mysql@5.6: don't retain huge test folder, replace existing test

Formula/mysql@5.6.rb

@@ -101,6 +101,12 @@ class MysqlAT56 < Formula
     system "make"
     system "make", "install"
 
+    # We don't want to keep a 240MB+ folder around most users won't need.
+    (prefix/"mysql-test").cd do
+      system "./mysql-test-run.pl", "status", "--vardir=#{Dir.mktmpdir}"
+    end
+    rm_rf prefix/"mysql-test"
+
     # Don't create databases inside of the prefix!
     # See: https://github.com/Homebrew/homebrew/issues/4975
     rm_rf prefix/"data"
@@ -167,9 +173,23 @@ class MysqlAT56 < Formula
   end
 
   test do
-    system "/bin/sh", "-n", "#{bin}/mysqld_safe"
-    (prefix/"mysql-test").cd do
-      system "./mysql-test-run.pl", "status", "--vardir=#{testpath}"
+    begin
+      # Expects datadir to be a completely clean dir, which testpath isn't.
+      dir = Dir.mktmpdir
+      system bin/"mysql_install_db", "--user=#{ENV["USER"]}",
+      "--basedir=#{prefix}", "--datadir=#{dir}", "--tmpdir=#{dir}"
+
+      pid = fork do
+        exec bin/"mysqld", "--bind-address=127.0.0.1", "--datadir=#{dir}"
+      end
+      sleep 2
+
+      output = shell_output("curl 127.0.0.1:3306")
+      output.force_encoding("ASCII-8BIT") if output.respond_to?(:force_encoding)
+      assert_match version.to_s, output
+    ensure
+      Process.kill(9, pid)
+      Process.wait(pid)
     end
   end
 end