# Testing

## Running Tests

```bash
make test          # all tests (needs libcfitsio-dev)
make test-cal      # calibration tests only (no cfitsio)
make test-zarr     # FITS conversion tests only
```

## Test Categories

### Unit Tests (cal-core)

Pure math functions with known inputs/outputs:

- Rayleigh-Jeans correction at various frequencies and temperatures
- Gamma computation from synthetic HOT/COLD counts
- Receiver temperature Y-factor
- Bad channel detection edge cases
- Flag bit operations
- Atmospheric transmission at known PWV
- Dump averaging with NaN padding

### Integration Tests (cal-io)

```{eval-rst}
.. list-table::
   :header-rows: 1
   :widths: 25 40 35

   * - Test
     - Purpose
     - Data source
   * - ``parity_hfav``
     - Single-pixel HFAV OTF parity
     - Pre-converted Zarr v3
   * - ``parity_multi``
     - Multi-dataset multi-mode parity
     - Pre-converted Zarr v3
   * - ``roundtrip``
     - L0 read -> calibrate -> L1 write -> L1 read
     - Synthetic
   * - ``generate_l1_test_store``
     - Generate synthetic L1 for downstream tests
     - Synthetic
   * - ``concurrent_write``
     - Parallel Zarr write safety
     - Synthetic
   * - ``dump_parity_data``
     - Export per-channel stats for analysis
     - Pre-converted Zarr v3
```

### Conversion Tests (zarr-fits-core)

- Filename parsing regex (standard, relative, simple patterns)
- FITS value parsing (bool, int, float, string)
- Profile auto-detection

## Parity Methodology

The parity tests compare the engine's output against golden reference
CSVs produced by the legacy kalibrate C++/Fortran code. For each
dataset:

1. Load L0 Zarr store (pre-converted from test FITS data)
2. Calibrate with `KalibrateCompat` physics constants
3. Compare mean $T_{rec}$ per pixel against reference CSV
4. Assert deviation < 1% (acceptance threshold)

The `KalibrateCompat` physics mode reproduces the exact
`h/k = 0.047995` K/GHz constant and f32 truncation behaviour of the
legacy code.

## External Parity Suite

A separate external parity suite lives in `calibrate_parity_tests/`
(sibling directory). It covers **21 datasets** across TP, OTF, chopped,
beam-switch, gain interpolation, and multi-frontend modes. Current
status: **16 PASS, 0 FAIL** with T_sys deviations between 0.4% and 2.7%.

The workspace contains **168 unit/integration tests** total
(`cargo test --workspace`).

## Test Data

Test data lives in `kalibrate_test_lib/` (sibling directory):

- `data_fits/` -- 28 original FITS observation files
- `data_zarr_v3/` -- pre-converted Zarr v3 stores
- `reference_data/` -- 33 golden CSVs + ATM table