Unit testing is invaluable in helping us to identify problems early in the development cycle, both in terms of the implementation and the specification. It also facilitates change, providing confidence that any future changes to the tested code won’t break its expected behavior.
Unit tests are crucial for our project. They help us identify problems early in development. After we have our tests, we need to make sure our test scenarios cover much of our code. Apple defines code coverage as follows:
<a href="https://developer.apple.com/library/archive/documentation/DeveloperTools/Conceptual/testing_with_xcode/chapters/07-code_coverage.html">https://developer.apple.com/library/archive/documentation/DeveloperTools/Conceptual/testing_with_xcode/chapters/07-code_coverage.html</a>
Code coverage is a feature in Xcode that enables you to visualize and measure how much of your code is being exercised by tests. With it, you can determine whether your tests are doing the job you intended.
Although Xcode shows the test coverage nicely, it is hard to visualize and export those results to a human-readable format. Meet Slather. It helps you to convert your test results to different formats such as JSON, HTML, corbura, etc.
<h3>Installing Slather</h3>
<pre><code class="language-bash">[sudo] gem install slather</code></pre>
<h3>Example</h3>
Let&#8217;s learn the usage of Slather by using an example project. We will create a basic SwiftUI application with a single SwiftPM package called FizzBuzzKit. This framework solves the famous <a href="https://en.wikipedia.org/wiki/Fizz_buzz">FizzBuzz</a> problem.
The algorithm is defined as below:
Print integers 1 to N, but print &#8216;Fizz&#8217; if an integer is divisible by 3, &#8216;Buzz&#8217; if an integer is divisible by 5, and &#8216;FizzBuzz&#8217; if an integer is divisible by both 3 and 5.
We will create somehow over-engineered FizzBuzzKit. It will print a string according to the given rules. You can see the source code of the class from here
<a href="https://github.com/appcircleio/appcircle-sample-slather/blob/main/FizzBuzzKit/Sources/FizzBuzzKit/FizzBuzzKit.swift">https://github.com/appcircleio/appcircle-sample-slather/blob/main/FizzBuzzKit/Sources/FizzBuzzKit/FizzBuzzKit.swift</a>
We will write unit tests for FizzBuzzKit. Our tests will cover below scenarios
<ul>
<li>Default initializer should have default values for Fizz and Buzz</li>
<li>It should return correct values for given numbers</li>
<li>Class could be initialized with different numbers and strings</li>
<li>Class could be initialized with filter functions besides numbers</li>
</ul>
It is better to write tests for all those scenarios and check if our code is working for every path.
If you switch your scheme to &#8216;FizzBuzzKit&#8217; and hit ⌘U you can see the test results. It all passes.
Our test covers all the mentioned scenarios. To be sure that our test covers all the code we&#8217;ve written we will check our test coverage.
Here are the steps to use Slather with Xcode and enabling it on our Appcircle workflow:
1. Enable Test Coverage
We need to enable test coverage in our project to get test coverage results. First, make sure your project has the following settings enabled.:
<img class="alignnone size-full wp-image-2480" src="https://ac.appcircle.io/wp-content/uploads/2022/01/slather-enable-coverage.png" alt="" width="2430" height="1232" srcset="https://ac.appcircle.io/wp-content/uploads/2022/01/slather-enable-coverage.png 2430w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-enable-coverage-300x152.png 300w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-enable-coverage-1030x522.png 1030w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-enable-coverage-768x389.png 768w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-enable-coverage-1536x779.png 1536w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-enable-coverage-2048x1038.png 2048w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-enable-coverage-1500x760.png 1500w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-enable-coverage-705x357.png 705w" sizes="(max-width: 2430px) 100vw, 2430px" />
If we run our tests again, and click Coverage button we can see the coverage of our tests.
<img class="alignnone size-full wp-image-2481" src="https://ac.appcircle.io/wp-content/uploads/2022/01/slather-xcode-test-result.png" alt="" width="856" height="396" srcset="https://ac.appcircle.io/wp-content/uploads/2022/01/slather-xcode-test-result.png 856w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-xcode-test-result-300x139.png 300w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-xcode-test-result-768x355.png 768w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-xcode-test-result-705x326.png 705w" sizes="(max-width: 856px) 100vw, 856px" />
Coverage results can only be seen on Xcode. To get a human-readable format, we need to use an external tool.
Slather can convert Xcode test results to different formats.
2. Run Slather for Xcode
Go to the project directory open your terminal and run the below command
<pre><code class="language-bash">slather coverage --html --scheme FizzBuzzKit Appcircle.xcodeproj</code></pre>
If you are using workspaces or configs, you can change the command line parameters according to the <a href="https://github.com/SlatherOrg/slather">Slather&#8217;s documentation.</a>
You&#8217;ll get a report something like below. If you get an error, try cleaning your DerivedData folder.
<img class="alignnone size-full wp-image-2474" src="https://ac.appcircle.io/wp-content/uploads/2022/01/slather-html-report.png" alt="" width="2416" height="1000" srcset="https://ac.appcircle.io/wp-content/uploads/2022/01/slather-html-report.png 2416w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-html-report-300x124.png 300w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-html-report-1030x426.png 1030w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-html-report-768x318.png 768w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-html-report-1536x636.png 1536w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-html-report-2048x848.png 2048w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-html-report-1500x621.png 1500w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-html-report-705x292.png 705w" sizes="(max-width: 2416px) 100vw, 2416px" />
We can click on each file, and see how our test codes were run and how many times they were invoked.
