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Technical Q&A QA1954

Cannot load underlying module for XCTest

Q: My Xcode project fails compiling with a "Cannot load underlying module for XCTest" error message. How do I resolve this issue?

A: You may be getting this error for any of the following reasons:

Your test class was added to a target, which is not a test target.
Test classes, which are XCTestCase subclasses and contain UI testing or unit testing methods, should only be added to test targets. Remove these classes from any target in your Xcode project that is not a test target in order to resolve your issue as shown in Figure 2.

Figure 1 Xcode fails compiling: The CalcUITests class is a member of both the target being tested (Calc) and UI test target (CalcUITests).

Figure 1 Xcode fails compiling: The CalcUITests class is a member of both the target being tested (Calc) and UI test target (CalcUITests).

Figure 2 Xcode successfully builds: The CalcUITests class is a member of the CalcUITests UI test target.

Figure 2 Xcode successfully builds: The CalcUITests class is a member of the CalcUITests UI test target.

The XCTest framework was imported into a source file, which is not a test class.
Remove import XCTest from any source file that is not a test class in your project in order to resolve your issue as shown in Figure 4.

Figure 3 Xcode fails compiling: Calculator, a class from the CalculatorKit framework, imports the XCTest framework.

Figure 3 Xcode fails compiling: Calculator, a class from the CalculatorKit framework, imports the XCTest framework.

Figure 4 Xcode successfully builds: The Calculator no longer imports the XCTest framework.

Figure 4 Xcode successfully builds: The Calculator no longer imports the XCTest framework.

Document Revision History

Date	Notes
2017-10-25	New document that describes how to resolve the "Cannot load underlying module for XCTest" error message.

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