Question

I want to write unit tests using Apple’s default SenTestingKit for the below method:

- (NSDictionary*)getValueTags {
    return _tags;
}

- (NSString*)getFlag {
    NSString* jo = @"";
    for (NSString* key in _tags) {
        jo = [jo stringByAppendingFormat:@"%@=\"%@\"&", key, [_tags objectForKey:key]];
    }
    if ([jo length] > 0) {
        jo = [jo substringToIndex:[jo length] - 1];
    }
    return jo;
}

I used default SenTesting

    - (void)setUp
    {
        [super setUp];

        // Set-up code here.
    }

    - (void)tearDown
    {
        // Tear-down code here.

        [super tearDown];
    }

-(void)testValueTags{

}

-(void)testGetFlag{

}

I am new to writing TestCases, I need some guideline for sample methods to write test cases

Answer 1

A test case has four distinct phases:

1. set up
2. exercise
3. verify
4. tear down

Some of these phases can be empty. For example, most tear down happens automatically if you use ARC.

When you’re starting, don’t put anything into the setUp or tearDown methods. Just write a single unit test. Here’s a worked example. (I’m going to change the names, because Objective-C idiom is not to use the word “get”. So instead of getFlag let’s just call it flag.) I’m going to call the class `Example, and I’ll use ARC. And I use the abbreviation “sut” for “system under test”.

- (void)testFlagGivenOneEntry
{
    // set up
    Example *sut = [[Example alloc] init];
    [sut setTags:@{ @"key1" : @"value1" }];

    // execute & verify
    STAssertEqualObjects([sut flag], @"key1=\"value1\"", nil);
}

That’s one test. Let’s add another.

- (void)testFlagGivenTwoEntries
{
    // set up
    Example *sut = [[Example alloc] init];
    [sut setTags:@{ @"key1" : @"value1",
                    @"key2" : @"value2" }];

    // execute & verify
    STAssertEqualObjects([sut flag], @"key1=\"value1\"&key2=\"value2\"", nil);
}

At this point, we have duplicate code: the creation of the sut. Now we can promote the variable up to an instance variable of the class. Then we create it in setUp and destroy it in tearDown:

@interface ExampleTest : SenTestCase
@end

@implementation ExampleTest
{
    Example *sut;
}

- (void)setUp
{
    [super setUp];
    sut = [[Example alloc] init];
}

- (void)tearDown
{
    sut = nil;
    [super tearDown];
}

- (void)testFlagGivenOneEntry
{
    [sut setTags:@{ @"key1" : @"value1" }];
    STAssertEqualObjects([sut flag], @"key1=\"value1\"", nil);
}

- (void)testFlagGivenTwoEntries
{
    [sut setTags:@{ @"key1" : @"value1",
                    @"key2" : @"value2" }];
    STAssertEqualObjects([sut flag], @"key1=\"value1\"&key2=\"value2\"", nil);
}

@end

For a more involved example, see Objective-C TDD: How to Get Started.