Add tests for string search configuration

Introduces tests for smart search defaults and strategy selection in the string module, including cases for minimum pattern length and small patterns.

Author: lupodevelop

test/str_config_test.gleam

@@ -0,0 +1,25 @@
+import str
+import gleam/list
+// removed unused import
+
+pub fn smart_search_default_test() {
+  assert str.smart_search_enabled() == False
+}
+
+fn make_repeat(s: String, n: Int) -> String {
+  list.fold(list.range(1, n), "", fn(acc, _) { acc <> s })
+}
+
+pub fn choose_strategy_min_pattern_test() {
+  let min = str.kmp_min_pattern_len()
+  // pattern of length `min` should prefer KMP
+  let pat = make_repeat("a", min)
+  let strategy = str.choose_search_strategy("some text", pat)
+  assert strategy == str.Kmp
+}
+
+pub fn choose_strategy_small_pattern_test() {
+  let pat = "a"
+  let strategy = str.choose_search_strategy("short", pat)
+  assert strategy == str.Sliding
+}