assertion-synthesizer

Assertion Synthesizer

Generate comprehensive test assertions by analyzing code implementation, behavior, and expected outputs.

Workflow

1. Analyze Code

Read and understand the implementation to identify testable behavior:

• Function signatures: Parameters, return types, side effects
• Logic paths: Conditionals, loops, branching behavior
• Edge cases: Boundary conditions, null/empty inputs, error conditions
• State changes: Object mutations, attribute modifications
• Dependencies: External calls, database operations, I/O

2. Identify Test Scenarios

Extract scenarios that need assertions:

• Happy path: Normal inputs producing expected outputs
• Edge cases: Empty lists, zero values, boundary conditions
• Error cases: Invalid inputs, exceptions, error handling
• State verification: Object state before/after operations
• Collection assertions: List contents, ordering, membership

3. Generate Assertions

Create appropriate assertions for each scenario:

Assertion Types:

• Equality: assert result == expected, assertEquals(expected, actual)
• Truthiness: assert is_valid, assertTrue(condition)
• Collections: assert item in list, assertContains(list, item)
• Exceptions: pytest.raises(Exception), assertThrows(Exception)
• State: assert obj.status == "active", assertEquals("active", obj.getStatus())

4. Structure Tests

Organize assertions into well-structured test functions:

• Use descriptive test names
• Follow Arrange-Act-Assert pattern
• Group related assertions
• Add explanatory comments

5. Verify Coverage

Ensure all important behaviors have assertions:

• Check all return values are tested
• Verify edge cases are covered
• Confirm error conditions are tested
• Validate state changes are asserted

Language-Specific Patterns

Python (pytest)

def test_basic_equality():
    # Arrange
    calculator = Calculator()

    # Act
    result = calculator.add(2, 3)

    # Assert
    assert result == 5

def test_collection_membership():
    items = get_active_items()
    assert "item1" in items
    assert len(items) == 3

def test_exception_handling():
    with pytest.raises(ValueError, match="Invalid input"):
        process_data(None)

def test_state_change():
    user = User("Alice")
    user.activate()
    assert user.is_active == True
    assert user.status == "active"