Why test?

301.13 Testing

Testing — Note 1 of 6

Purpose of software testing.

What you need to know

Testing checks that a program works correctly under different conditions. Without testing, bugs can go unnoticed and cause incorrect results or crashes.

What to know

Testing finds errors before users do
Test with a range of inputs, not just obvious ones
Even code that 'looks right' can have logic errors
Testing should be systematic, not random

Code examples

Untested bug example

python

# This looks correct but fails for negative numbers
def is_even(n):
    return n % 2 == 0

print(is_even(4))   # True ✓
print(is_even(-3))  # False ✓
# Always test edge cases!

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Specification notes for programming are in Paper 2.