diff --git a/Library/Homebrew/diagnostic.rb b/Library/Homebrew/diagnostic.rb
index 4954cde7b7..62f63b34f0 100644
--- a/Library/Homebrew/diagnostic.rb
+++ b/Library/Homebrew/diagnostic.rb
@@ -96,7 +96,7 @@ module Homebrew
 
         <<-EOS.undent
           No developer tools installed.
-          Install clang or gcc.
+          #{DevelopmentTools.installation_instructions}
         EOS
       end
 
diff --git a/Library/Homebrew/extend/os/mac/diagnostic.rb b/Library/Homebrew/extend/os/mac/diagnostic.rb
index 739c8018f3..120e5d15cf 100644
--- a/Library/Homebrew/extend/os/mac/diagnostic.rb
+++ b/Library/Homebrew/extend/os/mac/diagnostic.rb
@@ -48,104 +48,23 @@ module Homebrew
         EOS
       end
 
-      # TODO: distill down into single method definition a la BuildToolsError
-      if MacOS.version >= "10.9"
-        def check_for_installed_developer_tools
-          return if MacOS::Xcode.installed? || MacOS::CLT.installed?
+      def check_xcode_up_to_date
+        return unless MacOS::Xcode.installed? && MacOS::Xcode.outdated?
 
-          <<-EOS.undent
-            No developer tools installed.
-            Install the Command Line Tools:
-              xcode-select --install
-          EOS
-        end
+        <<-EOS.undent
+          Your Xcode (#{MacOS::Xcode.version}) is outdated
+          Please update to Xcode #{MacOS::Xcode.latest_version}.
+          #{MacOS::Xcode.update_instructions}
+        EOS
+      end
 
-        if OS::Mac.prerelease?
-          def check_xcode_up_to_date
-            return unless MacOS::Xcode.installed? && MacOS::Xcode.outdated?
+      def check_clt_up_to_date
+        return unless MacOS::CLT.installed? && MacOS::CLT.outdated?
 
-            <<-EOS.undent
-              Your Xcode (#{MacOS::Xcode.version}) is outdated
-              Please update to Xcode #{MacOS::Xcode.latest_version}.
-              Xcode can be updated from
-                https://developer.apple.com/xcode/downloads/
-            EOS
-          end
-        else
-          def check_xcode_up_to_date
-            return unless MacOS::Xcode.installed? && MacOS::Xcode.outdated?
-
-            <<-EOS.undent
-              Your Xcode (#{MacOS::Xcode.version}) is outdated
-              Please update to Xcode #{MacOS::Xcode.latest_version}.
-              Xcode can be updated from the App Store.
-            EOS
-          end
-        end
-
-        def check_clt_up_to_date
-          return unless MacOS::CLT.installed? && MacOS::CLT.outdated?
-
-          <<-EOS.undent
-            A newer Command Line Tools release is available.
-            Update them from Software Update in the App Store.
-          EOS
-        end
-      elsif MacOS.version == "10.8" || MacOS.version == "10.7"
-        def check_for_installed_developer_tools
-          return if MacOS::Xcode.installed? || MacOS::CLT.installed?
-
-          <<-EOS.undent
-            No developer tools installed.
-            You should install the Command Line Tools.
-            The standalone package can be obtained from
-              https://developer.apple.com/downloads
-            or it can be installed via Xcode's preferences.
-          EOS
-        end
-
-        def check_xcode_up_to_date
-          return unless MacOS::Xcode.installed? && MacOS::Xcode.outdated?
-
-          <<-EOS.undent
-            Your Xcode (#{MacOS::Xcode.version}) is outdated
-            Please update to Xcode #{MacOS::Xcode.latest_version}.
-            Xcode can be updated from
-              https://developer.apple.com/xcode/downloads/
-          EOS
-        end
-
-        def check_clt_up_to_date
-          return unless MacOS::CLT.installed? && MacOS::CLT.outdated?
-
-          <<-EOS.undent
-            A newer Command Line Tools release is available.
-            The standalone package can be obtained from
-              https://developer.apple.com/downloads
-            or it can be installed via Xcode's preferences.
-          EOS
-        end
-      else
-        def check_for_installed_developer_tools
-          return if MacOS::Xcode.installed?
-
-          <<-EOS.undent
-            Xcode is not installed. Most formulae need Xcode to build.
-            It can be installed from
-              https://developer.apple.com/xcode/downloads/
-          EOS
-        end
-
-        def check_xcode_up_to_date
-          return unless MacOS::Xcode.installed? && MacOS::Xcode.outdated?
-
-          <<-EOS.undent
-            Your Xcode (#{MacOS::Xcode.version}) is outdated
-            Please update to Xcode #{MacOS::Xcode.latest_version}.
-            Xcode can be updated from
-              https://developer.apple.com/xcode/downloads/
-          EOS
-        end
+        <<-EOS.undent
+          A newer Command Line Tools release is available.
+          #{MacOS::CLT.update_instructions}
+        EOS
       end
 
