intro ℓ_eq_ℓ _ _
case mp
α : Program
ℓ ℓ' : TP α
⊢ ℓ = ℓ' → ∀ τ ∈ (testsOfProgram α).attach, ℓ τ = ℓ' τ
case mp
α : Program
ℓ ℓ' : TP α
ℓ_eq_ℓ : ℓ = ℓ'
τ✝ : { x // x ∈ testsOfProgram α }
a✝ : τ✝ ∈ (testsOfProgram α).attach
⊢ ℓ τ✝ = ℓ' τ✝