Environment Variables Reference¶

This page documents all environment variables used by the Hera system, organized by context.

Runtime Variables¶

These variables affect how Hera operates in normal production use.

Variable	Required	Default	Description
`HOME`	Yes (OS)	OS default	Used to locate the MongoDB config file at `~/.pyhera/config.json`. This is a standard OS variable and is always set.
`MPLBACKEND`	No	system default	Matplotlib backend selection. Set to `Agg` for headless (no GUI) operation, e.g., on servers or in CI/CD pipelines.

MongoDB Configuration¶

The MongoDB connection is not configured via environment variables but through the JSON config file at ~/.pyhera/config.json:

{
    "connectionName": {
        "username": "your_username",
        "password": "your_password",
        "dbIP": "localhost:27017",
        "dbName": "hera_db"
    }
}

See Installation for setup instructions.

Testing Variables¶

These variables control the behavior of the Pytest test suite.

Variable	Required	Default	Description
`TEST_HERA`	No	`~/hera_unittest_data`	Root directory containing the test data repository. This directory should contain `test_repository.json`, `data_config.json`, `measurements/`, and `expected/` subdirectories.
`RESULT_SET`	No	`BASELINE`	Name of the expected-output result set to compare against. Must correspond to a directory under `expected/` in the test data root.
`PREPARE_EXPECTED_OUTPUT`	No	unset	When set to `"1"`, switches the test suite into generation mode: tests write their current outputs as the new expected baselines instead of comparing against existing ones.
`GDF_TOL_AREA`	No	`1e-7`	Tolerance for geometry comparison in GeoDataFrame tests. The comparison uses `symmetric_difference().area` and checks that the area is below this threshold.
`HERA_FULL_LOGGING_TESTS`	No	unset	When set (to any value), enables full logging output during test runs. When unset, verbose logging tests are skipped.
`PYARGOS_PATH`	No	unset	Optional developer-set path to a local `pyargos-master` (PyArgos) installation. Used only by `hera/tests/dynamic_loading_tests_pack/test_experiment_cli_shortcuts.py`, which prepends this directory to `PYTHONPATH` so the experiment toolkit CLI can locate PyArgos. If unset or the path does not exist, the related tests fall back to the default environment.

Usage Examples¶

# Run tests with default settings
pytest hera/tests/ -v

# Run tests against a specific result set
RESULT_SET=REGRESSION_2025_11_11 pytest hera/tests/ -v

# Generate new expected outputs (baseline creation)
PREPARE_EXPECTED_OUTPUT=1 pytest hera/tests/ -v

# Use custom test data location
TEST_HERA=/data/test_data pytest hera/tests/ -v

# Headless matplotlib for CI
MPLBACKEND=Agg pytest hera/tests/ -v

# Combine multiple settings
MPLBACKEND=Agg RESULT_SET=BASELINE TEST_HERA=/data/test pytest hera/tests/ -v

Variable Resolution Priority¶

For the result set selection, the system uses the following priority chain:

Diagram

g -- "Yes" --> UseConfig["Use config value"] CheckConfig -- "No" --> UseFallback["Use 'BASELINE'\nhardcoded fallback"]

-->
-->g -- "Yes" --> UseConfig["Use config value"]
    CheckConfig -- "No" --> UseFallback["Use 'BASELINE'\nhardcoded fallback"]

--> -->

Test Data Directory Structure¶

The TEST_HERA directory should follow this layout:

$TEST_HERA/                          # Default: ~/hera_unittest_data
├── data_config.json                 # Metadata and result set defaults
├── test_repository.json             # Hera repository JSON mapping
├── measurements/                    # Test data files
│   ├── GIS/
│   │   ├── raster/                  # HGT, TIF files
│   │   └── vector/                  # SHP, GeoJSON files
│   └── meteorology/
│       ├── lowfreqdata/             # Parquet station data
│       └── highfreqdata/            # High-frequency parquet data
└── expected/                        # Expected output result sets
    ├── BASELINE/                    # Default result set
    │   ├── *.parquet                # DataFrame outputs
    │   ├── *.json                   # Dict/scalar outputs
    │   ├── *.nc                     # xarray outputs
    │   └── *.npz                    # NumPy array outputs
    └── REGRESSION_YYYYMMDD/         # Named regression sets

Setting Variables Permanently¶

Linux / macOS¶

Add to your shell profile (~/.bashrc, ~/.zshrc, etc.):

# Hera test configuration
export TEST_HERA="$HOME/hera_unittest_data"
export MPLBACKEND="Agg"

Per-Project (.env file)¶

If using tools like direnv or IDE-specific env files:

TEST_HERA=/home/user/hera_unittest_data
MPLBACKEND=Agg
RESULT_SET=BASELINE

In pytest.ini¶

Some variables can be set in pytest.ini using the env plugin:

[pytest]
env =
    MPLBACKEND=Agg