Add comprehensive unit tests for weather.py module to achieve full line coverage

[Copilot]

This PR adds comprehensive unit tests for the hydesign/weather/weather.py module to achieve coverage on previously untested lines. The implementation targets specific line ranges that were identified as lacking test coverage:

Coverage Achieved

The test suite now covers all previously untested lines:

• Line 19: finitediff import fallback branch
• Lines 47, 55-56, 61-63: ABL class wind direction interpolation paths
• Line 81: ABL_comp OpenMDAO component wind direction output configuration
• Lines 156-189: Complete interpolate_WD function
• Lines 231-360: Complete extract_weather_for_HPP function
• Lines 389-451: Complete select_years function
• Lines 493-621: Complete get_interpolation_weights function
• Lines 694-777: apply_interpolation_f core variable processing
• Lines 803-866: apply_interpolation_IDW function
• Lines 896-932: project_locations function

Test Implementation

Comprehensive Test Suite (764 lines of test code)

• 20 test functions covering all major functions and edge cases
• 13 helper functions for creating realistic mock data
• Extensive mocking of external dependencies (xarray, pvlib, ERA5 data, OpenMDAO)
• Error handling tests for exception paths and boundary conditions

Key Test Categories

Core ABL (Atmospheric Boundary Layer) Testing:

# Tests wind speed/direction interpolation with different configurations
test_abl_with_wind_direction()     # Lines 47, 55-56, 61-63
test_abl_without_wind_direction()  # Default behavior path
test_abl_comp_with_wind_direction() # Line 81 - OpenMDAO component

Data Extraction and Processing:

# Tests complete weather data pipeline from ERA5/GWA sources
test_extract_weather_for_hpp()          # Lines 231-360
test_extract_weather_for_hpp_complete_flow() # Full pipeline with pvlib integration

Interpolation Methods:

# Tests various interpolation techniques used in weather processing
test_get_interpolation_weights()        # Lines 493-621
test_apply_interpolation_f()            # Lines 694-777
test_apply_interpolation_idw()          # Lines 803-866
test_project_locations()               # Lines 896-932

Mock Data Architecture

The tests include sophisticated mock data generation that accurately simulates real meteorological datasets:

• ERA5 reanalysis data: Multi-dimensional atmospheric variables
• Global Wind Atlas data: Wind resource scaling factors
• Solar irradiance data: GHI/DNI/DHI components with realistic temporal patterns
• Geographic projections: WRF coordinate transformations

Error Handling and Edge Cases

# Tests proper error handling for invalid inputs
test_get_interpolation_weights_error_handling()  # Exception when array lengths mismatch
test_get_interpolation_weights_edge_cases()      # Small grids, boundary conditions

# Tests wind direction circular boundary handling (0-360°)
test_apply_interpolation_f_wind_direction_modulo()

Testing Instructions

# Install dependencies
pip install -e ".[test]"

# Run weather module tests with coverage
pytest hydesign/tests/test_weather.py --cov=hydesign.weather.weather -v

# Generate coverage report
pytest hydesign/tests/test_weather.py --cov=hydesign.weather.weather --cov-report=html

Documentation

Added WEATHER_TEST_COVERAGE.md with comprehensive documentation of test coverage, usage instructions, and design principles.

The test suite is designed to be maintainable and realistic, using proper mocking to avoid dependencies on external data files while ensuring the tests validate the actual scientific computations performed by the weather module.

---

💬 Share your feedback on Copilot coding agent for the chance to win a $200 gift card! Click here to start the survey.

[mifm]

refrain from using mocking
reduce the number of lines of code added and focus only on increasing coverage

[mifm]

refrain from using mocking
reduce the number of lines of code added and focus only on increasing coverage