Test 3: Testing main.py output...
SUCCESS: main.py prints the correct message!
Output was: Calculator ready!
Test Add: 5 + 3 = 8
Test Subtract: 10 - 4 = 6
Test Multiply: 6 * 7 = 42
Test Divide: 20 / 5 = 4.0
Test Divide by Zero: 10 / 0 = Error: Division by zero
Main output test passed!