Add UnitTests for setLanguage

* Add testSetLanguageOnPlayerCreate to test setLanguage implementation when user is initializing OneSignal implementation
* Add testSetLanguageRequest to test setLanguage after user has initialized OneSignal implementation
* Add testSetLanguage_afterOnSession to test setLanguage method after a session has finished

Author: tanaynigam

iOS_SDK/OneSignalSDK/UnitTests/LanguageTest.m

@@ -0,0 +1,72 @@
+//
+//  LanguageTest.m
+//  OneSignal
+//
+//  Created by Tanay Nigam on 6/24/21.
+//  Copyright © 2021 Hiptic. All rights reserved.
+//
+
+#import <XCTest/XCTest.h>
+#import "UnitTestCommonMethods.h"
+#import "OneSignalUserDefaults.h"
+#import "OneSignal.h"
+#import "OneSignalClientOverrider.h"
+#import "OneSignalHelper.h"
+#import "NSDateOverrider.h"
+
+@interface LanguageTest : XCTestCase
+
+@end
+
+@implementation LanguageTest
+
+- (void)setUp {
+    [super setUp];
+    [UnitTestCommonMethods beforeEachTest:self];
+}
+
+- (void)tearDown {
+    [super tearDown];
+}
+
+- (void)testSetLanguageOnPlayerCreate {
+    [UnitTestCommonMethods initOneSignal_andThreadWait];
+    [OneSignal setLanguage:@"fr"];
+    [UnitTestCommonMethods runBackgroundThreads];
+
+    XCTAssertEqualObjects(OneSignalClientOverrider.lastHTTPRequest[@"language"], @"fr");
+}
+
+- (void)testSetLanguageRequest {
+    [UnitTestCommonMethods initOneSignal_andThreadWait];
+    [UnitTestCommonMethods runBackgroundThreads];
+    [OneSignal setLanguage:@"fr"];
+    [UnitTestCommonMethods runBackgroundThreads];
+
+    XCTAssertEqualObjects(OneSignalClientOverrider.lastHTTPRequest[@"language"], @"fr");
+}
+
+-(void)testSetLanguage_afterOnSession {
+    // 2. Open app
+    [UnitTestCommonMethods initOneSignal_andThreadWait];
+    [UnitTestCommonMethods foregroundApp];
+    [UnitTestCommonMethods runBackgroundThreads];
+
+    // 3. Kill the app and wait 31 seconds
+    [UnitTestCommonMethods backgroundApp];
+    [UnitTestCommonMethods clearStateForAppRestart:self];
+    [NSDateOverrider advanceSystemTimeBy:31];
+    [UnitTestCommonMethods runBackgroundThreads];
+
+    // 4. Open app
+    [UnitTestCommonMethods initOneSignal_andThreadWait];
+    [UnitTestCommonMethods foregroundApp];
+    [UnitTestCommonMethods runBackgroundThreads];
+    
+    [OneSignal setLanguage:@"fr"];
+    [UnitTestCommonMethods runBackgroundThreads];
+
+    XCTAssertEqualObjects(OneSignalClientOverrider.lastHTTPRequest[@"language"], @"fr");
+}
+
+@end