Stubbing on the command line.

test_example

#!/bin/sh

cat > example <<"DOC"
#!/usr/bin/env ruby
puts "got: #{`git log | head -n 1`}"
DOC
chmod +x example

test_example () {
./example | grep "got: commit [[:xdigit:]]\{40\}"
}

test_example_with_stub () {
git () {
  echo abc
}
export -f git
./example | assert_output "\
got: abc
"
}

. ts