       def check_for_osx_gcc_installer
diff --git a/Library/Homebrew/test/test_diagnostic.rb b/Library/Homebrew/test/test_diagnostic.rb
index 0e0d110e7e..2974b05902 100644
--- a/Library/Homebrew/test/test_diagnostic.rb
+++ b/Library/Homebrew/test/test_diagnostic.rb
@@ -44,19 +44,6 @@ class DiagnosticChecksTest < Homebrew::TestCase
     end
   end
 
-  def test_check_for_other_package_managers
-    MacOS.stubs(:macports_or_fink).returns ["fink"]
-    assert_match "You have MacPorts or Fink installed:",
-      @checks.check_for_other_package_managers
-  end
-
-  def test_check_for_unsupported_osx
-    ARGV.stubs(:homebrew_developer?).returns false
-    OS::Mac.stubs(:prerelease?).returns true
-    assert_match "We do not provide support for this pre-release version.",
-      @checks.check_for_unsupported_osx
-  end
-
   def test_check_access_homebrew_repository
     mod = HOMEBREW_REPOSITORY.stat.mode & 0777
     HOMEBREW_REPOSITORY.chmod 0555
@@ -163,14 +150,6 @@ class DiagnosticChecksTest < Homebrew::TestCase
     end
   end
 
-  def test_check_for_unsupported_curl_vars
-    MacOS.stubs(:version).returns OS::Mac::Version.new("10.10")
-    ENV["SSL_CERT_DIR"] = "/some/path"
-
-    assert_match "SSL_CERT_DIR support was removed from Apple's curl.",
-      @checks.check_for_unsupported_curl_vars
-  end
-
   def test_check_for_config_scripts
     mktmpdir do |path|
       file = "#{path}/foo-config"
@@ -226,9 +205,4 @@ class DiagnosticChecksTest < Homebrew::TestCase
       end
     end
   end
-
-  def test_check_for_beta_xquartz
-    MacOS::XQuartz.stubs(:version).returns("2.7.10_beta2")
-    assert_match "The following beta release of XQuartz is installed: 2.7.10_beta2", @checks.check_for_beta_xquartz
-  end
 end
diff --git a/Library/Homebrew/test/test_os_mac_diagnostic.rb b/Library/Homebrew/test/test_os_mac_diagnostic.rb
new file mode 100644
index 0000000000..a52179ac6f
--- /dev/null
+++ b/Library/Homebrew/test/test_os_mac_diagnostic.rb
@@ -0,0 +1,41 @@
+require "testing_env"
+require "fileutils"
+require "pathname"
+require "diagnostic"
+
+class OSMacDiagnosticChecksTest < Homebrew::TestCase
+  def setup
+    @env = ENV.to_hash
+    @checks = Homebrew::Diagnostic::Checks.new
+  end
+
+  def teardown
+    ENV.replace(@env)
+  end
+
+  def test_check_for_other_package_managers
+    MacOS.stubs(:macports_or_fink).returns ["fink"]
+    assert_match "You have MacPorts or Fink installed:",
+      @checks.check_for_other_package_managers
+  end
+
+  def test_check_for_unsupported_osx
+    ARGV.stubs(:homebrew_developer?).returns false
+    OS::Mac.stubs(:prerelease?).returns true
+    assert_match "We do not provide support for this pre-release version.",
+      @checks.check_for_unsupported_osx
+  end
+
+  def test_check_for_unsupported_curl_vars
+    MacOS.stubs(:version).returns OS::Mac::Version.new("10.10")
+    ENV["SSL_CERT_DIR"] = "/some/path"
+
+    assert_match "SSL_CERT_DIR support was removed from Apple's curl.",
+      @checks.check_for_unsupported_curl_vars
+  end
+
+  def test_check_for_beta_xquartz
+    MacOS::XQuartz.stubs(:version).returns("2.7.10_beta2")
+    assert_match "The following beta release of XQuartz is installed: 2.7.10_beta2", @checks.check_for_beta_xquartz
+  end
+end