refactor: rename testbench to test.

- rename testbench to test.
- add benchmark for future development.

test/yycc/num/op.cpp

@@ -0,0 +1,19 @@
+#include <gtest/gtest.h>
+#include <yycc.hpp>
+#include <yycc/num/op.hpp>
+
+#include <yycc/rust/prelude.hpp>
+
+#define OP ::yycc::num::op
+
+namespace yycctest::num::op {
+
+    TEST(NumOp, DivCeil) {
+        // Normal case
+        EXPECT_EQ(OP::div_ceil<u32>(8, 4), UINT32_C(2));
+        EXPECT_EQ(OP::div_ceil<u32>(7, 4), UINT32_C(2));
+        // Limit case
+        EXPECT_EQ(OP::div_ceil<u8>(255, 2), UINT8_C(128));
+    }
+
+}