Kiwi specs for NSDecimalNumber+Additions (iPhone & iPad)

NSDecimalNumber+Additions.h

@interface NSDecimalNumber (Additions)

+ (NSDecimalNumber *)decimalNumberWithString:(NSString *)string scale:(short)scale;
- (NSDecimalNumber *)decimalNumberByRoundingByScale:(short)scale;

@end

NSDecimalNumber+Additions.m

#import "NSDecimalNumber+Additions.h"

@implementation NSDecimalNumber (Additions)

+ (NSDecimalNumber *)decimalNumberWithString:(NSString *)numberValue scale:(short)scale {
    NSDecimalNumber *decimal = [[self alloc] initWithString:numberValue];
    NSDecimalNumber *decimalRounded = [decimal decimalNumberByRoundingByScale:scale];
    [decimal release];
    return decimalRounded;
}

- (NSDecimalNumber *)decimalNumberByRoundingByScale:(short)scale {
    if (!self) return nil;
    NSDecimal result = [self decimalValue];
    NSDecimalRound(&result, &result, scale, NSRoundPlain); 
    return [NSDecimalNumber decimalNumberWithDecimal:result];
}

@end

NSDecimalNumber+AdditionsSpec.m

#import "NSDecimalNumber+Additions.h"
#import "Kiwi.h"

SPEC_BEGIN(NSDecimalNumber_AdditionsSpec)

describe(@"NSDecimalNumber+Additions", ^{	    
    describe(@"+decimalNumberWithString:scale:", ^{
        it(@"calls +alloc, -initWithString and then -decimalNumberByRoundingByScale:", ^{
            id stringMock = [NSString mock];
            short scale = 3;

            // +alloc
            id decimalAlloced = [NSDecimalNumber mock];
            [NSDecimalNumber stub:@selector(alloc) andReturn:decimalAlloced];

            // -initWithString
            id decimalFromString = [NSDecimalNumber mock];
            [[decimalAlloced should] receive:@selector(initWithString:)
                                   andReturn:decimalFromString withArguments:stringMock];

            // -decimalNumberByRoundingByScale:
            id decimalRounded = [NSDecimalNumber mock];
            [[decimalFromString should] receive:@selector(decimalNumberByRoundingByScale:)
                                      andReturn:decimalRounded withArguments:theValue(scale)];
    
            [[[NSDecimalNumber decimalNumberWithString:stringMock scale:scale] should]
             equal:decimalRounded];
        });
        
        it(@"returns NaN for non-numeric strings", ^{
            NSArray *nonNumericValues = [[NSArray alloc] initWithObjects:
                                         [NSNull null],
                                         @"",
                                         @",",
                                         @"$123",
//                                         @".",     // 0
//                                         @"123f",  // 123
//                                         @"456w",  // 456
//                                         @"123e2", // 12300
//                                         @"-1",    // -1
//                                         @"+1",    // 1
                                         nil];
            for(NSString *nonNumericValue in nonNumericValues) {
                nonNumericValue = [nonNumericValue isEqual:[NSNull null]] ? nil : nonNumericValue;
                [[[NSDecimalNumber decimalNumberWithString:nonNumericValue scale:2] should]
                 equal:[NSDecimalNumber notANumber]];
            }
            [nonNumericValues release];
        });
    });

    describe(@"-decimalNumberByRoundingByScale:", ^{
        it(@"rounds to 2 decimal places", ^{
            NSDictionary *numberValues = [[NSDictionary alloc] initWithObjectsAndKeys:
                                          @"0", @"0",
                                          @"3.2", @"3.2",
                                          @"0.34", @"0.343", // round down
                                          @"0.35", @"0.345", // round up
                                          nil];
            NSDecimalNumber *decimal;
            NSDecimalNumber *decimalRounded;
            for (NSString *input in numberValues) {
                decimal = [[NSDecimalNumber alloc] initWithString:input];
                NSString *output = [numberValues objectForKey:input];
                decimalRounded = [[NSDecimalNumber alloc] initWithString:output];
                [[[decimal decimalNumberByRoundingByScale:2] should] equal:decimalRounded];
                [decimal release];
                [decimalRounded release];
            }
            [numberValues release];
        });
    });
});

SPEC_END