Use assert for test (#3201)

instead of `if`s

pipeline/backend/docker/convert_test.go

@@ -86,9 +86,7 @@ func TestSplitVolumeParts(t *testing.T) {
 	for _, test := range testdata {
 		results, err := splitVolumeParts(test.from)
 		if test.success != (err == nil) {
-			if reflect.DeepEqual(results, test.to) != test.success {
-				t.Errorf("Expect %q matches %q is %v", test.from, results, test.to)
-			}
+			assert.Equal(t, test.success, reflect.DeepEqual(results, test.to))
 		}
 	}
 }