lib/stringsutil: add tests for LimitStringLen() function

lib/stringsutil/stringsutil.go

@@ -5,12 +5,12 @@ package stringsutil
 // If len(s) > maxLen, then s is replaced with "s_prefix..s_suffix",
 // so the total length of the returned string doesn't exceed maxLen.
 func LimitStringLen(s string, maxLen int) string {
-	if len(s) <= maxLen || maxLen < 4 {
+	if maxLen < 4 {
+		maxLen = 4
+	}
+	if len(s) <= maxLen {
 		return s
 	}
 	n := (maxLen / 2) - 1
-	if n < 0 {
-		n = 0
-	}
 	return s[:n] + ".." + s[len(s)-n:]
 }

lib/stringsutil/stringsutil_test.go

@@ -0,0 +1,24 @@
+package stringsutil
+
+import (
+	"testing"
+)
+
+func TestLimitStringLen(t *testing.T) {
+	f := func(s string, maxLen int, resultExpected string) {
+		t.Helper()
+
+		result := LimitStringLen(s, maxLen)
+		if result != resultExpected {
+			t.Fatalf("unexpected result; got %q; want %q", result, resultExpected)
+		}
+	}
+
+	f("", 1, "")
+	f("a", 10, "a")
+	f("abc", 2, "abc")
+	f("abcd", 3, "abcd")
+	f("abcde", 3, "a..e")
+	f("abcde", 4, "a..e")
+	f("abcde", 5, "abcde")
+}