Create minitest template file

Supports the same tests as rspec template

README.md

@@ -39,6 +39,12 @@ Copy rspec test to test for missing and unused translations as part of the suite
 $ cp $(i18n-tasks gem-path)/templates/rspec/i18n_spec.rb spec/
 ```
 
+Or for minitest:
+
+```console
+$ cp $(i18n-tasks gem-path)/templates/minitest/i18n_test.rb test/
+```
+
 ## Usage
 
 Run `i18n-tasks` to get the list of all the tasks with short descriptions.

templates/minitest/i18n_test.rb

@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+require 'i18n/tasks'
+
+class I18nTest < ActiveSupport::TestCase
+  def setup
+    @i18n = I18n::Tasks::BaseTask.new
+    @missing_keys = @i18n.missing_keys
+    @unused_keys = @i18n.unused_keys
+  end
+
+  def test_no_missing_keys
+    assert_empty @missing_keys,
+                 "Missing #{@missing_keys.leaves.count} i18n keys, run `i18n-tasks missing' to show them"
+  end
+
+  def test_no_unused_keys
+    assert_empty @unused_keys,
+                 "#{@unused_keys.leaves.count} unused i18n keys, run `i18n-tasks unused' to show them"
+  end
+end