Add hardcoded unit tests for bitflip operations

[Copilot]

The bitflip test suite relied primarily on reversibility checks and probabilistic tests. This PR adds deterministic tests with predetermined input-output pairs to verify bitflips occur at correct positions with correct transformations.

Changes

• New test file: tests/unit_tests/test_bitflip_hardcoded.py with 19 test methods covering:

  • Sign bit flips (bit 0): 1.0 → -1.0, -5.0 → 5.0
  • Exponent bit flips: bitflip(1.0, 1) → inf (exponent becomes all 1s)
  • Mantissa LSB flips: minimal float32 precision changes
  • Matrix position-specific flips: [[0,1],[2,3]] with bit 0 at [1,1] → [[0,1],[2,-3]]
  • Implementation consistency across bitflip_float32, bitflip_float32_optimized, and bitflip_float32_fast

• Documentation: MSB-first indexing convention explicitly documented (bit 0 = sign, bits 1-8 = exponent, bits 9-31 = mantissa)

Example

# Test sign bit flip with known outcome
assert bitflip_float32(3.0, 0) == -3.0

# Test matrix operation from issue
matrix = np.array([[0.0, 1.0], [2.0, 3.0]], dtype=np.float32)
matrix[1, 1] = bitflip_float32(matrix[1, 1], 0)  # 3.0 → -3.0
assert matrix[1, 1] == -3.0

All 111 unit tests pass with 96% coverage.

Original prompt

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This section details on the original issue you should resolve

<issue_title>[FEATURE] Add better hardcoded unit tests</issue_title>
<issue_description>### Feature Summary

I want some stronger checks that the bitflips are being performed in the correct location and in the correct way.

Feature Category

Testing/Quality Assurance

Problem Statement

I want some stronger checks that the bitflips are being performed in the correct location and in the correct way.

Proposed Solution

Have some hardcoded tests. i.e. take a matrix [[0,1],[2,3]] and do a bit_i=0 at [1,1] to be [[0,1],[2,-3]]

Proposed API (if applicable)

Priority Level

None

Research Impact

No response

Alternatives Considered

No response

Implementation Considerations

• This feature requires new dependencies
• This feature affects performance-critical paths
• This feature requires GPU/CUDA support
• This feature needs extensive testing
• This feature affects the public API
• I would be interested in implementing this feature

Additional Context

No response

Pre-submission Checklist

• I have searched existing issues for similar requests
• I have provided sufficient detail about the use case
• I have considered the impact on existing users
• I have thought about backward compatibility</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes [FEATURE] Add better hardcoded unit tests #22

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