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How to enable Xcode Code Coverage?

By Hamid Akhtar, Community Contributor -

Table of Contents

How can you tell the difference between good and bad code? In most cases, tests will reveal the solution. Software testing, both during and after the production cycle, is crucial for finding and fixing bugs in the final product. Using efficient code coverage techniques is a crucial instrument for error and bug discovery.

Importance of Code Coverage in Software Development

The word “test coverage” refers to a method used to ascertain whether or not our test cases adequately cover the application code and how much of the code is exercised during test execution. 

  • With 10 criteria and 100 tests, 90% test coverage is achieved if 90% of the tests are actually run. 
  • The leftover tests can now have more test cases developed based on this metric. 

Enabling Xcode code coverage  is a huge win. You’ll love how coders are liberated from having to use external tools, and seeing that functionality baked right into the source code editor is icing on the cake.

Overview of Xcode

All Apple users have free access to Xcode, Apple’s IDE for creating apps for all of Apple’s platforms.

  • Apps can be designed, developed, and published for every Apple device with the help of Xcode. 
  • This includes iOS, iPadOS, tvOS, watchOS, and macOS. Swift, Objective-C, Objective-C++, C, C++, Java, Python, and many more have all been ported to Xcode’s source code support.
  • Only Xcode is authorized for use in developing and distributing applications through the Apple App Store. 
  • The latest version of Xcode (Xcode 14.0.1) is optimized for performance and simplicity, letting devs build cross-platform apps with Swift and SwiftUI.

Note: BrowserStack  integrates with popular iOS testing frameworks XCTest and XCUITest, which support XCode. As a result, they ensure a bug-free app experience for their users.

Test on BrowserStack

How to measure Xcode Test Coverage?

Because it is a quantitative study, measuring code coverage is straightforward. To determine how much of a program module has been tested, follow these steps:

  • Percentage of Code Coverage (in%) equals (Lines of Tested Code / Total Lines of Code in the Relative Software Component) * 100
  • Take the case of evaluating a 1000-line software component. If 800 lines of code are verified, then 80% of the code component has been tested.
  • If that’s the case, you may be pondering what it would take to achieve full code coverage.

A simple metric to include in your initiatives is code coverage: The number of lines of our code that were executed is counted by Xcode after it starts and runs all of your tests. 

  • To test code coverage in action, make a new iOS app using the Single View App template, name it Coverage, and make sure the “Include Unit Tests” checkbox is selected.
  • You will start by turning on code coverage monitoring in Xcode since it is off by default. So select Scheme > Edit Scheme from the Product menu. Then select the Test scheme and open the Options page. For Xcode to collect code coverage information while your tests are running, lastly, select the Code Coverage box.
  • You have a lot of method stubs to work with thanks to Xcode’s template. 
  • So, in your new project, make a new Swift file named User.swift and fill it with this code:
struct User {
var username: String
var password: String

init(username: String, password: String) {
self.username = username
self.password = String(password.reversed())
}

func authenticate() -> Bool {
if username.count > 5 && password.count >= 12 {
return true
} else {
return false
}
}
}
  • Now, open CoverageTests.swift and add the following test method:
func testUserAuthenticationSucceeds() {

// given

let user = User(username: "twostraws", password: "i_heart_chris_lattner")




// when

let result = user.authenticate()




// then

XCTAssertTrue(result, "User authentication should succeed.")

}
  • Finally, hit Cmd+U to execute all of our tests while tracking code coverage. This is a good illustration to use when learning about code coverage because it highlights three crucial points.
  • To find “Coverage” under the most current test run, launch the report navigator by pressing Cmd+9 on your keyboard. This will display the statistics on code coverage that was recently gathered; open the disclosure indicators to view User.swift. 

Three points ought to be evident:

  • The initializer for User and its properties is essentially an unnamed function (the green “F” with nothing next to it). You initialize a User before calling authenticate(), so even though it isn’t being tested explicitly, it is still marked as having 100% code coverage.
  • Given that the call to authenticate() only has 5 lines of code, including brackets, it has a rather odd coverage percentage of 57.1%.
  • A third line reads, “implicit closure #1: @autoclosure () throws -> Swift.Bool in Coverage.User.authenticate……..” This should have 100% coverage.

Enabling XCode Code Coverage

Since Xcode 7, you can use its built-in features to create code coverage. Unfortunately, it’s not turned on by default. Because of this, you may be unaware of it. 

This piece will demonstrate how straightforward it is to enable code coverage in your project and will highlight the benefits you’ll reap as a result.

1. Setting up a Test Target

Configuring build settings for code coverage

  • By tapping the active scheme on the toolbar, you can display the scheme editor window.
  • Then choose “Edit Scheme…” from the menu options of the scheme editor.
  • From the left pane, choose the Test option.
  • To gather coverage information, enable the Code Coverage checkbox.
  • That’s it; the code coverage option will now be active.

2. Running tests with Code Coverage in Xcode

In Xcode 5 or later, a test target is preconfigured for all new apps, frameworks, and library applications. A test bundle, a test class, and a template test method are displayed when you open the test navigator when you first initiate a new project. 

However, you may be opening an older file from Xcode that doesn’t yet have test targets set up. The workflow described here takes into account a current project without any tests.

  • When you open the test navigator, select New Unit Test Target from the Add button (+) in the lower left.

open the test navigator, select New Unit Test Target

  • In the following window, select either the macOS or iOS Unit Testing Bundle, and then press Next. 
  • Change the Product Name and other settings to suit your requirements in the new target setup assistant that has opened.

Change the Product Name in new target setup assistant

  • Click Finish to add your target to the test navigator view. This target comprises a template test class and two test method templates.

