Saturday, August 17, 2013

Improving the testability of the Nix iOS build facilities

In the previous blog post, I have described some new features of the Nix Android build environment. Apart from Android, the Nix iOS build environment has a few improvements as well, which are mostly related to testing.

Simulating multiple iOS versions

In the previous blog post about the Nix iOS build function, I have described how to install various iPhone simulator SDK versions by picking the preferences option from the 'Xcode' menu bar and selecting the 'Downloads' tab in the window, as shown in the screenshot below:

However, I did not implement any facilities in the simulator function that take these SDK versions into account yet.

Picking a specific SDK version can be done quite easily, by providing the -currentSDKRoot parameter to the iPhone simulator, such as:

$ "iPhone Simulator" -SimulateApplication build/HelloWorld \
  -SimulateDevice 'iPhone' -currentSDKRoot \

In the above case, we have configured the simulator to use the iPhone simulator 6.1 SDK. By changing this parameter, we can use a different version, such as version 5.1.

I have encapsulated the above command-line invocation in the xccodeenv.simulateApp {} Nix function and the paths to the iPhone simulator SDKs in the xcodewrapper. The SDK version can be configured by providing the sdkVersion parameter (which defaults to 6.1):

{xcodeenv, helloworld, device}:

xcodeenv.simulateApp {
  name = "HelloWorld";
  app = helloworld;
  inherit device;
  sdkVersion = "6.1";

This parameter makes it possible to spawn a simulator instance running a specific iOS version.

The described facilities earlier are only for simulating apps. To build an app for a specific iOS revision, the iOS target version must be changed inside the Xcode project settings.

Building signed Apps for release

Apart from the simulator, we may also want to deploy apps to real devices, such as an iPhone, iPad or iPod, either directly or through the App store. In order to do that, we require permission from Apple by signing the apps that we have just built.

As described in the previous blog post, we require a certificate that contains a developer's or company's identity and a mobile provisioning file describing which (groups of) apps of a certain company/developer can be run of which (groups of) devices. These files must be obtained through Apple's Dev Center.

Because of these restrictions, it's hard to test the trivial "Hello World" example case I have developed in the previous blog post on a real device, since it contains a dummy app and company name.

To alleviate these problems, I have created a script that "renames" the example app into a different app, so that an existing developer or company certificate and a mobile provisioning profile of a different app can be used.

By setting the rename parameter to true when calling the composition expression of the example case, we can automatically generate jobs building IPAs and xcarchives for the "renamed" app:

import ./nix-xcodeenvtests/deployment {
  rename = true;
  newName = "MyVeryCoolApp";
  newId = "coolapp";
  newCompanyName = "My Cool Company";
  newDomain = "com.coolcompany";
  ipaCertificateFile = ./adhoc.p12;
  ipaCodeSignIdentity = "iPhone Distribution: My Cool Company";
  ipaCertificatePassword = "";
  ipaProvisioningProfile = ./adhoc.mobileprovision;
  xcArchiveCertificateFile = ./distribution.p12;
  xcArchiveCodeSignIdentity = "iPhone Distribution: My Cool Company";
  xcArchiveCertificatePassword = "";
  xcArchiveProvisioningProfile = ./distribution.mobileprovision;

In the above expression, we changed the name of the app into: "MyVeryCoolApp" and the company name into: "My Cool Company". Moreover, we provide a certificate and mobile provisioning file for the IPA job (which can be deployed to a device directly) and the xcarchive job (which can be used to deploy to the App store).

By running the following command-line instruction:

$ nix-build -A renamedPkgs.testapp_ipa

We can build an IPA allowing us to deploy the test app on a real device. Of course, to do this yourself, the company name and app names should correspond to the ones defined in your certificate and mobile provisioning profile.

Moreover, as with the Android environment in the previous blog post, we can also use Hydra to provide parameters to the composition expression and to retrieve all the resulting artifacts:


In this blog post, I have described some improvements to the Nix iOS facilities. We are now also capable of configuring the SDK versions for the iPhone simulator, and we can build the trivial testcase to run on a real device in addition to the simulator. This is useful for testing the Nix iOS build function.

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