I solved it but I don't understand the returns for short positions implied by the description and test cases. Say for example the case [1, 0.5]. If I sell $1000 worth of something short, then buy to cover at $500 I am now at $1500 which is 1.5x not 2.0x like in the test case. The maximum profit from a short position should be 100%.

Am I missing something?