internal/rosa/gnu: test skip helper

The terribleness of GNU invites interesting helpers.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/rosa/gnu.go

@@ -2,10 +2,47 @@ package rosa
 
 import (
 	"runtime"
+	"slices"
+	"strconv"
+	"strings"
 
 	"hakurei.app/internal/pkg"
 )
 
+// skipGNUTests generates a string for skipping specific tests by number in a
+// GNU test suite. This is nontrivial because the test suite does not support
+// excluding tests in any way, so ranges for all but the skipped tests have to
+// be specified instead.
+//
+// For example, to skip test 764, ranges around the skipped test must be
+// specified:
+//
+//	1-763 765-
+//
+// Tests are numbered starting from 1. The resulting string is unquoted.
+func skipGNUTests(tests ...int) string {
+	tests = slices.Clone(tests)
+	slices.Sort(tests)
+
+	var buf strings.Builder
+
+	if tests[0] != 1 {
+		buf.WriteString("1-")
+	}
+
+	for i, n := range tests {
+		if n != 1 && (i == 0 || tests[i-1] != n-1) {
+			buf.WriteString(strconv.Itoa(n - 1))
+			buf.WriteString(" ")
+		}
+		if i == len(tests)-1 || tests[i+1] != n+1 {
+			buf.WriteString(strconv.Itoa(n + 1))
+			buf.WriteString("-")
+		}
+	}
+	return buf.String()
+}
+
 func (t Toolchain) newM4() (pkg.Artifact, string) {
 	const (
 		version  = "1.4.21"