def test_FracElement():
    Fuv, u,v = field("u,v", ZZ);
    Fxyzt, x,y,z,t = field("x,y,z,t", Fuv.to_domain())

    assert str(x - x) == "0"
    assert str(x - 1) == "x - 1"
    assert str(x + 1) == "x + 1"

    assert str(x/z) == "x/z"
    assert str(x*y/z) == "x*y/z"
    assert str(x/(z*t)) == "x/(z*t)"
    assert str(x*y/(z*t)) == "x*y/(z*t)"

    assert str((x - 1)/y) == "(x - 1)/y"
    assert str((x + 1)/y) == "(x + 1)/y"
    assert str((-x - 1)/y) == "(-x - 1)/y"
    assert str((x + 1)/(y*z)) == "(x + 1)/(y*z)"
    assert str(-y/(x + 1)) == "-y/(x + 1)"
    assert str(y*z/(x + 1)) == "y*z/(x + 1)"

    assert str(((u + 1)*x*y + 1)/((v - 1)*z - 1)) == "((u + 1)*x*y + 1)/((v - 1)*z - 1)"
    assert str(((u + 1)*x*y + 1)/((v - 1)*z - t*u*v - 1)) == "((u + 1)*x*y + 1)/((v - 1)*z - u*v*t - 1)"

def test_FracField():
    assert str(field("x", ZZ, lex)[0]) == "Rational function field in x over ZZ with lex order"
    assert str(field("x,y", QQ, grlex)[0]) == "Rational function field in x, y over QQ with grlex order"
    assert str(field("x,y,z", ZZ["t"], lex)[0]) == "Rational function field in x, y, z over ZZ[t] with lex order"

def test_FracElement():
    F, x, y = field("x,y", ZZ)
    assert srepr((3*x**2*y + 1)/(x - y**2)) == "FracElement(FracField((Symbol('x'), Symbol('y')), ZZ, lex), [((2, 1), 3), ((0, 0), 1)], [((1, 0), 1), ((0, 2), -1)])"

def test_FracField():
    assert srepr(field("x", ZZ, lex)[0]) == "FracField((Symbol('x'),), ZZ, lex)"
    assert srepr(field("x,y", QQ, grlex)[0]) == "FracField((Symbol('x'), Symbol('y')), QQ, grlex)"
    assert srepr(field("x,y,z", ZZ["t"], lex)[0]) == "FracField((Symbol('x'), Symbol('y'), Symbol('z')), ZZ[t], lex)"