Fixing the pytest errors

[JAGADISHSUNILPEDNEKAR]

Fix test failures by adding development mode installation instructions

This PR addresses issue #158 where a new contributor encountered multiple test failures when running the test suite. The primary issue was the lack of clear instructions for installing the package in development mode before running tests.

Changes made:

1. Updated CONTRIBUTING.md to explicitly instruct contributors to run pip install -e . before running tests
2. Added a new "Troubleshooting Test Failures" section that explains common test failure scenarios and how to address them

Why this fix is needed:

Without installing the package in development mode, the test modules cannot properly discover and import the local code, resulting in various import errors and API mismatch errors as seen in issue #158.

The test failures specifically showed:

• Module import errors
• Public Key class API mismatch errors
• Transaction hex assertion errors

These are all symptoms of the tests not being able to correctly access the package modules, which is resolved by the development mode installation.

Testing:

I've verified this approach by:

1. Running tests without development mode installation (reproducing the errors)
2. Installing in development mode with pip install -e .
3. Confirming that tests pass after proper installation

This documentation improvement should help new contributors avoid the same pitfalls when setting up their development environment.

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