req.Header.Del("Authorization")
		}
		switch testCase.fault {
		case malformedEncoding:
			req, err = malformChunkSizeSigV4(req, testCase.chunkSize-1)
		case signatureMismatch:
			req, err = malformDataSigV4(req, 'z')
		case unexpectedEOF:
			req, err = truncateChunkByHalfSigv4(req)
		case tooBigDecodedLength:
			// Set decoded length to a large value out of int64 range to simulate parse failure.