https://github.com/kudashevs/string-calculator-oop
An object-oriented implementation of the string calculator kata.
https://github.com/kudashevs/string-calculator-oop
Last synced: about 2 months ago
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An object-oriented implementation of the string calculator kata.
- Host: GitHub
- URL: https://github.com/kudashevs/string-calculator-oop
- Owner: kudashevs
- License: mit
- Created: 2025-04-02T13:12:19.000Z (about 2 months ago)
- Default Branch: master
- Last Pushed: 2025-04-03T18:03:59.000Z (about 2 months ago)
- Last Synced: 2025-04-03T19:22:30.056Z (about 2 months ago)
- Language: TypeScript
- Homepage: https://kudashevs.com/posts/2025/03/string-calculator-kata-object-oriented-way
- Size: 33.2 KB
- Stars: 0
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE.md
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README
String Calculator kata (Object-Oriented implementation)
==========================
This is an object-oriented implementation of the String Calculator kata.
***Spoiler alert*** If you have never done this kata before, please try to do it before looking at the implementations in the repo.
Otherwise, it won’t be interesting and beneficial.
## Kata's description
***Important note before you start***
* Try not to read ahead.
* Do one task at a time. The trick is to learn to work incrementally.
* Make sure you only test for correct inputs (there is no need to test for invalid inputs for this kata).
### Step 1
Create a simple string calculator with a method signature:
```
int Add(string numbers)
```
The method can take up to two numbers, separated by commas, and will return their sum.
For example `""` or `"1"` or `"1,2"` as inputs (for an empty string it will return 0).
**Hints:**
* Start with the simplest test case of an empty string and move to one and two numbers
* Remember to solve things as simply as possible so that you force yourself to write tests you did not think about
* Remember to refactor after each passing test
### Step 2
Allow the `Add()` method to handle an unknown amount of numbers.
### Step 3
Allow the `Add()` method to handle new lines between numbers (instead of commas).
1. the following input is ok: `"1\n2,3"` (will equal 6)
2. the following input is NOT ok: `"1,\n"` (not need to prove it - just clarifying)
### Step 4
Support different delimiters.
1. to change a delimiter, the beginning of the string will contain a separate line that looks like this: "//[delimiter]\n[numbers…]"
for example `"//;\n1;2"` should return three where the default delimiter is `";"`.
2. the first line is optional. All existing scenarios should still be supported.
### Step 5
Calling `Add()` with a negative number will throw an exception `"negatives not allowed"` - and the negative that was passed.
If there are multiple negatives, show all of them in the exception message.
***STOP HERE*** if you are a beginner. Continue if you can finish the steps so far in less than 30 minutes.
### Step 6
Numbers bigger than 1000 should be ignored, so adding 2 + 1001 = 2.
### Step 7
Delimiters can be of any length with the following format: `"//[delimiter]\n"` for example: "//[***]\n1***2***3" should return 6.
### Step 8
Allow multiple delimiters like this: `"//[delim1][delim2]\n"` for example "//[*][%]\n1*2%3" should return 6.
### Step 9
Make sure you can also handle multiple delimiters with length longer than one char.
### Step 10 (optional)
Look at the code once again and reflect on the end result. Try to ask these questions:
* Why the code is structured in this way? What are the pros and cons of the implementation?
* Are you happy with the implementation? Which parts of the implementation you don't like?
* Does the code comply with the general programming principles (Separation of Concerns, DRY, KISS)?
* Does the code comply with the object-oriented principles (GRASP, SOLID, especially the SRP and OCP)?
* What happens if a new string format is required?
* What happens if the requirements changes in ... (business logic, extraction, validation, filtering)?
* Which parts of the implementation can be improved? How? Why this is an improvement?
* Use AI if you are up to.
## Credits
Credits to [Roy Osherove](http://osherove.com/tdd-kata-1) for the original idea.
## License
The MIT License (MIT). Please see the [License file](LICENSE.md) for more information.