filling_tests_dev_fork.md

Filling Tests for Features under Development

Requirements

By default, execution-spec-tests only generates fixtures for forks that have been deployed to mainnet. In order to generate fixtures for evm features that are actively under development:

1. A version of the evm and solc tools that implement the feature must be available (although, typically only a developer version of the evm tool is required, usually the latest stable release of solc is adequate), and,

2. The development fork to test must be explicitly specified on the command-line:

   === "via the --fork flag"

      ```console
      fill -k 4844 --fork=Cancun -v
      ```
   

   === "via the --from flag"

      ```console
      fill -k 4844 --from=Cancun -v
      ```
   

   === "via the --until flag"

      ```console
      fill -k 4844 --until=Cancun -v
      ```
   

!!! note "Specifying the evm binary via evm-bin" It is possible to explicitly specify the evm binary used to generate fixtures via the --evm-bin flag, for example,

 ```console
 fill --fork=Cancun --evm-bin=/opt/bin/evm -v
 ```

Further Help

1. geth/evm build documentation.
2. solc build documentation.

!!! note "Verifying evm and solc versions used" The versions used to generate fixtures are displayed in the console output:

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VS Code Setup

By default, VS Code's Testing View will only show tests for stable forks. To show tests for development forks, uncomment the relevant line in the python.testing.pytestArgs configuration section of included settings file (.vscode/settings.json) to enable the --until=FORK flag. See VS Code Setup for help finding the settings files.