# Subroutines

Subroutines allow direct testing of internal contract logic without full application calls.

```
import algopy

import algopy_testing

from algopy_testing import algopy_testing_context

# Create the context manager for snippets below

ctx_manager = algopy_testing_context()

# Enter the context

context = ctx_manager.__enter__()
```

## Overview

The `@algopy.subroutine` decorator exposes contract methods for isolated testing within the Algorand Python Testing framework. This enables focused validation of core business logic without the overhead of full application deployment and execution.

## Usage

1. Decorate internal methods with `@algopy.subroutine`:

```
from algopy import subroutine, UInt64

class MyContract:

@subroutine

def calculate_value(self, input: UInt64) -> UInt64:

return input * UInt64(2)
```

2. Test the subroutine directly:

```
def test_calculate_value(context: algopy_testing.AlgopyTestContext):

contract = MyContract()

result = contract.calculate_value(UInt64(5))

assert result == UInt64(10)
```

## Benefits

- Faster test execution
- Simplified debugging
- Focused unit testing of core logic

## Best Practices

- Use subroutines for complex internal calculations
- Prefer writing `pure` subroutines in ARC4Contract classes
- Combine with full application tests for comprehensive coverage
- Maintain realistic input and output types (e.g., `UInt64`, `Bytes`)

## Example

For a complete example, see the `simple_voting` contract in the [examples](https://dev.algorand.co/algokit/unit-testing/python/examples) section.

```
ctx_manager.__exit__(None, None, None)
```