intro ldiff
case mpr
α : Program
ℓ ℓ' : TP α
⊢ (¬∀ τ ∈ (testsOfProgram α).attach, ℓ τ = ℓ' τ) → contradiction (signature α ℓ⋀signature α ℓ')
case mpr
α : Program
ℓ ℓ' : TP α
ldiff : ¬∀ τ ∈ (testsOfProgram α).attach, ℓ τ = ℓ' τ
⊢ contradiction (signature α ℓ⋀signature α ℓ')