vader.vim is easy, and amazing. It has no external dependencies (doesn't require ruby/rake), it's a pure vimscript plugin. Here's a fully specified test:
Given (description of test):
foo bar baz
Do (move around, insert some text):
2Wiab<Enter>c
Expect:
foo bar ab
cbaz
If you have the test file open, you can run it like this:
:Vader %
Or you can point to the file path:
:Vader ./test.vader
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