (with onlyCheck=NO) to fetch the actual OHHTTPStubsResponse object.

So in such cases (onlyCheck==YES), you can simply return nil if you don't want to provide a stubbed response, and any non-nil value to indicate that you will provide a stubbed response later.

This may be useful if you intend to do some not-so-fast work to build your real OHHTTPStubsResponse (like reading some large file for example): in that case you can quickly return a dummy value when onlyCheck==YES without the burden of building the actual OHHTTPStubsResponse object. You will obviously return the real OHHTTPStubsResponse in the later call when onlyCheck==NO.

There is a macro OHHTTPStubsResponseUseStub provided in the header that you can use as a dummy return value for that purpose (it actually evaluates to (OHHTTPStubsReponse*)1)

You can call +addRequestHandler: multiple times. It will just add the response handlers in an internal list of handler.

When a network request is performed by the system, the response handlers are called in the reverse order that they have been added, the last added handler having priority over the first added ones. The first non-nil OHHTTPStubsResponse returned is used to reply to the request.

This may be useful to install different stubs in different classes (say different UIViewControllers) and various places in your application.

You can remove the latest added handler with the removeLastRequestHandler method.

You can also remove any given handler with the removeRequestHandler: method. This method takes as a parameter the object returned by addRequestHandler:. Note that this returned object is already retained by OHHTTPStubs, so you may keep it in a __weak variable.

Here is another example code below that uses the various techniques explained above. For a complete Xcode projet, see the OHHTTPStubsDemo.xcworkspace project in the repository.

NSArray* stubs = [NSArray arrayWithObjects:@"file1", @"file2", nil];
                       
[OHHTTPStubs addRequestHandler:^OHHTTPStubsResponse*(NSURLRequest *request, BOOL onlyCheck)
 {
     NSString* basename = [request.URL.absoluteString lastPathComponent];
     if (onlyCheck) {
         return ([stubs containsObject:basename] ? OHHTTPStubsResponseUseStub : nil);
     }
     
     NSString* file = [basename stringByAppendingPathExtension:@"json"];
     return [OHHTTPStubsResponse responseWithFile:file contentType:@"text/json"
                                     responseTime:OHHTTPStubsDownloadSpeedEDGE];
 }];
 
 ...
 
// Then this call (sending a request using the AFNetworking framework) will actually
// receive a fake response issued from the file "file1.json"
NSURLRequest* request = [NSURLRequest requestWithURL:[NSURL URLWithString:@"http://www.example.com/file1"]];
AFJSONRequestOperation* req =
[AFJSONRequestOperation JSONRequestOperationWithRequest:request success:^(NSURLRequest *request, NSHTTPURLResponse *response, id JSON)
 {
    ...
 } failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error, id JSON)
 {
    ...
 }];
[req start];

The OHHTTPStubs project is provided as a Xcode project that generates a static library, to easily integrate it with your project.

• Add the OHHTTPStubs.xcodeproj project to your application workspace, next to your application project
• Link libOHHTTPStubs.a with your application project
• When you need to use OHHTTPStubs classes, import the headers using square brackets: #import <OHHTTPStubs/OHHTTPStubs.h>

Note: due to a bug in Xcode4, you will have to ensure that the libOHHTTPStubs.a file reference added in your project has its path referenced as "Relative to Build Products" as it should. If it is not the case, please read the detailed instructions here.

The changelog is available here in the dedicated wiki page.

This project is brought to you by Olivier Halligon and is under MIT License

It has been inspired by this article from InfiniteLoop.dk (See also his GitHub repository)