<img class="alignnone size-full wp-image-2483" src="https://ac.appcircle.io/wp-content/uploads/2022/01/slather-html-detail.png" alt="" width="2376" height="916" srcset="https://ac.appcircle.io/wp-content/uploads/2022/01/slather-html-detail.png 2376w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-html-detail-300x116.png 300w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-html-detail-1030x397.png 1030w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-html-detail-768x296.png 768w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-html-detail-1536x592.png 1536w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-html-detail-2048x790.png 2048w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-html-detail-1500x578.png 1500w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-html-detail-705x272.png 705w" sizes="(max-width: 2376px) 100vw, 2376px" />
Let&#8217;s add this project to <a href="https://appcircle.io/start">Appcircle</a> and see how easy to get test coverage results for our project.
3. Create a new build profile
Create a new build profile and add our repo. You can either use its public link, or you can fork to your account and add it from there.
<img class="alignnone size-full wp-image-2479" src="https://ac.appcircle.io/wp-content/uploads/2022/01/slather-add-buildprofile.png" alt="" width="1500" height="1218" srcset="https://ac.appcircle.io/wp-content/uploads/2022/01/slather-add-buildprofile.png 1500w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-add-buildprofile-300x244.png 300w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-add-buildprofile-1030x836.png 1030w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-add-buildprofile-768x624.png 768w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-add-buildprofile-705x572.png 705w" sizes="(max-width: 1500px) 100vw, 1500px" />
&nbsp;
<img class="alignnone size-full wp-image-2478" src="https://ac.appcircle.io/wp-content/uploads/2022/01/slather-select-repo.png" alt="" width="1426" height="1306" srcset="https://ac.appcircle.io/wp-content/uploads/2022/01/slather-select-repo.png 1426w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-select-repo-300x275.png 300w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-select-repo-1030x943.png 1030w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-select-repo-768x703.png 768w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-select-repo-705x646.png 705w" sizes="(max-width: 1426px) 100vw, 1426px" />
4. Configure your build profile
Go to the config section and fill in the details like below and hit Save.
<img class="alignnone size-full wp-image-2477" src="https://ac.appcircle.io/wp-content/uploads/2022/01/slather-xcode-config.png" alt="" width="1290" height="1510" srcset="https://ac.appcircle.io/wp-content/uploads/2022/01/slather-xcode-config.png 1290w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-xcode-config-256x300.png 256w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-xcode-config-880x1030.png 880w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-xcode-config-768x899.png 768w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-xcode-config-1281x1500.png 1281w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-xcode-config-602x705.png 602w" sizes="(max-width: 1290px) 100vw, 1290px" />
5. Edit your workflow
Edit your workflow and add Slather after the Xcode Unit Test.
<img class="alignnone size-full wp-image-2482" src="https://ac.appcircle.io/wp-content/uploads/2022/01/slather-step.png" alt="" width="1324" height="1512" srcset="https://ac.appcircle.io/wp-content/uploads/2022/01/slather-step.png 1324w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-step-263x300.png 263w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-step-902x1030.png 902w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-step-768x877.png 768w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-step-1313x1500.png 1313w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-step-617x705.png 617w" sizes="(max-width: 1324px) 100vw, 1324px" />
6. Modify your test step
Go to your Xcodebuild for Unit and UI Tests step detail and change it like below:
<img class="alignnone size-full wp-image-2476" src="https://ac.appcircle.io/wp-content/uploads/2022/01/slather-xcodetest-config.png" alt="" width="1290" height="1512" srcset="https://ac.appcircle.io/wp-content/uploads/2022/01/slather-xcodetest-config.png 1290w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-xcodetest-config-256x300.png 256w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-xcodetest-config-879x1030.png 879w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-xcodetest-config-768x900.png 768w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-xcodetest-config-1280x1500.png 1280w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-xcodetest-config-601x705.png 601w" sizes="(max-width: 1290px) 100vw, 1290px" />
7. Edit your Slather Step
Finally, edit your Slather Step and change the configuration accordingly:
<img class="alignnone size-full wp-image-2475" src="https://ac.appcircle.io/wp-content/uploads/2022/01/slather-slatherstep-config.png" alt="" width="1290" height="1504" srcset="https://ac.appcircle.io/wp-content/uploads/2022/01/slather-slatherstep-config.png 1290w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-slatherstep-config-257x300.png 257w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-slatherstep-config-883x1030.png 883w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-slatherstep-config-768x895.png 768w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-slatherstep-config-1287x1500.png 1287w, https://ac.appcircle.io/wp-content/uploads/2022/01/slather-slatherstep-config-605x705.png 605w" sizes="(max-width: 1290px) 100vw, 1290px" />
Hit the Build button. After the build is finished, tap the &#8220;Download Artifacts&#8221; button and easily download Slather coverage results.

Human Readable Xcode Test Results with Slather

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