[Perf] Migrate unswizzle-based unit tests to SPM (#11903)

FirebasePerformance.podspec

@@ -45,9 +45,6 @@ Firebase Performance library to measure performance of Mobile and Web Apps.
 
   preprocessor_definitions = 'FIRPerformance_LIB_VERSION=' + String(s.version)
   preprocessor_definitions += ' PB_FIELD_32BIT=1 PB_NO_PACKED_STRUCTS=1 PB_ENABLE_MALLOC=1'
-  if ENV['FPR_UNSWIZZLE_AVAILABLE'] && ENV['FPR_UNSWIZZLE_AVAILABLE'] == '1' then
-    preprocessor_definitions += ' UNSWIZZLE_AVAILABLE=1'
-  end
 
   s.pod_target_xcconfig = {
     'GCC_PREPROCESSOR_DEFINITIONS' => preprocessor_definitions,

FirebasePerformance/Sources/Instrumentation/FPRSelectorInstrumentor.m

@@ -17,9 +17,8 @@
 #import "FirebasePerformance/Sources/Common/FPRDiagnostics.h"
 
 #import <GoogleUtilities/GULSwizzler.h>
-#ifdef UNSWIZZLE_AVAILABLE
-#import <GoogleUtilities/GULSwizzler+Unswizzle.h>
-#endif
+
+#import <objc/message.h>
 
 @implementation FPRSelectorInstrumentor {
   // The class this instrumentor operates on.
@@ -76,11 +75,15 @@ - (void)swizzle {
 
 - (void)unswizzle {
   _swizzled = NO;
-#ifdef UNSWIZZLE_AVAILABLE
-  [GULSwizzler unswizzleClass:_class selector:_selector isClassSelector:_isClassSelector];
-#else
-  NSAssert(NO, @"Unswizzling is disabled.");
-#endif
+  // Unswizzling is provided by GoogleUtilities' GULSwizzlerTestHelpers category on GULSwizzler,
+  // which is only present at runtime when the hosting target links it (e.g. unit tests).
+  SEL unswizzleSelector = NSSelectorFromString(@"unswizzleClass:selector:isClassSelector:");
+  if ([GULSwizzler respondsToSelector:unswizzleSelector]) {
+    ((void (*)(Class, SEL, Class, SEL, BOOL))objc_msgSend)([GULSwizzler class], unswizzleSelector,
+                                                           _class, _selector, _isClassSelector);
+  } else {
+    NSAssert(NO, @"Unswizzling is disabled.");
+  }
 }
 
 - (IMP)currentIMP {

FirebasePerformance/Tests/Unit/FPRClassInstrumentorTest.m

@@ -57,8 +57,6 @@ - (void)testCannotInstrumentSameSelectorTwice {
 
 #pragma mark - Unswizzle based tests
 
-#if !SWIFT_PACKAGE
-
 /** Tests swizzling an instance selector. */
 - (void)testSwizzleInstanceSelector {
   FPRClassInstrumentor *classInstrumentor =
@@ -158,6 +156,4 @@ - (void)testVoidReturnClassSelector {
   [classInstrumentor unswizzle];
 }
 
-#endif  // SWIFT_PACKAGE
-
 @end

FirebasePerformance/Tests/Unit/FPRInstrumentTest.m

@@ -65,8 +65,6 @@ - (void)testRegisterAlreadyRegisteredClassInstrumentor {
 
 #pragma mark - Unswizzle based tests
 
-#if !SWIFT_PACKAGE
-
 - (void)testDeregisterInstrumentors {
   FPRInstrument *instrument = [[FPRInstrument alloc] init];
   FPRClassInstrumentor *classInstrumentor =
@@ -86,6 +84,4 @@ - (void)testDeregisterInstrumentors {
   [classInstrumentor unswizzle];
 }
 
-#endif  // SWIFT_PACKAGE
-
 @end

FirebasePerformance/Tests/Unit/FPRInstrumentationTest.m

@@ -37,8 +37,6 @@ - (void)testInit {
 
 #pragma mark - Unswizzle based tests
 
-#ifndef SWIFT_PACKAGE
-
 - (void)testRegisterInstrumentGroup {
   FPRInstrumentation *instrumentation = [[FPRInstrumentation alloc] init];
   NSUInteger numberOfInstrumentsInGroup =
@@ -53,6 +51,4 @@ - (void)testDeregisterInstrumentGroup {
   XCTAssertTrue([instrumentation deregisterInstrumentGroup:kFPRInstrumentationGroupNetworkKey]);
 }
 
-#endif  // SWIFT_PACKAGE
-
 @end

FirebasePerformance/Tests/Unit/FPRSelectorInstrumentorTest.m

@@ -57,8 +57,6 @@ - (void)testInitWithSelector {
 
 #pragma mark - Unswizzle based tests
 
-#ifndef SWIFT_PACKAGE
-
 - (void)testInstanceMethodSwizzle {
   NSString *expectedDescription = @"Not the description you expected!";
   FPRSelectorInstrumentor *instrumentor =
@@ -329,8 +327,6 @@ typedef void (^DataTaskCompletionHandler)(NSData *_Nullable, NSURLResponse *_Nul
   }
 }
 
-#endif  // SWIFT_PACKAGE
-
 /** Tests attempting to swizzle non-existent/unimplemented method (like @dynamic) returns nil. */
 - (void)testNonexistentMethodReturnsNil {
   FPRSelectorInstrumentor *instrumentor =

FirebasePerformance/Tests/Unit/Instruments/FPRNSURLConnectionInstrumentTest.m

@@ -14,8 +14,6 @@
 
 #pragma mark - Unswizzle based tests
 
-#if !SWIFT_PACKAGE
-
 #import "FirebasePerformance/Tests/Unit/Instruments/FPRNSURLConnectionInstrumentTestDelegates.h"
 
 #import <XCTest/XCTest.h>
@@ -519,5 +517,3 @@ - (void)testDownloadDelegateCompletionAPIGetsCalledEvenIfDataDelegateIsImplement
 }
 
 @end
-
-#endif  // SWIFT_PACKAGE