Build error message

Ld /Users/Peter/Library/Developer/Xcode/DerivedData/SearchBox-dpxojbceltozthdhaniikkmuimvy/Build/Products/Debug-iphonesimulator/SearchBoxTests.xctest/SearchBoxTests normal x86_64
    cd /Users/Peter/Developer/iOS/SearchBox
    export IPHONEOS_DEPLOYMENT_TARGET=8.0
    export PATH="/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/usr/bin:/usr/local/opt/rbenv/shims:/Applications/Xcode.app/Contents/Developer/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin"
    /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang -arch x86_64 -bundle -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator8.0.sdk -L/Users/Peter/Library/Developer/Xcode/DerivedData/SearchBox-dpxojbceltozthdhaniikkmuimvy/Build/Products/Debug-iphonesimulator -F/Users/Peter/Library/Developer/Xcode/DerivedData/SearchBox-dpxojbceltozthdhaniikkmuimvy/Build/Products/Debug-iphonesimulator -F/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator8.0.sdk/Developer/Library/Frameworks -F/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/Library/Frameworks -F/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator8.0.sdk/Developer/Library/Frameworks -filelist /Users/Peter/Library/Developer/Xcode/DerivedData/SearchBox-dpxojbceltozthdhaniikkmuimvy/Build/Intermediates/SearchBox.build/Debug-iphonesimulator/SearchBoxTests.build/Objects-normal/x86_64/SearchBoxTests.LinkFileList -Xlinker -rpath -Xlinker @executable_path/Frameworks -Xlinker -rpath -Xlinker @loader_path/Frameworks -Xlinker -objc_abi_version -Xlinker 2 -framework XCTest -fobjc-arc -fobjc-link-runtime -Xlinker -no_implicit_dylibs -mios-simulator-version-min=8.0 -Xlinker -dependency_info -Xlinker /Users/Peter/Library/Developer/Xcode/DerivedData/SearchBox-dpxojbceltozthdhaniikkmuimvy/Build/Intermediates/SearchBox.build/Debug-iphonesimulator/SearchBoxTests.build/Objects-normal/x86_64/SearchBoxTests_dependency_info.dat -o /Users/Peter/Library/Developer/Xcode/DerivedData/SearchBox-dpxojbceltozthdhaniikkmuimvy/Build/Products/Debug-iphonesimulator/SearchBoxTests.xctest/SearchBoxTests

Undefined symbols for architecture x86_64:
  "_OBJC_CLASS_$_SearchService", referenced from:
      objc-class-ref in SearchBoxTests.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

SearchBoxTests.h

//
//  SearchBoxTests.m
//  SearchBoxTests
//
//  Created by Pedro Remedios on 07/10/14.
//  Copyright (c) 2014 Pedro Remedios. All rights reserved.
//

#import <UIKit/UIKit.h>
#import <XCTest/XCTest.h>
#import "SearchService.h"

@interface SearchBoxTests : XCTestCase

@property (nonatomic, strong) SearchService *searchService;

@end

@implementation SearchBoxTests

- (void)setUp {
    self.searchService = [[SearchService alloc] init];
}

- (void)testSearchService {
    
}

@end