Refactor: Add Objective-C unit tests for RemoteConfig public API.

This commit refactors the Objective-C unit tests for the public API of RemoteConfig to align with user feedback.
The changes include:
- Removal of the setUp method.
- Removal of internal instances.
- Group common test functions in single methods.
- Usage of only public APIs.
- Add test for all enums, typedefs and constants.

The tests now cover various methods, properties, enums and typedefs of the RemoteConfig class, verifying their existence by only calling them without any assertion.
No heavy implementations were added, since this is only for API verification.

FirebaseRemoteConfig/Tests/Unit/FIRRemoteConfigTests.m

@@ -0,0 +1,218 @@
+#import <XCTest/XCTest.h>
+
+#import "FirebaseRemoteConfig/Sources/Public/FirebaseRemoteConfig/FIRRemoteConfig.h"
+#import "FirebaseCore/Sources/Public/FirebaseCore/FIRApp.h"
+@import FirebaseABTesting;
+
+@interface FIRRemoteConfigTests : XCTestCase
+@property (nonatomic, strong) FIRApp *mockApp;
+@property (nonatomic, strong) FIRRemoteConfig *remoteConfig;
+@end
+
+@implementation FIRRemoteConfigTests
+
+- (void)setUp {
+    self.mockApp = OCMClassMock([FIRApp class]);
+    OCMStub([self.mockApp isDefaultAppConfigured]).andReturn(YES);
+    self.remoteConfig = [FIRRemoteConfig remoteConfigWithApp:self.mockApp];
+}
+- (FIROptions *)firstAppOptions {
+    FIROptions *options = [[FIROptions alloc] initWithGoogleAppID:@"1:123:ios:123abc"
+                                                    GCMSenderID:@"123"];
+    options.APIKey = @"AIzaSy-ApiKeyWithValidFormat_0123456789";
+    options.projectID = @"project-id";
+    return options;
+}
+
+- (void)testPublicAPI {
+    [FIRRemoteConfig remoteConfig];
+    [FIRRemoteConfig remoteConfigWithApp:self.mockApp];
+    [FIRRemoteConfig remoteConfigWithFIRNamespace:@"namespace"];
+    [FIRRemoteConfig remoteConfigWithFIRNamespace:@"namespace" app:self.mockApp];
+    
+    [self testAllMethods];
+}
+
+- (void)testAllMethods{
+    FIRRemoteConfig *config = [FIRRemoteConfig remoteConfig];
+    FIRRemoteConfigSettings *settings = [[FIRRemoteConfigSettings alloc] init];
+    config.configSettings = settings;
+    
+    [config fetchWithCompletionHandler:^(FIRRemoteConfigFetchStatus status, NSError * _Nullable error) {}];
+    [config fetchWithExpirationDuration:43200 completionHandler:nil];
+    [config fetchAndActivateWithCompletionHandler:^(FIRRemoteConfigFetchAndActivateStatus status, NSError * _Nullable error) {}];
+    [config activateWithCompletion:^(BOOL changed, NSError *_Nullable error){
+      }];
+    
+    FIRRemoteConfigValue *value = config[@"key"];
+    __unused NSString *strValue = value.stringValue;
+    __unused NSNumber *numValue = value.numberValue;
+    __unused NSData *dataValue = value.dataValue;
+    __unused BOOL boolValue = value.boolValue;
+    __unused id jsonValue = value.JSONValue;
+
+    FIRRemoteConfigValue *sourceValue = [config configValueForKey:@"key" source:FIRRemoteConfigSourceRemote];
+    FIRRemoteConfigValue *sourceValueDefault = [config configValueForKey:@"key" source:FIRRemoteConfigSourceDefault];
+    FIRRemoteConfigValue *sourceValueStatic = [config configValueForKey:@"key" source:FIRRemoteConfigSourceStatic];
+
+    [_configInstances[0] objectForKeyedSubscript:@"key"];
+    [_configInstances[0] configValueForKey:@"key"];
