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Architecture Tests

This project uses ArchUnit to enforce architectural constraints and detect design smells.

Current Architecture Tests

✅ Passing Tests

  1. packages_should_be_free_of_cycles()

    • Verifies no cyclic dependencies between top-level packages
    • Pattern: edu.luc.etl.cs313.android.simplestopwatch.(*)

  2. subpackages_should_be_free_of_cycles()

    • Verifies no cyclic dependencies at sub-package level
    • Pattern: edu.luc.etl.cs313.android.simplestopwatch.(*).(*)

❌ Failing Tests (Demonstrating Architecture Violations)

  1. model_should_only_depend_on_java_common_or_model()

    • Purpose: Ensures model layer is self-contained
    • Allowed Dependencies: java.*, javax.*, ..common.*, ..model.*
    • Current Violations (4):
      • LapRunningState.getId() → R$string.LAP_RUNNING
      • LapStoppedState.getId() → R$string.LAP_STOPPED
      • RunningState.getId() → R$string.RUNNING
      • StoppedState.getId() → R$string.STOPPED

  2. model_should_not_depend_on_R_class()

    • Purpose: Explicitly forbids dependencies on Android resource class R
    • Rationale: Model classes should not depend on UI-specific resources
    • Current Violations (4): Same as test #3 above

Technical Notes

Why R.java Uses Integer.valueOf()

The R class uses Integer.valueOf() instead of literal integer constants:

public static final int STOPPED = Integer.valueOf(0);  // Not: = 0;

Reason: Java's compiler performs compile-time constant inlining for static final primitive fields with literal values. This means:

  • With int STOPPED = 0; → Compiler replaces R.string.STOPPED with 0 in bytecode
  • With int STOPPED = Integer.valueOf(0); → Bytecode contains getstatic R$string.STOPPED

ArchUnit operates on compiled bytecode, not source code. If constants were inlined, ArchUnit couldn't detect the dependency because it wouldn't exist in the bytecode—only in the source.

By using Integer.valueOf(), we ensure the dependency exists at runtime, making it detectable by ArchUnit.

Bytecode Comparison

With literal constant (inlined):

public int getId();
  Code:
    0: iconst_0    // Push constant 0
    1: ireturn

With Integer.valueOf() (not inlined):

public int getId();
  Code:
    0: getstatic #37  // Field R$string.STOPPED:I
    3: ireturn

Running the Tests

# Run all architecture tests
./gradlew test --tests "*.PackageDependencyTest"

# Run specific test
./gradlew test --tests "*.PackageDependencyTest.model_should_not_depend_on_R_class"

# Run with detailed violation output
./gradlew test --tests "*.PackageDependencyTest" --info

How to Fix the Violations

To eliminate the architectural violations, the R class constants should be moved to the common package or the state classes should use a different mechanism for state identification that doesn't depend on UI resources.

For example:

  1. Move constants to Constants.java in the common package
  2. Have states return their own type/class as identification
  3. Use an enum for state identification