# How to Test Combinations of Parameters
## Contents
- [Why use Combinations](#why-use-combinations)
- [Cartesian product](#cartesian-product)
- [Steps](#steps)
- [See Also](#see-also)
## Why use Combinations
Combination Approvals allows you to test hundreds of calls to a function using different parameter values with just a few lines of code.
For example, you have a function that takes 3 parameters, and you want to test its behaviour with a bunch of different values for each of those parameters.
### Cartesian product
Combinations will test the Cartesian product of all possibilities for each parameter.
For example:
If you have **3 names**, **4 ages** and **5 cities**,
it will call the function being tested with all
[3 X 4 X 5] = **60 permutations** of the arguments.
## Steps
1. Copy this starter text, and adjust for the number of inputs that you have.
```mts
test("CombinationsStartingPoint", () => {
const inputs1 = ["input1.value1", "input1.value2"];
const inputs2 = ["input2.value1", "input2.value2", "input2.value3"];
verifyAllCombinations2(
(a, b) => `placeholder for ${a}, ${b}`,
inputs1,
inputs2,
);
});
```
snippet source | anchor
2. Modify each input container for your chosen values.
3. Make sure each input type can be converted to a string (See [Tips for Designing Strings](https://approvaltestscpp.readthedocs.io/en/latest/generated_docs/explanations/TipsForDesigningStrings.html))
4. Run it, and make sure that you have your inputs wired up correctly.
If they are wired up correctly, you will see a file that looks like this: it is the left hand side of the file that
matters at this point: all combinations of your own input values should be listed:
```txt
[input1.value1,input2.value1] => placeholder for input1.value1, input2.value1
[input1.value1,input2.value2] => placeholder for input1.value1, input2.value2
[input1.value1,input2.value3] => placeholder for input1.value1, input2.value3
[input1.value2,input2.value1] => placeholder for input1.value2, input2.value1
[input1.value2,input2.value2] => placeholder for input1.value2, input2.value2
[input1.value2,input2.value3] => placeholder for input1.value2, input2.value3
```
snippet source | anchor
5. Implement the body of your lambda
6. Run it, and approve the output.
## See Also
- [Combinations Approvals](../reference/CombinationApprovals.md)
---
[Back to User Guide](/doc/README.md#top)