func nTC(input interface{}, v interface{}) testCase {
	tc := testCase{input: input}
	tc.expected = v
	return tc
}
nTC => newTestCase. It's meant to save some typing.
package munge
import (
	"fmt"
	"regexp"
	"github.com/stretchr/testify/suite"
)
type testCase struct {
	input    interface{}
	expected interface{}
	errRegex *regexp.Regexp
}