How do I write test for homebrew formula? - testing

Question

I made an homebrew formula which is now accessible only on my local taps. I want to send pull request to homebrew-core. Now I am required to write test for my formula. How to write that based on example below?
test do
output = shell_output("#{bin}/balance 2>&1", 64)
assert_match "this is balance #{version}", output
end
My formula
#!/usr/bin/env ruby
def match
files = Dir.glob("*")
if ARGV.length == 0
puts "usage: match <keyword>"
return
end
files.each { |x|
if File.directory?(x)
puts "#{x}_ found directory"
puts "***"
next
end
found = false
File.open(x).each_line.with_index do |line, index|
if line.include? ARGV[0]
puts "#{x}_ #{index+1} #{line}"
found = true
end
end
puts "***" if found
}
end
match
Brew formula
class Match < Formula
desc "Browse all files inside any directory for a keyword"
homepage "https://github.com/aatalyk/homebrew-match"
url ""
sha256 ""
def install
bin.install "match"
end
end

Answer 1

Tests for shell commands in Homebrew formulae usually usually follow this scenario:
create a context usable by the command : a git repository, a directories hierarchy, a sample file, etc.
run the command
assert the result is correct
In your case since match is a grep -R -like you could create a bunch of files with some content, then run match <something> and ensure it finds the correct files.
You can use any Ruby code in your tests as well as Homebrew utilities such as shell_output("...command...") to get the output of a command.
Here is an example of test you could write:
class Match < Formula
# ...
test do
# Create two dummy files
(testpath/"file1").write "foo\nbar\nqux"
(testpath/"file2").write "bar\nabc"
# Ensure `match bar` finds both files
assert_match "file1_ 2 bar\n***\nfile2_ 1 bar",
shell_output("#{bin}/match bar")
# Ensure `match abc` finds the second file
assert_match "file2_ 2 abc", shell_output("#{bin}/match abc")
# Ensure `match idontmatchanything` doesn’t match any of the files
assert_not_match(/file[12]/,
shell_output("#{bin}/match idontmatchanything"))
end
end
assert_match "something", shell_output("command") ensures that (1) command runs successfully and (2) its output contains "something".