test_bash: tests to assert Bash syntax is valid.

Closes Homebrew/homebrew#47380.

Library/Homebrew/test/test_bash.rb

@@ -0,0 +1,16 @@
+require "testing_env"
+
+class BashTests < Homebrew::TestCase
+  def assert_valid_bash_syntax(files)
+    output = Utils.popen_read("/bin/bash -n #{files} 2>&1")
+    assert $?.success?, output
+  end
+
+  def test_bin_brew
+    assert_valid_bash_syntax "#{HOMEBREW_LIBRARY_PATH.parent.parent}/bin/brew"
+  end
+
+  def test_bash_cmds
+    assert_valid_bash_syntax "#{HOMEBREW_LIBRARY_PATH}/cmd/*.sh"
+  end
+end