Implement -testPositive.

SecondsFormatterTests/SecondsFormatterTests.m

@@ -32,6 +32,36 @@
     // Use XCTAssert and related functions to verify your tests produce the correct results.
 }
 
+- (void)testPositive
+{
+	NSDictionary *testsDict =
+	@{
+		// key: test name, value: test string
+		//@"Example": @"0:00",
+		@"One Second": @"0:01",
+		@"One Minute": @"1:00",
+		@"One Hour": @"1:00:00",
+		@"One Day": @"1:00:00:00",
+		@"One of Each": @"1:01:01:01",
+	};
+	
+#define TEST_INFO	@"Test name: %@, Source string: %@", testName, string
+	
+	NSFormatter *secondsFormatter = [[SecondsFormatter alloc] init];
+
+	[testsDict enumerateKeysAndObjectsUsingBlock:
+	 ^(NSString *testName, NSString *string, BOOL * _Nonnull stop) {
+		NSNumber *value;
+		BOOL result =
+		[secondsFormatter getObjectValue:&value
+							   forString:string
+						errorDescription:NULL];
+		XCTAssertTrue(result, TEST_INFO);
+		NSString *timeString = [secondsFormatter stringForObjectValue:value];
+		XCTAssertEqualObjects(string, timeString, TEST_INFO);
+	}];
+}
+
 #if 0
 - (void)testPerformanceExample
 {