OHHTTPStubs

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

OHHTTPStubs is very useful to write Unit Tests and return fake network data from your fixtures, or to simulate slow networks in order to check your application behavior in bad network conditions. It works with NSURLConnection, AFNetworking, or any networking framework you chose to use.

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• How it works
• Documentation
• Usage examples
  • Stub all requests with some given NSData
  • Stub only requests to your WebService
  • Set request and response time
  • Simulate a down network
• Advanced Usage
  • Use macros to build your fixtures path
  • Using download speed instead of responseTime
  • Stack multiple stubs and remove installed stubs
  • Name your stubs and log their activation
  • OHHTTPStubs and NSURLSession
• Installing in your projects
• About OHHTTPStubs Unit Tests
• Change Log
• License and Credits

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How it works

Using OHHTTPStubs is as simple as calling stubRequestsPassingTest:withStubResponse: to tell which requests you want to stub and what data you want to respond with.

For every request sent to the network, whatever the framework used (NSURLConnection, AFNetworking, …):

• The block passed as first argument of stubRequestsPassingTest:withStubResponse: will be called to check if we need to stub this request.
• If the return value of this block is YES, the block passed as second argument will be called to let you return an OHHTTPStubsResponse object, describing the fake response to return.

(In practice, it uses the URL Loading System of Cocoa and a custom NSURLProtocol to intercept the requests and stub them)

Documentation

OHHTTPStubs headers are fully documented using Appledoc-like / Headerdoc-like comments in the header files. When you install it using CocoaPods, you will get a docset for free installed in your Xcode Organizer.

Don't hesitate to take a look into OHHTTPStubsResponse.h, OHHTTPStubsResponse+JSON.h and OHHTTPStubsResponse.HTTPMessage.h to see all the commodity constructors, constants and macros available.

Usage examples

Stub all requests with some given NSData

With the code below, every network request (because you returned YES in the first block) will return a stubbed response containing the data "Hello World!":

[OHHTTPStubs stubRequestsPassingTest:^BOOL(NSURLRequest *request) {
    return YES; // Stub ALL requests without any condition
} withStubResponse:^OHHTTPStubsResponse*(NSURLRequest *request) {
    // Stub all those requests with "Hello World!" string
    NSData* stubData = [@"Hello World!" dataUsingEncoding:NSUTF8StringEncoding];
    return [OHHTTPStubsResponse responseWithData:stubData statusCode:200 headers:nil];
}];

Stub only requests to your WebService

This is typically useful in your Unit Tests to only stub specific requests targeted to a given host or WebService, for example.

With the code below, only requests to the mywebservice.com host will be stubbed. Requests to any other host will hit the real world:

[OHHTTPStubs stubRequestsPassingTest:^BOOL(NSURLRequest *request) {
    return [request.URL.host isEqualToString:@"mywebservice.com"];
} withStubResponse:^OHHTTPStubsResponse*(NSURLRequest *request) {
    // Stub it with our "wsresponse.json" stub file
    return [OHHTTPStubsResponse responseWithFileAtPath:OHPathForFileInBundle(@"wsresponse.json",nil)
            statusCode:200 headers:@{@"Content-Type":@"text/json"}];
}];

This example also demonstrate how to easily return the content of a given file in your application bundle. This is useful if you have all your fixtures (stubbed responses for your Unit Tests) in your Xcode project linked with your Unit Test target.

Note: You may even put all your fixtures in a custom bundle (let's call it Fixtures.bundle) and then use the helper macros to get it with OHPathForFileInBundle(@"wsresponse.json",OHResourceBundle(@"Fixtures")).

Set request and response time

You can simulate a slow network by setting the requestTime and responseTime of your OHHTTPStubsResponse. This is useful to check that your user interface does not freeze and that you have all your activity indicators working while waiting for responses in bad network conditions.

You may use the commoidty chainable setters responseTime: and requestTime:responseTime: to set those values and easily chain method calls:

[OHHTTPStubs stubRequestsPassingTest:^BOOL(NSURLRequest *request) {
    return [request.URL.host isEqualToString:@"mywebservice.com"];
} withStubResponse:^OHHTTPStubsResponse*(NSURLRequest *request) {
    return [[OHHTTPStubsResponse responseWithJSONObject:someDict statusCode:200 headers:nil]
            requestTime:1.0 responseTime:3.0];
}];

OHHTTPStubs will wait requestTime before sending the NSHTTPURLResponse, and then start sending chunks of the stub data regularly during the period of responseTime, to simulate the slow network.

At the end, you will only have the full content of your stub data after requestTime+responseTime, time after which the completion block or connectionDidFinishLoading: delegate method will be called.

You can specify a network speed instead of a responseTime by using a negative value. See below.

Simulate a down network

You may also return a network error for your stub. For example, you can easily simulate an absence of network connection like this:

[OHHTTPStubsResponse responseWithError:[NSError errorWithDomain:NSURLErrorDomain code:kCFURLErrorNotConnectedToInternet userInfo:nil]];

Advanced Usage

Use macros to build your fixtures path

OHHTTPStubsResponse.h includes a useful set of macros to build a path to your fixtures easily, like OHPathForFileInBundle, OHPathForFileInDocumentsDir and OHResourceBundle. You are encouraged to use them to build your path more easily.

Especially, they use [NSBundle bundleForClass:self.class] to reference your app bundle (and not [NSBundle mainBundle] as one may think), so that they still work with OCUnit and XCTestKit when unit-testing your app in the Simulator.

