assert: simplify Contains logic for byte slice

assert/assertions.go

@@ -906,12 +906,11 @@ func containsElement(list interface{}, element interface{}) (ok, found bool) {
 		}
 		return true, false
 	case reflect.Slice:
-		// Special case: use bytes.Contains if both element and list are []byte.
-		elementValue := reflect.ValueOf(element)
-		if elementValue.Kind() == reflect.Slice &&
-			elementValue.Type().Elem().Kind() == reflect.Uint8 &&
-			listType.Elem().Kind() == reflect.Uint8 {
-			return true, bytes.Contains(listValue.Bytes(), elementValue.Bytes())
+		switch element := element.(type) {
+		case []byte:
+		    if list, ok := list.([]byte); ok {
+			return true, bytes.Contains(list, element)
+		    }
 		}
 	}
 

assert/assertions_test.go

@@ -922,15 +922,18 @@ func TestContainsNotContains(t *testing.T) {
 	}
 	list := []string{"Hello", "World"}
 
+	byteSliceList := [][]byte{
+		[]byte("Hello"), []byte("World"),
+	}
+
 	complexList := []*A{
 		{"b", "c"},
 		{"d", "e"},
 		{"g", "h"},
 		{"j", "k"},
 	}
-	byteSliceList := [][]byte{
-		[]byte("Hello"), []byte("World"),
-	}
+
+	interfaceList := []interface{}{"Hello World", 5, 2, []byte("Goodbye")}
 
 	simpleMap := map[interface{}]interface{}{"Hello": "World"}
 	var zeroMap map[interface{}]interface{}
@@ -950,6 +953,9 @@ func TestContainsNotContains(t *testing.T) {
 		{byteSliceList, []byte("Earth"), false},
 		{complexList, &A{"g", "h"}, true},
 		{complexList, &A{"g", "e"}, false},
+		{interfaceList, 5, true},
+		{interfaceList, []byte("Goodbye"), true},
+		{interfaceList, "World", false},
 		{simpleMap, "Hello", true},
 		{simpleMap, "Earth", false},
 		{zeroMap, "Bar", false},