Provide a method to access test fixtures

Formulae should not require knowledge of Homebrew's internal directory
structure, and we should be able to alter it without modifying
individual formulae.

Formula/dnsrend.rb

@@ -42,7 +42,6 @@ class Dnsrend < Formula
   end
 
   test do
-    test_pcap = HOMEBREW_LIBRARY/"Homebrew/test/fixtures/test.pcap"
-    system "#{bin}/dnsrend", test_pcap
+    system "#{bin}/dnsrend", test_fixtures("test.pcap")
   end
 end

Formula/gd.rb

@@ -74,8 +74,7 @@ class Gd < Formula
   end
 
   test do
-    test_png = HOMEBREW_LIBRARY/"Homebrew/test/fixtures/test.png"
-    system "#{bin}/pngtogd", test_png, "gd_test.gd"
+    system "#{bin}/pngtogd", test_fixtures("test.png"), "gd_test.gd"
     system "#{bin}/gdtopng", "gd_test.gd", "gd_test.png"
   end
 end

Formula/graphicsmagick.rb

@@ -88,8 +88,7 @@ class Graphicsmagick < Formula
   end
 
   test do
-    test_png = HOMEBREW_LIBRARY/"Homebrew/test/fixtures/test.png"
-    system "#{bin}/gm", "identify", test_png
+    system "#{bin}/gm", "identify", test_fixtures("test.png")
   end
 
   def caveats

Formula/hachoir-metadata.rb

@@ -45,8 +45,7 @@ class HachoirMetadata < Formula
   end
 
   test do
-    test_png = HOMEBREW_LIBRARY/"Homebrew/test/fixtures/test.png"
-    output = `#{bin}/hachoir-metadata --mime #{test_png}`
+    output = `#{bin}/hachoir-metadata --mime #{test_fixtures("test.png")}`
     assert output.include?("image/png")
     assert_equal 0, $?.exitstatus
   end

Formula/imagemagick.rb

@@ -116,7 +116,6 @@ class Imagemagick < Formula
   end
 
   test do
-    test_png = HOMEBREW_LIBRARY/"Homebrew/test/fixtures/test.png"
-    system "#{bin}/identify", test_png
+    system "#{bin}/identify", test_fixtures("test.png")
   end
 end

Formula/imlib2.rb

@@ -33,7 +33,6 @@ class Imlib2 < Formula
   end
 
   test do
-    test_png = HOMEBREW_LIBRARY/"Homebrew/test/fixtures/test.png"
-    system "#{bin}/imlib2_conv", test_png, "imlib2_test.png"
+    system "#{bin}/imlib2_conv", test_fixtures("test.png"), "imlib2_test.png"
   end
 end

Formula/jpeg-turbo.rb

@@ -26,10 +26,9 @@ class JpegTurbo < Formula
   end
 
   test do
-    test_jpg = HOMEBREW_LIBRARY/"Homebrew/test/fixtures/test.jpg"
     system "#{bin}/jpegtran", "-crop", "1x1",
                               "-transpose", "-perfect",
                               "-outfile", "out.jpg",
-                              test_jpg
+                              test_fixtures("test.jpg")
   end
 end

Formula/mozjpeg.rb

@@ -30,10 +30,9 @@ class Mozjpeg < Formula
   end
 
   test do
-    test_jpg = HOMEBREW_LIBRARY/"Homebrew/test/fixtures/test.jpg"
     system "#{bin}/jpegtran", "-crop", "1x1",
                               "-transpose", "-optimize",
                               "-outfile", "out.jpg",
-                              test_jpg
+                              test_fixtures("test.jpg")
   end
 end

Formula/ndpi.rb

@@ -25,7 +25,6 @@ class Ndpi < Formula
   end
 
   test do
-    test_pcap = HOMEBREW_LIBRARY/"Homebrew/test/fixtures/test.pcap"
-    system "#{bin}/ndpiReader", "-i", test_pcap
+    system "#{bin}/ndpiReader", "-i", test_fixtures("test.pcap")
   end
 end

Formula/p0f.rb

@@ -20,7 +20,6 @@ class P0f < Formula
   end
 
   test do
-    test_pcap = HOMEBREW_LIBRARY/"Homebrew/test/fixtures/test.pcap"
-    system "#{sbin}/p0f", "-r", test_pcap
+    system "#{sbin}/p0f", "-r", test_fixtures("test.pcap")
   end
 end

Formula/swftools.rb

@@ -32,8 +32,7 @@ class Swftools < Formula
   end
 
   test do
-    test_png = HOMEBREW_LIBRARY/"Homebrew/test/fixtures/test.png"
-    system "#{bin}/png2swf", "swftools_test.swf", test_png
+    system "#{bin}/png2swf", "swftools_test.swf", test_fixtures("test.png")
   end
 end
 

Formula/tiff2png.rb

@@ -25,8 +25,7 @@ class Tiff2png < Formula
   end
 
   test do
-    test_tiff = HOMEBREW_LIBRARY/"Homebrew/test/fixtures/test.tiff"
-    system "#{bin}/tiff2png", test_tiff
+    system "#{bin}/tiff2png", test_fixtures("test.tiff")
   end
 end
 

Formula/webp.rb

@@ -33,8 +33,7 @@ class Webp < Formula
   end
 
   test do
-    test_png = HOMEBREW_LIBRARY/"Homebrew/test/fixtures/test.png"
-    system "#{bin}/cwebp", test_png, "-o", "webp_test.png"
+    system "#{bin}/cwebp", test_fixtures("test.png"), "-o", "webp_test.png"
     system "#{bin}/dwebp", "webp_test.png", "-o", "webp_test.webp"
   end
 end