DeMorgan's Law

if ! found_x && ! found_y; then
  # FAIL
fi

if !(found_x || found_y); then
  # FAIL
fi

Rule

• NOT(A AND B)
  • NOT(A) OR NOT(B)
• NOT(A OR B)
  • NOT(A) AND NOT(B)

Implications

When neither A nor B is FALSE, A AND B condition cannot be met

• Only when A is FALSE AND B is also FALSE, A OR B will be FALSE