I am using simplecov for code coverage. I have no idea what sequence coverage is. I Googled it but I could not find anything, although I did find information about Branch Coverage.
The term "Sequence coverage" comes from Shippable CI, not simplecov.
From Shippable's API documentation we can find this:
branchCoveragePercent The percentage of branches (if/then/else condtions) that are covered by tests
sequenceCoveragePercent Percentage of lines there are code coverage for
So branch coverage counts all your code branching such as:
if a==b
do stuff # branch 1
else
do other stuff # branch 2
end
Now if your test suite only tests when a==b, your branch coverage for this file is 50%.
Sequence coverage is the regular line by line coverage report, if your code has 100 lines and during the tests only 70% of the lines have been run, your sequence coverage is 70%.