Remove Invalid Pack test for ioutil.Discard (#241)

The internal definition of ioutil.Discard is not stable, so we should
not be testing packing with such a value.

Also, the `testEncodingInvalidSlices` function is only used in a
single place, so I just moved its implementation into
`TestEncodingPackTypeInvalid`.

Signed-off-by: Joe Richey <[email protected]>

tpmutil/encoding_test.go

@@ -27,40 +27,28 @@ type invalidPacked struct {
 	B uint32
 }
 
-func testEncodingInvalidSlices(t *testing.T, f func(io.Writer, interface{}) error) {
+func TestEncodingPackTypeInvalid(t *testing.T) {
 	d := ioutil.Discard
 
 	// The packedSize function doesn't handle slices to anything other than bytes.
 	var invalid []int
-	if err := f(d, invalid); err == nil {
+	if err := packType(d, invalid); err == nil {
 		t.Fatal("The packing function incorrectly succeeds for a slice of integers")
 	}
-	if err := f(d, &invalid); err == nil {
+	if err := packType(d, &invalid); err == nil {
 		t.Fatal("The packing function incorrectly succeeds for a pointer to a slice of integers")
 	}
 
 	invalid2 := invalidPacked{
 		A: make([]int, 10),
 		B: 137,
 	}
-	if err := f(d, invalid2); err == nil {
+	if err := packType(d, invalid2); err == nil {
 		t.Fatal("The packing function incorrectly succeeds for a struct that contains an integer slice")
 	}
-	if err := f(d, &invalid2); err == nil {
+	if err := packType(d, &invalid2); err == nil {
 		t.Fatal("The packing function incorrectly succeeds for a pointer to a struct that contains an integer slice")
 	}
-
-	if err := f(d, d); err == nil {
-		t.Fatal("The packing function incorrectly succeeds for a non-packable value")
-	}
-}
-
-func TestEncodingPackTypeInvalid(t *testing.T) {
-	f := func(w io.Writer, i interface{}) error {
-		return packType(w, i)
-	}
-
-	testEncodingInvalidSlices(t, f)
 }
 
 type simplePacked struct {