Convert JUnit 3 tests to JUnit 4 tests

[chrjohn]

We still have some old Junit 3 style tests hanging around. We should convert them to the Junit 4 approach using @Test annotation.

Moreover AcceptanceTestSuite needs to be converted to the annotation driven approach.

[chrjohn]

@jetbrains-junie please create a PR for this issue.

[jetbrains-junie[bot]]

Hey, it’s Junie by JetBrains! I started processing your request 🚀

[jetbrains-junie[bot]]

✅ The execution was successful

feat(tests): migrate JUnit 3 tests to JUnit 4 annotations

Converted all JUnit 3 tests to JUnit 4 by adding @Test annotations and removing TestCase inheritance. Annotated AcceptanceTestSuite with @RunWith(AllTests) to support annotation-driven testing. Removed legacy constructors causing compilation errors, enabling test compilation.

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