govis: switch to testify tests

testify makes most bog-standard test checks much easier to read and
maintain, and is quite widely used. It wasn't really well known back
when govis was first written, but the migration is fairly
straight-forward for most tests.

Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>

pkg/govis/govis.go

@@ -17,6 +17,11 @@
 
 package govis
 
+import (
+	"strconv"
+	"strings"
+)
+
 // VisFlag manipulates how the characters are encoded/decoded
 type VisFlag uint
 
@@ -37,3 +42,40 @@ const (
 
 	VisWhite VisFlag = (VisSpace | VisTab | VisNewline)
 )
+
+// String pretty-prints VisFlag.
+func (vflags VisFlag) String() string {
+	flagNames := []struct {
+		name string
+		bits VisFlag
+	}{
+		{"VisOctal", VisOctal},
+		{"VisCStyle", VisCStyle},
+		{"VisSpace", VisSpace},
+		{"VisTab", VisTab},
+		{"VisNewline", VisNewline},
+		{"VisSafe", VisSafe},
+		{"VisNoSlash", VisNoSlash},
+		{"VisHTTPStyle", VisHTTPStyle},
+		{"VisGlob", VisGlob},
+	}
+	var (
+		flagSet  = make([]string, 0, len(flagNames))
+		seenBits VisFlag
+	)
+	for _, flag := range flagNames {
+		if vflags&flag.bits == flag.bits {
+			seenBits |= flag.bits
+			flagSet = append(flagSet, flag.name)
+		}
+	}
+	// If there were any remaining flags specified we don't know the name of,
+	// just add them in an 0x... format.
+	if remaining := vflags &^ seenBits; remaining != 0 {
+		flagSet = append(flagSet, "0x"+strconv.FormatUint(uint64(remaining), 16))
+	}
+	if len(flagSet) == 0 {
+		return "0"
+	}
+	return strings.Join(flagSet, "|")
+}