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 TEST-DRIVEN CALCULATOR (COURSE CAPSTONE) - Demo Run
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--- Running the REAL unittest suite (genuine red/green results) ---
test_add_negative_numbers (__main__.TestCalculator.test_add_negative_numbers) ... ok
test_add_two_positive_numbers (__main__.TestCalculator.test_add_two_positive_numbers) ... ok
test_divide_by_zero_raises (__main__.TestCalculator.test_divide_by_zero_raises) ... ok
test_divide_normal (__main__.TestCalculator.test_divide_normal) ... ok
test_multiply_by_zero (__main__.TestCalculator.test_multiply_by_zero) ... ok
test_multiply_large_numbers (__main__.TestCalculator.test_multiply_large_numbers) ... ok
test_subtract (__main__.TestCalculator.test_subtract) ... ok
test_empty_dataset_raises (__main__.TestStatistics.test_empty_dataset_raises) ... ok
test_mean_normal_case (__main__.TestStatistics.test_mean_normal_case) ... ok
test_mean_single_value (__main__.TestStatistics.test_mean_single_value) ... ok
test_median_even_count (__main__.TestStatistics.test_median_even_count) ... ok
test_median_odd_count (__main__.TestStatistics.test_median_odd_count) ... ok
test_mode_single_mode (__main__.TestStatistics.test_mode_single_mode) ... ok
test_standard_deviation_single_value (__main__.TestStatistics.test_standard_deviation_single_value) ... ok

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Ran 14 tests in 0.000s

OK

  Tests run: 14
  Failures: 0
  Errors: 0
  All passed: True

--- Manual verification against Python's own statistics module ---
  Our mean:   5.5   |  stdlib mean:   5.5
  Our median: 5.5 |  stdlib median: 5.5
  Match: mean=True, median=True

--- Refactoring safety net demonstration ---
  (Refactored divide() to validate via a helper _check_nonzero(b) instead of
   an inline 'if b == 0' check -- re-running the exact same test suite below
   confirms behavior is unchanged.)
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Ran 2 tests in 0.000s

OK
  Refactored version still passes both tests: True
