fixtures: add Open() function

Adds a method for streaming fixture files

fixtures/fixtures.go

@@ -11,7 +11,7 @@ import (
 )
 
 // Path returns the absolute path for the fixture at the given relative path.
-func Path(t *testing.T, strs ...string) string {
+func Path(t testing.TB, strs ...string) string {
 	_, file, _, ok := runtime.Caller(0)
 	require.True(t, ok, "runtime.Caller failed")
 	parts := make([]string, 1, 1+len(strs))
@@ -21,8 +21,15 @@ func Path(t *testing.T, strs ...string) string {
 }
 
 // Load returns the fixture at the given path.
-func Load(t *testing.T, strs ...string) []byte {
+func Load(t testing.TB, strs ...string) []byte {
 	data, err := os.ReadFile(Path(t, strs...))
 	require.NoError(t, err)
 	return data
 }
+
+// Open returns a file handle for a fixture.
+func Open(t testing.TB, strs ...string) *os.File {
+	f, err := os.Open(Path(t, strs...))
+	require.NoError(t, err)
+	return f
+}