Migrate wrapper test to Cucumber.

test/features/step_definitions/completion.rb

@@ -4,10 +4,9 @@ require 'open3'
 
 module CompletionHelper
   def complete(cmd)
-    completions = run_fish_command("complete -C\"sdk #{cmd}\"")
+    completions = run_fish_command("complete -C\"sdk #{cmd}\"")[:stdout]
 
-    completions.split("\n") \
-               .map { |line| line.split(/\s+/)[0].strip }
+    completions.map { |line| line.split(/\s+/)[0].strip }
     # TODO: Why do we get duplicates in the Docker container?
   end
 end

test/features/step_definitions/wrapper.rb

@@ -0,0 +1,39 @@
+# frozen_string_literal: true
+
+module WrapperHelper
+  def reject_then_select(lines, exclude, select)
+    lines.select do |e|
+      (exclude.nil? || e !~ exclude) && e =~ select
+    end.sort
+  end
+
+  def compare_env(exclude, include)
+    env_bash = reject_then_select(@response_bash[:env], exclude, include)
+    env_fish = reject_then_select(@response_fish[:env], exclude, include)
+    expect(env_fish).to eq(env_bash)
+  end
+end
+World WrapperHelper
+
+When('we run {string} in Bash and Fish') do |command|
+  @response_bash = run_bash_command(command)
+  @response_fish = run_fish_command(command)
+end
+
+Then('the exit code is the same') do
+  expect(@response_fish[:status]).to eq(@response_bash[:status])
+end
+
+Then('the output is the same') do
+  %i[stdout stderr].each do |out|
+    expect(@response_fish[out]).to eq(@response_bash[out])
+  end
+end
+
+Then('environment variable(s) {env_glob} is/are the same') do |pattern|
+  compare_env(nil, pattern)
+end
+
+Then('environment variable(s) {env_glob} is/are the same except for {env_glob}') do |pattern, exclude_pattern|
+  compare_env(exclude_pattern, pattern)
+end