image/gif: make test repeatable

Fixes issue with go test -cpu=1,1

R=minux.ma, bradfitz, nigeltao
CC=golang-dev
https://golang.org/cl/7808045

diff --git a/src/pkg/image/gif/reader_test.go b/src/pkg/image/gif/reader_test.go
index a035ef1ea5175e3aa61430e89d3f36eb8ec81f8d..dcc6c6dd3e45937a072ee4755f85d3edabb64a31 100644 (file)
--- a/src/pkg/image/gif/reader_test.go
+++ b/src/pkg/image/gif/reader_test.go
@@ -114,22 +114,25 @@ func try(t *testing.T, b []byte, want string) {
 }
 
 func TestBounds(t *testing.T) {
+       // make a local copy of testGIF
+       gif := make([]byte, len(testGIF))
+       copy(gif, testGIF)
        // Make the bounds too big, just by one.
-       testGIF[32] = 2
+       gif[32] = 2
        want := "gif: frame bounds larger than image bounds"
-       try(t, testGIF, want)
+       try(t, gif, want)
 
        // Make the bounds too small; does not trigger bounds
        // check, but now there's too much data.
-       testGIF[32] = 0
+       gif[32] = 0
        want = "gif: too much image data"
-       try(t, testGIF, want)
-       testGIF[32] = 1
+       try(t, gif, want)
+       gif[32] = 1
 
        // Make the bounds really big, expect an error.
        want = "gif: frame bounds larger than image bounds"
        for i := 0; i < 4; i++ {
-               testGIF[32+i] = 0xff
+               gif[32+i] = 0xff
        }
-       try(t, testGIF, want)
+       try(t, gif, want)
 }