A somewhat meta test case for testing whether the specified prefixed classes have matching unit test case classes.

Unit Test Coverage

#import <UIKit/UIKit.h>
#import <XCTest/XCTest.h>
#import <objc/runtime.h>

@interface UnitTestCoverageTests : XCTestCase

@end

@implementation UnitTestCoverageTests

- (void)testClassCoverage {
    
    int numberOfClasses = objc_getClassList(NULL, 0);
    if (numberOfClasses > 0)
    {
        NSString *const prefixForClassThatShouldHaveTest = @"SW";
        NSString *const testClassSuffix = @"Tests";
        
        Class *classes = (__unsafe_unretained Class *)malloc(sizeof(Class) * numberOfClasses);
        numberOfClasses = objc_getClassList(classes, numberOfClasses);
        
        NSMutableArray *classesThatShouldHaveTests = [NSMutableArray array];
        NSMutableArray *testClasses = [NSMutableArray array];
        
        for (unsigned int i = 0; i < numberOfClasses; ++i)
        {
            Class cls = classes[i];
            NSString *className = [NSString stringWithFormat:@"%s", class_getName(cls)];
            if ([className hasPrefix:prefixForClassThatShouldHaveTest])
            {
                // Is this a test case? (Naively based on class name suffix)
                if ([className hasSuffix:testClassSuffix])
                {
                    // Remove the suffix, assuming that the test class
                    // name matches the name of a "real" class
                    NSString *testClassNameWithoutSuffix = [className substringToIndex:className.length - testClassSuffix.length];
                    [testClasses addObject:testClassNameWithoutSuffix];
                }
                else
                {
                    [classesThatShouldHaveTests addObject:className];
                }
            }
        }
        free(classes);
        
        // Remove the classes where a test case was found
        NSMutableArray *classesThatDontHaveTests = [classesThatShouldHaveTests mutableCopy];
        [classesThatDontHaveTests removeObjectsInArray:testClasses];
        
        for (NSString *nameOfClassThatDoesNotHaveTest in classesThatDontHaveTests)
        {
            XCTAssert(0, @"%@ does not have a test case", nameOfClassThatDoesNotHaveTest);
        }
    }
}

@end

Modify the following line to suit your project's class prefix:
NSString *const prefixForClassThatShouldHaveTest = @"SW";

Modify the following line if your test case classes have a different suffix:
NSString *const testClassSuffix = @"Tests";