BDD-style testing using Objective-C
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BDD-style testing using Objective-C


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  • Don't forget to initialize submodules:

      $ git submodule update --init

Non-iPhone testing

  • Build the Cedar framework. Note that you must build for an Objective-C runtime that supports blocks; this means Mac OS X 10.6, or a runtime from Plausible Labs (see below).

  • Create a command-line executable target for your tests in your project. Name this target Specs, unless you have another name you'd prefer.

  • Add the Cedar framework to your project, and link your Specs target with it.

  • Do the Copy Framework Dance:

    • Add a Copy Files build phase to your Specs target.
    • Select the Frameworks destination for the build phase.
    • Add Cedar to the new build phase.
  • Add a main.m to your Specs target that looks like this:

      #import <Cedar/Cedar.h>
      int main (int argc, const char *argv[]) {
        return runAllSpecs();
  • Write your specs. Cedar provides the SpecHelper.h file with some minimal macros to remove as much distraction as possible from your specs. A spec file need not have a header file, and looks like this:

      #import <Cedar/SpecHelper.h>
      describe(@"Foo", ^{
        it(@"should do something", ^{
  • Build and run. Note that, unlike OCUnit, you must run your executable in order to run your specs. Also unlike OCUnit this allows you to use the debugger when running specs.

iPhone testing

  • Build the Cedar-iPhone static framework. This framework contains a universal binary that will work both on the simulator and the device. NOTE: due to a bug in the build process the script that builds the framework will sometimes not copy all of the header files appropriately. If after you build the Headers directory under the built framework is empty, try deleting the built framework and building again.

  • Create a Cocoa Touch executable target for your tests in your project. Name this target UISpecs, or something similar.

  • Open the Info.plist file for your project and remove the "Main nib file base name" entry. The project template will likely have set this to "MainWindow."

  • Add the Cedar-iPhone static framework to your project, and link your UISpecs target with it.

  • Add -ObjC, -lstdc++ and -all_load to the Other Linker Flags build setting for the UISpecs target. This is necessary for the linker to correctly load symbols for Objective-C classes from static libraries.

  • Add a main.m to your UISpecs target that looks like this:

      #import <UIKit/UIKit.h>
      #import <Cedar-iPhone/Cedar.h>
      int main(int argc, char *argv[]) {
          NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
          int retVal = UIApplicationMain(argc, argv, nil, @"CedarApplicationDelegate");
          [pool release];
          return retVal;
  • Build and run. The simulator (or device) should start and display the status of each of your spec classes in a table view. You can navigate the hierarchy of your examples by clicking on the table cells.

  • If you would like to use OCHamcrest or OCMock in your UI specs, Pivotal has created static frameworks which will work on the iPhone for both. These must be built so you can add them as available frameworks in your specs. See the sections below on Matchers and Mocks for links to the relevant projects.

  • If you would like to run specs both in your UI spec target and your non-UI spec target, you'll need to conditionally include the appropriate Cedar headers in your spec files depending on the target SDK. For example:

      #define HC_SHORTHAND
      #import <Cedar-iPhone/SpecHelper.h>
      #import <OCMock-iPhone/OCMock.h>
      #import <OCHamcrest-iPhone/OCHamcrest.h>
      #import <Cedar/SpecHelper.h>
      #import <OCMock/OCMock.h>
      #import <OCHamcrest/OCHamcrest.h>


Cedar does not provide matchers, but it works with the fine array of matchers provided by the Hamcrest project; you can fetch the Objective-C port from the Hamcrest SVN repo. Build and link the Hamcrest framework by following their instructions, and add the following at the top of your spec files:

#import <OCHamcrest/OCHamcrest.h>

Pivotal also has a fork of a GitHub import of the OCHamcrest codebase. This fork contains our iPhone-specific static framework target.

Shared example groups

Cedar supports shared example groups; you can declare them in one of two ways: either inline with your spec declarations, or separately.