Using download speed instead of responseTime

When building the OHHTTPStubsResponse object, you can specify a response time (in seconds) so that the sending of the fake response will be spread over time. This allows you to simulate a slow network for example. (see "Set request and response time")

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   =    -7 =    7 KB/s =    56 kbps
OHHTTPStubsDownloadSpeedEDGE   =   -16 =   16 KB/s =   128 kbps
OHHTTPStubsDownloadSpeed3G     =  -400 =  400 KB/s =  3200 kbps
OHHTTPStubsDownloadSpeed3GPlus =  -900 =  900 KB/s =  7200 kbps
OHHTTPStubsDownloadSpeedWifi   = -1500 = 1500 KB/s = 12000 kbps

Example:

return [[OHHTTPStubsResponse responseWithData:nil statusCode:400 headers:nil]
        responseTime:OHHTTPStubsDownloadSpeed3G];

Stack multiple stubs and remove installed stubs

• You can call stubRequestsPassingTest:withStubResponse: multiple times. It will just add the stubs in an internal list of stubs.

This may be useful to install different stubs in various places in your code, or to separate different stubbing conditions more easily. See the OHHTTPStubsDemo project for a typical example.

When a network request is performed by the system, the stubs are called in the reverse order that they have been added, the last added stub having priority over the first added ones. The first stub that returns YES for the first parameter of stubRequestsPassingTest:withStubResponse: is then used to reply to the request.

• You can remove any given stub with the removeStub: method. This method takes as a parameter the id<OHHTTPStubsDescriptor> object returned by stubRequestsPassingTest:withStubResponse: (Note: this returned object is already retained by OHHTTPStubs while the stub is installed, so there is no need to keep a __strong reference to it).
• You can remove the latest added stub with the removeLastStub method.
• You can also remove all stubs at once with the removeAllStubs method.

This last one is useful when using OHHTTPStubs in your Unit Tests, to remove all installed stubs at the end of each of your test case to avoid stubs installed in one test case to be still installed for the next test case.

- (void)tearDown
{
    [OHHTTPStubs removeAllStubs];
}

Name your stubs and log their activation

You can add a name of your choice to your stubs. The only purpose of this is to easily identify your stubs for debugging, like when displaying them in your console.

id<OHHTTPStubsDescriptor> stub = [OHHTTPStubs stubRequestsPassingTest:... withStubResponse:...];
stub.name = @"Stub for text files";

You can even imagine applying the .name = ... affectation directly if you don't need to use the returned id<OHHTTPStubsDescriptor> otherwise:

[OHHTTPStubs stubRequestsPassingTest:^BOOL(NSURLRequest *request) {
   ...
} withStubResponse:^OHHTTPStubsResponse*(NSURLRequest *request) {
   ...
}].name = @"Stub for text files";

You can then list all the installed stubs using [OHHTTPStubs allStubs], which return an array of id<OHHTTPStubsDescriptor> objects so you can display their name on the console. This is useful to check that you didn't forget to remove some previous stubs that are still installed for example.

You can also setup a block to execute each time a request has been stubbed, using onStubActivation: method, typically to log the stub being used for each request:

[OHHTTPStubs onStubActivation:^(NSURLRequest *request, id<OHHTTPStubsDescriptor> stub) {
    NSLog(@"%@ stubbed by %@", request.URL, stub.name);
}];

OHHTTPStubs and NSURLSession

OHHTTPStubs use a custom private NSURLProtocol to intercept its requests.

OHHTTPStubs is automatically enabled by default, both for:

• requests made using NSURLConnection or [NSURLSession sharedSession] (that are based on [NSURLProtocol registerProtocol:] to look for custom protocols for every requests), because this protocol is installed as soon as you use the OHHTTPStubs class (installed in the +initialize method)
• requests made using a NSURLSession created with a NSURLSessionConfiguration and [NSURLSession sessionWithConfiguration:] (thanks to method swizzling that insert the private protocol used by OHHTTPStubs into the protocolClasses of [NSURLSessionConfiguration defaultSessionConfiguration] and [NSURLSessionConfiguration ephemeralSessionConfiguration] automagically)

Note however that OHHTTPStubs can't work on background sessions (sessions created using [NSURLSessionConfiguration backgroundSessionConfiguration]) because background sessions don't allow the use of custom NSURLProtocols. There's nothing we can do about it, sorry.

If you need to disable (and re-enable) OHHTTPStubs globally or per session, you can use:

• [OHHTTPStubs setEnabled:] for NSURLConnection/[NSURLSession sharedSession]-based requests
• [OHHTTPStubs setEnabled:forSessionConfiguration:] for requests sent on a session created using [NSURLSession sessionWithConfiguration:...]

There is generally no need to explicitly call setEnabled: or setEnabled:forSessionConfiguration: using YES as this is the default.

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Installing in your projects

CocoaPods is the easiest way to add third-party libraries like OHHTTPStubs in your projects. Simply add pod 'OHHTTPStubs' to your Podfile and you are done.

Note: OHHTTPStubs needs iOS5 minimum.

Warning: Be careful anyway to include OHHTTPStubs only in your test targets, or only use it in #if DEBUG portions, so that its code is not included in your release for the AppStore !

In case you don't want to use CocoaPods (but you should!!!), the OHHTTPStubs project is provided as a Xcode project that generates a static library, so simply add its xcodeproj to your workspace and link your app against the libOHHTTPStubs.a library. See here for detailed instructions.

About OHHTTPStubs Unit Tests

If you want to be able to run OHHTTPStubs' Unit Tests, be sure you cloned the AFNetworking submodule (by using the --recursive option when cloning your repo, or using git submodule init and git submodule update) as it is used by some of OHHTTPStubs unit tests.

Every contribution to add more unit tests is welcome.

Change Log

The changelog is available here in the dedicated wiki page.

License and Credits

This project and library has been created by Olivier Halligon (@AliSoftware) and is under the MIT License.

It has been inspired by this article from InfiniteLoop.dk. I would also like to thank to @kcharwood for its contribution, and everyone who contributed to this project on GitHub.