Fix loading of test resources

Building and testing the project via Xcode copies the resources into
the testing bundle, which is not the case for SwiftPM. Hence the helper
method, that tries loading the resource from the bundle first. If it is
nil then the resource is loaded from the test module path directly.

Tests/HTMLKitTests/HTMLKitParserPerformance.m

@@ -8,6 +8,7 @@
 
 #import <XCTest/XCTest.h>
 #import "HTMLParser.h"
+#import "HTMLKitTestUtil.h"
 
 @interface HTMLKitParserPerformance : XCTestCase
 
@@ -19,9 +20,7 @@
 
 - (void)testParserPerformance
 {
-	NSString *path = [[NSBundle bundleForClass:self.class] resourcePath];
-	path = [path stringByAppendingPathComponent:@"Fixtures"];
-	path = [path stringByAppendingPathComponent:@"HTML Standard.html"];
+	NSString *path = [HTMLKitTestUtil pathForFixture:@"HTML Standard" ofType:@"html" inDirectory:@"Fixtures"];
 
 	NSString *string = [NSString stringWithContentsOfFile:path encoding:NSUTF8StringEncoding error:nil];