[Bug] Flask /compile route has zero test coverage due to incorrect mock in test_compile_code

[sakshamg19]

Description

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test_compile_code in gdbui_server/flask_test.py mocks self.client.post which is the Flask test client itself. This means the /compile route handler never runs during the test. The test just checks that a mock returns what it was set up to return, so it will always pass no matter what the real code does.

Every line of the actual /compile handler is untested:

• request.get_json()
• open(f'{name}.cpp', 'w')
• subprocess.run(['g++', ...])
• the success response
• the failure response

Steps to Reproduce

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1. Open gdbui_server/flask_test.py
2. Look at test_compile_code around line 29
3. Line 31 patches self.client.post with a mock
4. This replaces the HTTP transport so /compile never gets called

Expected behaviour

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The test should send a real request to /compile and check the route actually works, only mocking subprocess.run so tests don't depend on g++ being installed.

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Proposed fix

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The test should mock subprocess.run instead of self.client.post. This way the Flask test client sends a real HTTP request to /compile, the route handler actually executes and only the g++ subprocess call at the system boundary gets mocked (since tests should not depend on g++ being installed in the CI environment).

The two tests that should replace the current one are:

• test_compile_code: This mocks subprocess.run with returncode=0, sends a real request, verifies the route writes the source file to disk, calls g++ with the correct arguments and returns success: true with the right output message
• test_compile_code_failure: mocks subprocess.run with returncode=1 and a stderr error message, verifies the route returns success: false with the compiler error in the output

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