@testset "990.satisfiability-of-equality-equations.jl" begin
    @test equations_possible(["a==b", "b!=a"]) == false
    @test equations_possible(["b==a", "a==b"]) == true
    @test equations_possible(["a==b", "b==c", "a==c"]) == true
    @test equations_possible(["a==b", "b!=c", "c==a"]) == false
    @test equations_possible(["c==c", "b==d", "x!=z"]) == true
end