3. Viewing Xcode test coverage report

Now that testing has been added to your project, you must create tests that accomplish something beneficial.

  • But first, in the test navigator, hover over the SampleCalcTests test class and select the Run button to execute all of the class’s test methods.
  •  Green checkmarks next to the function names and in the source editor gutter denote the result.

Xcode test coverage report

4. Code Coverage Reporting

Because the template unit and performance tests are both empty, they report success; no failure was claimed. I

In the figure, look for the grey diamond on line 34, which represents the measureBlock: method. When you click this diamond, the Performance Result panel appears.

Code Coverage Reporting

Tips for optimizing Code Coverage in Xcode

1. Writing effective unit tests

  • You have the choice to select Include Tests whenever you start a new project. These comprise both UI tests and unit tests.
  • You can also include a Unit Testing Bundle in an existing project. Activate File > New > Target.
  • Before running a test method, the setUp() instance method is always called. To include your version, you override it. 
  • Override the setUp() class method instead if you want to execute the initial code in a test class once.

2. Targeting untested code

  • Xcode provides a file- and method-level breakdown of the coverage result(data). 
  • By selecting a specific function, you can examine its source code and learn which lines of code are not being tested. 
  • You can see the frequency with which each branch was used in the test in the right-hand gutter. 
  • Branches that were never run are highlighted in red, allowing you to quickly locate the untested code and fill in the gaps with new tests.

Targeting untested code

3. Minimizing false positives in code coverage results

Running a test that is effective results in false positives. However, the test’s result reveals a misstep.

  • Any testing environment needs to reduce false positives to function properly! You must thoroughly check both the initial and end conditions for flawless automated testing. 
  • To ensure “sound” output, a test case tries to perform a specific set of processes with a specific set of input data. Therefore, the test should behave as it should if you want to see positive results when they are truly positive. 
  • It is essential to check that the test begins where it should have and that there is no deviation from the input’s predetermined state.

Troubleshooting Common Issues with Xcode Code Coverage Report

1. Missing code coverage data

  • The navigator is located on the left side of Xcode. To access it, first, enable code coverage support (edit scheme -> test -> options -> select code coverage box). 
  • You will notice several symbols at the top. select the final one on the right. (it looks like a message bubble). 
  • Within that tab, you will see all the tests you ran. Within each test is a “coverage” item. Click on one of those to get the coverage report for that specific test.

2. Discrepancies between code coverage results and expected coverage

  • The question of whether to prioritize code or test coverage and why, must be addressed now. It would be illogical to pick one over the other given that they are two distinct methods of assessment.
  •  White-box testing is more closely associated with the quantifiable measure of code coverage. Test coverage, on the other hand, is an intuitive metric and a black-box method of testing. 
  • Which method is better, code coverage or test coverage? depends on your specific company’s needs and the complexity of the software being tested. However, test coverage and code coverage are used together in most situations.

3. Problems with test target configuration

  • You can modify the build parameters for one target or every target in your project thanks to the high degree of configurability of the Xcode build process. 
  • Every step of the build process is governed by the build options, including how Xcode links your executable, compiles your source code, produces debugging information, and packages and spreads your code. 
  • To enable the tools and steps involved in the build process, Xcode has hundreds of build settings.

Continuous Testing and Code Coverage

Continuous delivery includes software testing strategies like code coverage.. 

  • When evaluating the integrity of a program or application’s source code, continuous delivery relies on a collection of automated tests (also known as test suites). 
  • Even though these automated tests help determine the build’s quality, they aren’t always accurate. 
  • Even if a build succeeds, how much of its source code runs cannot be determined by automatic tests alone. Where code coverage comes in is at this point.

FAQs

1. How do I see code coverage in Xcode?

  • LLVM supports the Xcode testing option for code coverage. 
  • When code coverage is enabled, LLVM instruments the code and collects coverage information based on how frequently methods and functions are called. 
  • Whether they are unit tests or user interface tests, the code coverage option can gather data to report on tests of correctness and speed.
  • From the scheme editor option, choose Edit Scheme.
  • Choose the Test option.
  • For gathering coverage information, turn on the Code Coverage option.

2. How do I check my test coverage percentage in Xcode?

  • Activate the tests and go to the Test navigator
  • Jump to Report is available by performing a right-click on the test.
  • You should see “Test” next to your destination. Right-click it and choose “Coverage.”
  • The information about test coverage is then displayed.

3. How do I get Xcode unit test code coverage?

  • The proportion of code that has been subjected to the automated unit or functional tests is  “code coverage.”
  • You can configure Xcode to use Apple’s LLVM code compiler to produce the necessary code coverage files. 
  • One option generates reports in XML/HTML format, while the other enables the visualization of reports directly within Xcode.

Closing Notes

You can use code coverage to find the solutions to the following questions right now.

  • If you perform your tests, what exactly is the code that is executed?
  • Where in your code is there a gap in testing?

To guarantee that every portion of your code is executed, code coverage is an invaluable tool. It provides an approximation of the remaining task. But don’t equate that with how well your tests perform or the quality of your tests. 

Code coverage only reveals how much of the code has actually been executed. There is no deeper significance to it. Completely useless tests can be written with 100% code coverage. Make sure that you fully grasp that before turning on the choice. Do not rely on code coverage as an indicator of test quality.

Consider  BrowserStack App automate to perform your UI tests in a fully automated environment. Access a variety of flagship or legacy Apple devices that you can use to execute automation scripts. Although Xcode allows for testing on any type of device using simulated test environments, actual devices are always preferable for the best results.

As BrowserStack provides parallel testing for accelerated CI/CD pipelines and on-demand resource allocation for your expanding requirements, it is a scale-friendly method of testing.

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