+    [_configInstances[0] configValueForKey:@"key" source:FIRRemoteConfigSourceRemote];
+    [_configInstances[0] allKeysFromSource:FIRRemoteConfigSourceRemote];
+    [_configInstances[0] keysWithPrefix:@"prefix"];
+    [_configInstances[0] defaultValueForKey:@"key"];
+    [_configInstances[0] setDefaults:@{}];
+    [_configInstances[0] setDefaultsFromPlistFileName:@"Defaults-testInfo"];
+    
+    [_configInstances[0] configSettings];
+    
+    [_configInstances[0] setCustomSignals:@{} withCompletion:nil];
+    [_configInstances[0] addOnConfigUpdateListener:nil];
+
+    [_configInstances[0] addRemoteConfigInteropSubscriber:nil];
+
+    // Enums
+    FIRRemoteConfigFetchStatus status = FIRRemoteConfigFetchStatusFailure;
+    FIRRemoteConfigFetchAndActivateStatus statusActivate = FIRRemoteConfigFetchAndActivateStatusError;
+    FIRRemoteConfigSource source = FIRRemoteConfigSourceDefault;
+    FIRRemoteConfigError errorCode = FIRRemoteConfigErrorUnknown;
+    FIRRemoteConfigError errorCodeUpdate = FIRRemoteConfigUpdateErrorNotFetched;
+    FIRRemoteConfigError errorCodeCustomSignals = FIRRemoteConfigCustomSignalsErrorUnknown;
+
+    // Enums
+    FIRRemoteConfigFetchStatus fetchStatus = FIRRemoteConfigFetchStatusFailure;
+    FIRRemoteConfigFetchAndActivateStatus fetchAndActivateStatus =
+        FIRRemoteConfigFetchAndActivateStatusError;
+    FIRRemoteConfigSource remoteSource = FIRRemoteConfigSourceRemote;
+
+    //Custom Signals
+    FIRRemoteConfigCustomSignalsError signalCode = FIRRemoteConfigCustomSignalsErrorInvalidValueType;
+    signalCode = FIRRemoteConfigCustomSignalsErrorLimitExceeded;
+    FIRRemoteConfigCustomSignalsError signalCodeUnknown = FIRRemoteConfigCustomSignalsErrorUnknown;
+    NSString *s = FIRRemoteConfigCustomSignalsErrorDomain;
+
+    [_configInstances[0] setCustomSignals:@{@"signal" : @1}];
+    [_configInstances[0] setCustomSignals:@{@"signal" : @1}];
+    NSDictionary<NSString *, NSObject *> *customSignals = @{
+        @"signal1":@"stringValue",
+        @"signal2":@1,
+        @"signal3":@"stringValue2",
+    };
+
+    [_configInstances[0] setCustomSignals:customSignals withCompletion:nil];
+
+    NSString *string = FIRRemoteConfigThrottledEndTimeInSecondsKey;
+    string = FIRRemoteConfigErrorDomain;
+    string = FIRRemoteConfigCustomSignalsErrorDomain;
+    string = FIRRemoteConfigUpdateErrorDomain;
+    NSString *const string2 = @"error_throttled_end_time_seconds";
+    NSString *const string3 = @"error_throttled_end_time_seconds_key";
+}
+
+- (void)testTypes{
+    //typedefs
+    FIRRemoteConfigFetchCompletion completion;
+    FIRRemoteConfigActivateCompletion completion2;
+    FIRRemoteConfigInitializationCompletion completion3;
+    FIRRemoteConfigFetchAndActivateCompletion completion4;
+
+    // Enums
+    FIRRemoteConfigFetchStatus fetchStatus;
+    FIRRemoteConfigFetchAndActivateStatus fetchAndActivateStatus;
+    FIRRemoteConfigSource source = FIRRemoteConfigSourceDefault;
+    source = FIRRemoteConfigSourceRemote;
+    source = FIRRemoteConfigSourceStatic;
+    FIRRemoteConfigError error;
+
+    FIRRemoteConfigError errorCode = FIRRemoteConfigErrorUnknown;
+    errorCode = FIRRemoteConfigErrorThrottled;
+    errorCode = FIRRemoteConfigErrorInternalError;
+
+    FIRRemoteConfigUpdateError errorCodeUpdate = FIRRemoteConfigUpdateErrorNotFetched;
+    errorCodeUpdate = FIRRemoteConfigUpdateErrorStreamError;