Declaring shared examples inline with your specs is the simplest:


sharedExamplesFor(@"a similarly-behaving thing", ^(NSDictionary *context) {
    it(@"should do something common", ^{

describe(@"Something that shares behavior", ^{
    itShouldBehaveLike(@"a similarly-behaving thing");

describe(@"Something else that shares behavior", ^{
    itShouldBehaveLike(@"a similarly-behaving thing");


Sometimes you'll want to put shared examples in a separate file so you can use them in several specs across different files. You can do this using macros specifically for declaring shared example groups:


sharedExamplesFor(@"a thing with globally common behavior", ^(NSDictionary *context) {
    it(@"should do something really common", ^{


The context dictionary allows you to pass example-specific state into the shared example group. You can populate the context dictionary available on the SpecHelper object, and each shared example group will receive it:

sharedExamplesFor(@"a red thing", ^(NSDictionary *context) {
    it(@"should be red", ^{
        Thing *thing = [context objectForKey:@"thing"];
        assertThat(thing.color, equalTo(red));

describe(@"A fire truck", ^{
        [[SpecHelper specHelper].sharedExampleContext setObject:[FireTruck fireTruck] forKey:@"thing"];
    itShouldBehaveLike(@"a red thing");

describe(@"An apple", ^{
        [[SpecHelper specHelper].sharedExampleContext setObject:[Apple apple] forKey:@"thing"];
    itShouldBehaveLike(@"a red thing");

Previously, you needed to instantiate and pass in your own dictionary, but this led to confusion and unavoidable memory leaks. You should change any code that uses a local context dictionary to use the global shared example context dictionary.

Mocks and stubs

Cedar works fine with OCMock. You can download and use the OCMock framework. Pivotal also has a fork of a GitHub import of the OCMock codebase, which contains our iPhone-specific static framework target.

Pending specs

If you'd like to specify but not implement an example you can do so like this:

      it(@"should do something eventually", PENDING);

The spec runner will not try to run this example, but report it as pending. The PENDING keyword simply references a nil block pointer; if you prefer you can explicitly pass nil as the second parameter. The parameter is necessary because C, and thus Objective-C, doesn't support function parameter overloading or default parameters.


The project root contains a file named MACROS, which contains some useful Xcode macros for writing Cedar specs. To load the macros copy the contents of the file into this file:

    ~/Library/Application\ Support/Developer/Shared/Xcode/Specifications/ObjectiveC.xctxtmacro

You may need to create that file. If the file already exists, and contains pre- existing macros, be careful to insert the Cedar macros inside the existing parentheses properly.

To use the macros, type the shortcut string, followed by Ctrl-. or Ctrl-, As an example, typing 'cdesc' followed by Ctrl-. will expand to:

    describe(@"<#!subject under test!#>", ^{

But I'm writing a pre-4.0 iPhone app!

Unfortunately, Apple has made Objective-C blocks, upon which Cedar depends, only available in the Mac OS X 10.6 and iOS 4 runtime. This means if you're not building on a Snow Leopard machine and targeting the desktop runtime or targeting a device or simulator that is running less than iOS 4 then anything using blocks will fail to compile. There are a couple ways around this:

  • Plausible Labs provides patched versions of the GCC compiler and runtime for Leopard and iPhone OS. This link has instructions for installing this compiler and framework. I wrote most of Cedar on a Leopard machine with the 10.5 PLBlocks runtime.

  • Split your project into OS-dependent and OS-independent targets. Domain models and business logic shouldn't (theoretically) depend on the available UI frameworks. Test everything that doesn't require UIKit/CoreGraphics/etc. using Cedar; test the UI using something else.

  • We're open to suggestions.

The Cedar-iPhone target builds a framework specifically designed for specs on the iPhone device. It includes a static library that includes builds targeting both the simulator and device runtimes.

We've created a sample iPhone application that runs Cedar specs both on and off the device. You can check it out here.

See the Pivotal forks of OCHamcrest and OCMock on GitHub for iPhone-specific static framework targets.

Contributions and feedback

Welcomed! Feel free to join and contribute to the public Tracker project here.

The public Google group for Cedar is Or, you can follow the growth of Cedar on Twitter: @cedarbdd.

Copyright (c) 2010 Pivotal Labs. This software is licensed under the MIT License.