Expand unit test coverage for JSON I/O, Prompt, and Tavern modules

[Copilot]

Overview

This PR significantly expands the unit test coverage for the FishE project, adding 12 new test functions across 5 test files. The changes focus on previously untested or under-tested modules, particularly file I/O operations and edge cases.

Changes Made

New Test File

• tests/prompt/test_prompt.py - Created comprehensive tests for the Prompt class, which previously had no test coverage

Enhanced Test Coverage

JSON Reader/Writer Classes

Added file I/O tests for all three JSON reader/writer classes:

• playerJsonReaderWriter.py - Added test_writePlayerToFile and test_readPlayerFromFile to verify serialization/deserialization
• statsJsonReaderWriter.py - Added test_writeStatsToFile and test_readStatsFromFile to verify stats persistence
• timeServiceJsonReaderWriter.py - Added test_writeTimeServiceToFile and test_readTimeServiceFromFile to verify time tracking persistence

These tests use temporary files to ensure file I/O operations work correctly and handle data round-trips properly.

Tavern Gambling Logic

Enhanced tavern tests with additional edge case coverage:

• test_gamble_loss - Tests the gambling loss scenario and stat tracking
• test_changeBet_insufficient_money - Tests error handling when player bets more than they have
• test_changeBet_invalid_input - Tests handling of non-numeric input
• test_getDrunk_updates_stats - Verifies stat updates when getting drunk

Coverage Improvements

• Overall project coverage: 84% → 87% (+3%)
• playerJsonReaderWriter.py: 80% → 100% ✅
• statsJsonReaderWriter.py: 80% → 100% ✅
• timeServiceJsonReaderWriter.py: 75% → 100% ✅
• prompt.py: 0% → 100% ✅
• tavern.py: 65% → 70% (+5%)

Testing

All 78 tests pass successfully:

$ python3 -m pytest --cov=src --cov-report=term
78 passed in 0.73s
TOTAL coverage: 87%

Notes

All new tests follow the existing test patterns in the repository (prepare/call/check structure) and use appropriate mocking to avoid side effects. The tests are focused on validating core functionality and edge cases without modifying any production code.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Expand unit tests</issue_title>
<issue_description>Create or expand unit tests</issue_description>

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

Fixes #40

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