Which pytest code correctly asserts this behavior and checks the error message?
hard📝 framework Q15 of 15
PyTest - Writing Assertions
You want to test a function parse_int(s) that should raise ValueError with message containing 'invalid literal' when given a non-integer string. Which pytest code correctly asserts this behavior and checks the error message?
Awith pytest.raises(ValueError):
parse_int('abc')
assert 'invalid literal' in e.value
Bpytest.raises(ValueError, parse_int('abc'))
assert 'invalid literal' in e.value
Cwith pytest.raises(ValueError) as e:
parse_int('abc')
assert 'invalid literal' in str(e.value)
Dwith pytest.raises('ValueError') as e:
parse_int('abc')
assert 'invalid literal' in str(e.value)
Step-by-Step Solution
Solution:
Step 1: Use correct syntax to capture exception info
Use with pytest.raises(ValueError) as e: to catch the exception and store info in e.
Step 2: Check error message properly
After the block, check if the string 'invalid literal' is in str(e.value). This converts the exception to string for message checking.
Step 3: Eliminate incorrect options
with pytest.raises(ValueError):
parse_int('abc')
assert 'invalid literal' in e.value tries to use e outside the block without capturing it. pytest.raises(ValueError, parse_int('abc'))
assert 'invalid literal' in e.value calls the function inside pytest.raises incorrectly and uses e undefined. with pytest.raises('ValueError') as e:
parse_int('abc')
assert 'invalid literal' in str(e.value) uses exception name as string instead of class.
Final Answer:
with pytest.raises(ValueError) as e:
parse_int('abc')
assert 'invalid literal' in str(e.value) -> Option C
Quick Check:
Capture exception with 'as' and check message string [OK]
Quick Trick:Use 'as' to capture exception and check message with str(e.value) [OK]
Common Mistakes:
MISTAKES
Using exception name as string instead of class
Calling function inside pytest.raises arguments
Accessing exception info outside 'with' without 'as'
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