# Inline configuration for Solidity tests

Description: How to use inline comments to override the solidity tests' configuration

Note: This document was authored using MDX

  Source: https://github.com/NomicFoundation/hardhat-website/tree/main/src/content/docs/docs/guides/testing/inline-configuration.mdx

Hardhat lets you override solidity test settings on a per-function basis using NatSpec comments. This is useful when different tests need different parameters. For example, running more fuzz iterations on a critical function, or increasing the depth of an invariant test.

Inline overrides take precedence over the global settings defined in your [Solidity tests configuration](/docs/reference/configuration#solidity-tests-configuration).

## Syntax

Each override is a single line inside a NatSpec comment (line `///` or block `/** */`), following the format `hardhat-config: <key> = <value>`.

Keys can be written in camelCase, snake_case, or kebab-case, and string values must be double-quoted:

```solidity
/// hardhat-config: fuzz.runs = 10000
/// hardhat-config: fuzz.maxTestRejects = 500
/// hardhat-config: evmVersion = "cancun"
function testTransferFuzz(uint256 amount) public {
  // ...
}
```

Block comments are also supported:

```solidity
/**
 * hardhat-config: invariant.runs = 100
 * hardhat-config: invariant.depth = 50
 * hardhat-config: invariant.failOnRevert = true
 */
function invariantBalanceAlwaysPositive() public {
  // ...
}
```

## Supported configuration keys

Keys with the `fuzz.`/`invariant.` prefix apply only to that test type; the rest apply to the test as a whole and work on both fuzz and invariant tests.

| Key                         | Description                                                              |
| --------------------------- | ------------------------------------------------------------------------ |
| `fuzz.runs`                 | Number of fuzz iterations to run                                         |
| `fuzz.maxTestRejects`       | Maximum number of rejected inputs before aborting                        |
| `fuzz.showLogs`             | Whether to show console logs during fuzzing                              |
| `fuzz.timeout`              | Timeout for the fuzz test                                                |
| `invariant.runs`            | Number of invariant test runs                                            |
| `invariant.depth`           | Number of calls per run to attempt to break the invariant                |
| `invariant.failOnRevert`    | Whether to fail the invariant if a revert occurs                         |
| `invariant.callOverride`    | Whether to override unsafe external calls                                |
| `invariant.timeout`         | Timeout for the invariant test                                           |
| `allowInternalExpectRevert` | See [below](#allowinternalexpectrevert)                                  |
| `isolate`                   | Run each top-level call as a separate transaction in its own EVM context |
| `evmVersion`                | EVM version to use for this test                                         |

### `allowInternalExpectRevert`

By default, the `expectRevert` cheatcode only catches reverts from external calls, that is, calls at a lower depth than the test itself. If your test directly calls an internal function that reverts, `expectRevert` won't catch it and you'll see an error like `call didn't revert at a lower depth than cheatcode call depth`.

Setting `allowInternalExpectRevert` to `true` allows `expectRevert` to work on calls at the same depth as the test:

```solidity
/// hardhat-config: allowInternalExpectRevert = true
function testInternalRevert() public {
  vm.expectRevert("some error");
  this.myInternalHelper(); // reverts at the same call depth
}
```

## Foundry compatibility

Hardhat also accepts the `forge-config:` prefix and the `default` profile, so existing Foundry inline configuration works without changes:

```solidity
/// forge-config: default.fuzz.runs = 10000
/// forge-config: fuzz.max-test-rejects = 500
function testTransferFuzz(uint256 amount) public {
  // ...
}
```

Omitting the profile is equivalent to using `default`.