+    errorCodeUpdate = FIRRemoteConfigUpdateErrorMessageInvalid;
+    errorCodeUpdate = FIRRemoteConfigUpdateErrorUnavailable;
+
+    FIRRemoteConfigCustomSignalsError signalCode = FIRRemoteConfigCustomSignalsErrorInvalidValueType;
+    signalCode = FIRRemoteConfigCustomSignalsErrorLimitExceeded;
+    signalCode = FIRRemoteConfigCustomSignalsErrorUnknown;
+
+    // FIRRemoteConfigFetchStatus
+    FIRRemoteConfigFetchStatus status;
+    status = FIRRemoteConfigFetchStatusFailure;
+    status = FIRRemoteConfigFetchStatusNoFetchYet;
+    status = FIRRemoteConfigFetchStatusSuccess;
+    status = FIRRemoteConfigFetchStatusThrottled;
+
+    // FIRRemoteConfigFetchAndActivateStatus
+    FIRRemoteConfigFetchAndActivateStatus fetchAndActivateStatus =
+        FIRRemoteConfigFetchAndActivateStatusError;
+    fetchAndActivateStatus = FIRRemoteConfigFetchAndActivateStatusSuccessFetchedFromRemote;
+    fetchAndActivateStatus = FIRRemoteConfigFetchAndActivateStatusSuccessUsingPreFetchedData;
+    fetchAndActivateStatus = FIRRemoteConfigFetchAndActivateStatusError;
+    
+    //FIRRemoteConfigSource
+    FIRRemoteConfigSource remoteSource;
+    remoteSource = FIRRemoteConfigSourceDefault;
+    remoteSource = FIRRemoteConfigSourceRemote;
+    remoteSource = FIRRemoteConfigSourceStatic;
+
+    //FIRRemoteConfigError
+    FIRRemoteConfigError errorCode2 = FIRRemoteConfigErrorUnknown;
+    errorCode2 = FIRRemoteConfigErrorThrottled;
+    errorCode2 = FIRRemoteConfigErrorInternalError;
+
+    // FIRRemoteConfigFetchCompletion
+    FIRRemoteConfigFetchCompletion fetchCompletion;
+
+    // FIRRemoteConfigActivateCompletion
+    FIRRemoteConfigActivateCompletion activateCompletion;
+
+    // FIRRemoteConfigInitializationCompletion
+    FIRRemoteConfigInitializationCompletion initializationCompletion;
+    
+    //FIRRemoteConfigFetchAndActivateCompletion
+    FIRRemoteConfigFetchAndActivateCompletion fetchAndActivateCompletion;
+
+    //FIRRemoteConfigValue
+    FIRRemoteConfigValue *value;
+    NSString *string = value.stringValue;
+    NSNumber *number = value.numberValue;
+    NSData *data = value.dataValue;
+    BOOL boolValue = value.boolValue;
+    id json = value.JSONValue;
+    FIRRemoteConfigSource source = value.source;
+
+    //FIRRemoteConfigUpdate
+    FIRRemoteConfigUpdate *update;
+
+    // FIRRemoteConfigSettings
+    FIRRemoteConfigSettings *setings = [[FIRRemoteConfigSettings alloc] init];
+
+    //NSNotificationName
+    NSNotificationName notificationName;
+    notificationName = FIRRemoteConfigActivateNotification;
+    
+    // NSNotificationName
+    NSNotificationName name;
+    name = FIRRolloutsStateDidChangeNotificationName;
+    
+    // FIRRemoteConfigThrottledEndTimeInSecondsKey
+    NSString *const string2 = @"error_throttled_end_time_seconds";
+
+    //FIRRemoteConfigUpdateError
+    NSString *const string3 = @"error_throttled_end_time_seconds_key";
+
+    //NS_SWIFT_NAME
+    NSString *name2 = FIRNamespaceGoogleMobilePlatform;
+    NSString *name3 = FIRRemoteConfigThrottledEndTimeInSecondsKey;
+    NSString *name4 = FIRRemoteConfigErrorDomain;
+    NSString *name5 = FIRRemoteConfigUpdateErrorDomain;
+    NSString *name6 = FIRRemoteConfigCustomSignalsErrorDomain;
+    NSString *name7 = FIRRemoteConfigUpdateErrorDomain;
+
+    //FIRRemoteConfigFetchStatus
+    FIRRemoteConfigFetchStatus fetchStatus4;
+}
+
+@end