diff --git a/libs/proxy/json/src/value.rs b/libs/proxy/json/src/value.rs
index 705af9603e..d8dc6068fc 100644
--- a/libs/proxy/json/src/value.rs
+++ b/libs/proxy/json/src/value.rs
@@ -32,6 +32,13 @@ impl ValueEncoder for &str {
     }
 }
 
+impl ValueEncoder for String {
+    #[inline]
+    fn encode(self, v: ValueSer<'_>) {
+        self.as_str().encode(v);
+    }
+}
+
 impl ValueEncoder for fmt::Arguments<'_> {
     #[inline]
     fn encode(self, v: ValueSer<'_>) {
@@ -102,6 +109,13 @@ impl KeyEncoder for &str {
     }
 }
 
+impl KeyEncoder for String {
+    #[inline]
+    fn write_key<'a>(self, obj: &'a mut ObjectSer) -> ValueSer<'a> {
+        self.as_str().write_key(obj)
+    }
+}
+
 impl KeyEncoder for fmt::Arguments<'_> {
     #[inline]
     fn write_key<'a>(self, obj: &'a mut ObjectSer) -> ValueSer<'a> {
diff --git a/libs/proxy/json/tests/test.rs b/libs/proxy/json/tests/test.rs
new file mode 100644
index 0000000000..b738591ef2
--- /dev/null
+++ b/libs/proxy/json/tests/test.rs
@@ -0,0 +1,180 @@
+use json::Null;
+use json::ValueEncoder;
+use std::collections::BTreeMap;
+
+macro_rules! treemap {
+    () => {
+        BTreeMap::new()
+    };
+    ($($k:expr => $v:expr),+ $(,)?) => {
+        {
+            let mut m = BTreeMap::new();
+            $(
+                m.insert($k, $v);
+            )+
+            m
+        }
+    };
+}
+
+fn test_encode_ok<'a, T>(errors: impl IntoIterator<Item = (T, &'a str)>)
+where
+    T: ValueEncoder,
+{
+    for (value, out) in errors {
+        let s = json::value_to_string!(|v| value.encode(v));
+        assert_eq!(&*s, out);
+    }
+}
+
+#[test]
+fn test_write_null() {
+    let tests = [(Null, "null")];
+    test_encode_ok(tests);
+}
+
+#[test]
+fn test_write_u64() {
+    let tests = [(3u64, "3"), (u64::MAX, &u64::MAX.to_string())];
+    test_encode_ok(tests);
+}
+
+#[test]
+fn test_write_i64() {
+    let tests = [
+        (3i64, "3"),
+        (-2i64, "-2"),
+        (-1234i64, "-1234"),
+        (i64::MIN, &i64::MIN.to_string()),
+    ];
+    test_encode_ok(tests);
+}
+
+#[test]
+fn test_write_f64() {
+    let tests = [
+        (3.0, "3.0"),
+        (3.1, "3.1"),
+        (-1.5, "-1.5"),
+        (0.5, "0.5"),
+        (f64::MIN, "-1.7976931348623157e308"),
+        (f64::MAX, "1.7976931348623157e308"),
+        (f64::EPSILON, "2.220446049250313e-16"),
+    ];
+    test_encode_ok(tests);
+}
+
+#[test]
+fn test_write_str() {
+    let tests = [
+        // normal
+        ("", "\"\""),
+        ("foo", "\"foo\""),
+        // ascii escape chars.
+        ("\"", "\"\\\"\""),
+        ("\x08", "\"\\b\""),
+        ("\n", "\"\\n\""),
+        ("\r", "\"\\r\""),
+        ("\t", "\"\\t\""),
+        ("\x07", "\"\\u0007\""),
+        // unicode not escaped.
+        ("\u{12ab}", "\"\u{12ab}\""),
+        ("\u{AB12}", "\"\u{AB12}\""),
+        ("\u{1F395}", "\"\u{1F395}\""),
+    ];
+    test_encode_ok(tests);
+}
+
+#[test]
+fn test_write_bool() {
+    let tests = [(true, "true"), (false, "false")];
+    test_encode_ok(tests);
+}
+
+#[test]
+fn test_write_list() {
+    test_encode_ok([
+        (vec![], "[]"),
+        (vec![true], "[true]"),
+        (vec![true, false], "[true,false]"),
+    ]);
+
+    test_encode_ok([
+        (vec![vec![], vec![], vec![]], "[[],[],[]]"),
+        (vec![vec![1, 2, 3], vec![], vec![]], "[[1,2,3],[],[]]"),
+        (vec![vec![], vec![1, 2, 3], vec![]], "[[],[1,2,3],[]]"),
+        (vec![vec![], vec![], vec![1, 2, 3]], "[[],[],[1,2,3]]"),
+    ]);
+}
+
+#[test]
+fn test_write_object() {
+    test_encode_ok([
+        (treemap!(), "{}"),
+        (treemap!("a".to_owned() => true), "{\"a\":true}"),
+        (
+            treemap!(
+                "a".to_owned() => true,
+                "b".to_owned() => false,
+            ),
+            "{\"a\":true,\"b\":false}",
+        ),
+    ]);
+
+    test_encode_ok([
+        (
+            treemap![
+                "a".to_owned() => treemap![],
+                "b".to_owned() => treemap![],
+                "c".to_owned() => treemap![],
+            ],
+            "{\"a\":{},\"b\":{},\"c\":{}}",
+        ),
+        (
+            treemap![
+                "a".to_owned() => treemap![
+                    "a".to_owned() => treemap!["a" => vec![1,2,3]],
+                    "b".to_owned() => treemap![],
+                    "c".to_owned() => treemap![],
+                ],
+                "b".to_owned() => treemap![],
+                "c".to_owned() => treemap![],
+            ],
+            "{\"a\":{\"a\":{\"a\":[1,2,3]},\"b\":{},\"c\":{}},\"b\":{},\"c\":{}}",
+        ),
+        (
+            treemap![
+                "a".to_owned() => treemap![],
+                "b".to_owned() => treemap![
+                    "a".to_owned() => treemap!["a" => vec![1,2,3]],
+                    "b".to_owned() => treemap![],
+                    "c".to_owned() => treemap![],
+                ],
+                "c".to_owned() => treemap![],
+            ],
+            "{\"a\":{},\"b\":{\"a\":{\"a\":[1,2,3]},\"b\":{},\"c\":{}},\"c\":{}}",
+        ),
+        (
+            treemap![
+                "a".to_owned() => treemap![],
+                "b".to_owned() => treemap![],
+                "c".to_owned() => treemap![
+                    "a".to_owned() => treemap!["a" => vec![1,2,3]],
+                    "b".to_owned() => treemap![],
+                    "c".to_owned() => treemap![],
+                ],
+            ],
+            "{\"a\":{},\"b\":{},\"c\":{\"a\":{\"a\":[1,2,3]},\"b\":{},\"c\":{}}}",
+        ),
+    ]);
+}
+
+#[test]
+fn test_write_option() {
+    test_encode_ok([(None, "null"), (Some("jodhpurs"), "\"jodhpurs\"")]);
+
+    test_encode_ok([
+        (None, "null"),
+        (Some(vec!["foo", "bar"]), "[\"foo\",\"bar\"]"),
+    ]);
+}