def test_peek_returns_next_opcode_without_changing_code_stream_location():
code_stream = CodeStream(b'\x01\x02\x30')
assert code_stream.pc == 0
assert code_stream.peek() == opcode_values.ADD
assert code_stream.pc == 0
assert next(code_stream) == opcode_values.ADD
assert code_stream.pc == 1
assert code_stream.peek() == opcode_values.MUL
assert code_stream.pc == 1
def test_seek_reverts_to_original_stream_position_when_context_exits():
code_stream = CodeStream(b'\x01\x02\x30')
assert code_stream.pc == 0
with code_stream.seek(1):
assert code_stream.pc == 1
assert next(code_stream) == opcode_values.MUL
assert code_stream.pc == 0
assert code_stream.peek() == opcode_values.ADD
