test_gpg2_requirement: add satisfied test

Library/Homebrew/test/test_gpg2_requirement.rb

+require "testing_env"
+require "requirements/gpg2_requirement"
+require "fileutils"
+
+class GPG2RequirementTests < Homebrew::TestCase
+  def setup
+    @dir = Pathname.new(mktmpdir)
+    (@dir/"bin/gpg").write <<-EOS.undent
+      #!/bin/bash
+      echo 2.0.30
+    EOS
+    FileUtils.chmod 0755, @dir/"bin/gpg"
+  end
+
+  def teardown
+    FileUtils.rm_rf @dir
+  end
+
+  def test_satisfied
+    with_environment("PATH" => @dir/"bin") do
+      assert_predicate GPG2Requirement.new, :satisfied?
+    end
+  end
+end