DonchianChannel tests don't catch errors with Donchian Channels 50 Mean

Expected Behavior

If calculated mean value is different from "Donchian Channels 50 Mean" column value from spy_with_don50.txt file, test ComparesAgainstExternalData should fail which is not the case currently.

Actual Behavior

Change values in spy_with_don50.txt file from

Date,Open,High,Low,Close,Donchian Channels 50 Top,Donchian Channels 50 Bottom,Donchian Channels 50 Mean
3/15/2013 12:00:00 AM,155.85,156.04,155.31,155.83,156.04,155.31,155.675

to

Date,Open,High,Low,Close,Donchian Channels 50 Top,Donchian Channels 50 Bottom,Donchian Channels 50 Mean
3/15/2013 12:00:00 AM,155.85,156.04,155.31,155.83,156.04,155.31,999155.675

run DonchianChannelTests... it should fail... but doesn't

Potential Solution

Consider something like #8162 for indicators with several outputs ie give an array of columns to read (from reference data) and an array of assertion functions.

Reproducing the Problem

see previously

System Information

Checklist

• I have completely filled out this template
• I have confirmed that this issue exists on the current master branch
• I have confirmed that this is not a duplicate issue by searching issues

• I have provided detailed steps to reproduce the issue

Start with DonchianChannelTests and the spy_with_don50.txt reference data, especially the ComparesAgainstExternalData test. Run the DonchianChannelTests after changing the Donchian Channels 50 Mean value to confirm the current test still passes. Done means the test detects a mismatched mean value and fails appropriately.