tests: add cmd/test integration test

Library/Homebrew/test/test_integration_cmds.rb

@@ -817,4 +817,31 @@ class IntegrationCommandTests < Homebrew::TestCase
     assert_match "testball does not have a version \"0.3\"",
       cmd_fail("switch", "testball", "0.3")
   end
+
+  def test_test_formula
+    assert_match "This command requires a formula argument", cmd_fail("test")
+    assert_match "Testing requires the latest version of testball",
+      cmd_fail("test", testball)
+
+    cmd("install", testball)
+    assert_match "testball defines no test", cmd_fail("test", testball)
+
+    setup_test_formula "testball_copy", <<-EOS.undent
+      head "https://github.com/example/testball2.git"
+
+      devel do
+        url "file://#{File.expand_path("..", __FILE__)}/tarballs/testball-0.1.tbz"
+        sha256 "#{TESTBALL_SHA256}"
+      end
+
+      keg_only "just because"
+
+      test do
+      end
+    EOS
+
+    cmd("install", "testball_copy")
+    assert_match "Testing testball_copy", cmd("test", "--HEAD", "testball_copy")
+    assert_match "Testing testball_copy", cmd("test", "--devel", "testball_copy")
+  end
 end