feat: add Rust env namespace

testbench/CMakeLists.txt

@@ -12,6 +12,7 @@ PRIVATE
     yycc/constraint/builder.cpp
     yycc/patch/ptr_pad.cpp
     yycc/patch/fopen.cpp
+    yycc/rust/env.cpp
     yycc/string/op.cpp
     yycc/string/reinterpret.cpp
     yycc/num/parse.cpp

testbench/yycc/rust/env.cpp

@@ -0,0 +1,45 @@
+#include <gtest/gtest.h>
+#include <yycc.hpp>
+#include <yycc/rust/env.hpp>
+
+#define ENV ::yycc::rust::env
+
+namespace yycctest::rust::env {
+
+    constexpr char8_t VAR_NAME[] = u8"HOMER";
+    constexpr char8_t VAR_VALUE[] = u8"doh";
+
+    TEST(RustEnv, All) {
+        // Write a new variable should okey
+        {
+            auto rv = ENV::set_var(VAR_NAME, VAR_VALUE);
+            ASSERT_TRUE(rv.has_value());
+        }
+
+        // After writing, we can fetch it and check its value.
+        {
+            auto rv = ENV::get_var(VAR_NAME);
+            ASSERT_TRUE(rv.has_value());
+            EXPECT_EQ(rv.value(), VAR_VALUE);
+        }
+
+        // The we can delete it.
+        {
+            auto rv = ENV::del_var(VAR_NAME);
+            ASSERT_TRUE(rv.has_value());
+        }
+
+        // Delete inexisting variable also should be okey
+        {
+            auto rv = ENV::del_var(VAR_NAME);
+            ASSERT_TRUE(rv.has_value());
+        }
+
+        // After deleting, we can not fetch it anymore.
+        {
+            auto rv = ENV::get_var(VAR_NAME);
+            ASSERT_FALSE(rv.has_value());
+        }
+    }
+
+}