def test_env_add():
skx = SymbolicKeyInstance("x", 1)
sky = SymbolicKeyInstance("y", 2)
ex = newenv.set(skx, 10)
ey = newenv.set(sky, 20)
exy = newenv.set(skx, 7).set(sky, 8)
new = ex.add(ey)
assert new.get(skx, 0) == 10
assert new.get(sky, 0) == 20
new = ey.add(ex)
assert new.get(skx, 0) == 10
assert new.get(sky, 0) == 20
new = exy.add(ex)
assert new.get(skx, 0) == 17
assert new.get(sky, 0) == 8
def test_env():
sk1 = SymbolicKeyInstance('x', {})
sk1b = SymbolicKeyInstance('x', {})
assert sk1 == sk1b
sk2 = SymbolicKeyInstance('y', {})
e = newenv.set(sk1, 100)
assert e is not newenv
assert len(newenv) == 0
assert len(e) == 1
assert e.get(sk1, 0) == 100
assert e.get(sk2, 0) == 0
e = e.set(sk1b, 200)
assert len(e) == 1
assert e.get(sk1, 0) == 200
assert e.get(sk2, 0) == 0
e = e.set(sk2, 300)
assert len(e) == 2
assert e.get(sk1, 0) == 200
assert e.get(sk2, 0) == 300