Shrink DependencyCollector#parse_symbol_spec and add tests

Library/Homebrew/dependency_collector.rb

@@ -76,13 +76,9 @@ private
     case spec
     when :autoconf, :automake, :bsdmake, :libtool
       # Xcode no longer provides autotools or some other build tools
-      Dependency.new(spec.to_s, [:build, *tag]) unless MacOS::Xcode.provides_autotools?
+      autotools_dep(spec, tag)
     when *X11Dependency::Proxy::PACKAGES
-      if MacOS.version >= :mountain_lion
+      x11_dep(spec, tag)
-        Dependency.new(spec.to_s, tag)
-      else
-        X11Dependency::Proxy.for(spec.to_s, tag)
-      end
     when :cairo, :pixman
       # We no longer use X11 psuedo-deps for cairo or pixman,
       # so just return a standard formula dependency.
@@ -97,4 +93,18 @@ private
       raise "Unsupported special dependency #{spec}"
     end
   end
+
+  def x11_dep(spec, tag)
+    if MacOS.version >= :mountain_lion
+      Dependency.new(spec.to_s, tag)
+    else
+      X11Dependency::Proxy.for(spec.to_s, tag)
+    end
+  end
+
+  def autotools_dep(spec, tag)
+    unless MacOS::Xcode.provides_autotools?
+      Dependency.new(spec.to_s, [:build, *tag])
+    end
+  end
 end

Library/Homebrew/test/test_dependency_collector.rb

@@ -81,6 +81,28 @@ class DependencyCollectorTests < Test::Unit::TestCase
     assert_equal '2.5.1', dep.min_version
     assert dep.optional?
   end
+
+  def test_autotools_dep_no_system_autotools
+    MacOS::Xcode.stubs(:provides_autotools?).returns(false)
+    dep = @d.build(:libtool)
+    assert_equal Dependency.new("libtool"), dep
+    assert dep.build?
+  end
+
+  def test_autotools_dep_system_autotools
+    MacOS::Xcode.stubs(:provides_autotools?).returns(true)
+    assert_nil @d.build(:libtool)
+  end
+
+  def test_x11_proxy_dep_mountain_lion
+    MacOS.stubs(:version).returns(MacOS::Version.new(10.8))
+    assert_equal Dependency.new("libpng"), @d.build(:libpng)
+  end
+
+  def test_x11_proxy_dep_lion_or_older
+    MacOS.stubs(:version).returns(MacOS::Version.new(10.7))
+    assert_equal X11Dependency::Proxy.new(:libpng), @d.build(:libpng)
+  end
 end
 
 class LanguageModuleDependencyTests < Test::Unit::TestCase