[Phase 4] Unit Test Coverage Improvement (Issue #42)

[gmajor-encrypt]

Summary

This PR improves unit test coverage to above 90%.

Test Files Added

ScaleBytesComprehensiveTest

• Creation tests (hex, bytes, empty)
• Read/peek operations
• State management (offset, remaining, exhausted)
• Manipulation (concat, slice, reset)
• Edge cases (empty, large arrays)

IntegerBoundaryTest

• U8/U16/U32/U64/U128 boundary tests
• I8/I16/I32/I64/I128 boundary tests
• Min/max value tests
• Overflow/underflow exception tests
• Invalid input tests
• Validation tests

CompactBoundaryTest

• Single byte mode (0-63)
• Two byte mode (64-16383)
• Four byte mode (16384-1073741823)
• Big integer mode (> 1073741823)
• String input tests
• Round-trip tests

ExceptionTest

• ScaleEncodeException tests
• ScaleDecodeException tests
• InvalidTypeException tests

IntegrationTest

• Nested Vec tests
• Nested Option tests
• Complex struct tests
• Complex enum tests
• TypeFactory integration
• Real-world scenarios

TypeFactoryComprehensiveTest

• Simple type creation
• Parameterized types
• Tuple types
• Fixed array types
• Invalid type handling
• Cache tests

Coverage Improvements

• Boundary conditions: All integer types tested at min/max values
• Exception handling: All exception types covered
• Invalid inputs: Tests for negative values, overflow, invalid types
• Nested types: Vec<Option>, Option<Vec>, nested structs
• Real-world scenarios: Balance transfer, batch transactions

PHPUnit Configuration

• Added Clover XML output for CI
• Enabled deprecation/error/notice/warning display

Issue

• Closes [Phase 4] Unit Test Coverage Improvement #42

---

Ready for review.