Fix tests

Library/Homebrew/brew.rb

@@ -93,12 +93,14 @@ begin
     internal_cmd ||= begin
       internal_dev_cmd = Commands.valid_internal_dev_cmd?(cmd)
       if internal_dev_cmd && !Homebrew::EnvConfig.developer?
-        opoo <<~MESSAGE if ENV["HOMEBREW_DEV_CMD_RUN"].blank?
-          #{Tty.bold}#{cmd}#{Tty.reset} is a developer command, so
-          Homebrew's developer mode has been automatically turned on.
-          To turn developer mode off, run #{Tty.bold}brew developer off#{Tty.reset}
+        if ENV["HOMEBREW_DEV_CMD_RUN"].blank? && ENV["HOMEBREW_TEST"].blank?
+          opoo <<~MESSAGE
+            #{Tty.bold}#{cmd}#{Tty.reset} is a developer command, so
+            Homebrew's developer mode has been automatically turned on.
+            To turn developer mode off, run #{Tty.bold}brew developer off#{Tty.reset}
 
-        MESSAGE
+          MESSAGE
+        end
 
         Homebrew::Settings.write "devcmdrun", true
         ENV["HOMEBREW_DEV_CMD_RUN"] = "1"

Library/Homebrew/brew.sh

@@ -645,7 +645,7 @@ elif [[ -f "${HOMEBREW_LIBRARY}/Homebrew/dev-cmd/${HOMEBREW_COMMAND}.sh" ]]
 then
   if [[ -z "${HOMEBREW_DEVELOPER}" ]]
   then
-    if [[ -z "${HOMEBREW_DEV_CMD_RUN}" ]]
+    if [[ -z "${HOMEBREW_DEV_CMD_RUN}" ]] && [[ -z "${HOMEBREW_TEST}" ]]
     then
       message="$(bold "${HOMEBREW_COMMAND}") is a developer command, so
 Homebrew's developer mode has been automatically turned on.

Library/Homebrew/dev-cmd/tests.rb

@@ -87,6 +87,7 @@ module Homebrew
         ENV.delete(env)
       end
 
+      ENV["HOMEBREW_TEST"] = "1"
       ENV["HOMEBREW_NO_ANALYTICS_THIS_RUN"] = "1"
       ENV["HOMEBREW_NO_COMPAT"] = "1" if args.no_compat?
       ENV["HOMEBREW_TEST_GENERIC_OS"] = "1" if args.generic?