diff --git a/runner/src/index.ts b/runner/src/index.ts
index e9c56fc..5021a64 100644
--- a/runner/src/index.ts
+++ b/runner/src/index.ts
@@ -6,6 +6,11 @@ const EmbeddedObject = {
   anEnumArray: ["option1", "option2", "option3"],
   anIntArray: [1, 2, 3],
   aDate: "2024-07-23T16:03:34.000Z",
+  aDateArray: [
+    "2024-07-23T16:03:34.000Z",
+    "2024-08-23T16:03:35.000Z",
+    "2024-09-23T16:03:36.000Z",
+  ]
 };
 
 const inputBufferString = "Hello 🌍 World!🌍";
@@ -81,6 +86,30 @@ export function test() {
     }
   });
 
+  Test.group("schema v1-draft mutating object", () => {
+    let input = JSON.stringify(EmbeddedObject);
+    let output: typeof EmbeddedObject = Test.call("mutateObject", input).json();
+    Test.assertEqual('has bools', output.aBoolArray.length, 3)
+    output.aBoolArray.forEach((b, i) => {
+      Test.assertEqual(`inverted ${b}`, b, !EmbeddedObject.aBoolArray[i])
+    })
+
+    Test.assertEqual('has strings', output.aStringArray.length, 3)
+    output.aStringArray.forEach((b, i) => {
+      Test.assertEqual(`mutated ${b}`, b, `hello ${EmbeddedObject.aStringArray[i]}`)
+    })
+
+    Test.assertEqual('has ints', output.anIntArray.length, 3)
+    output.anIntArray.forEach((b, i) => {
+      Test.assertEqual(`mutated ${b}`, b, EmbeddedObject.anIntArray[i] + 1)
+    })
+
+    Test.assertEqual('has dates', output.aDateArray.length, 3)
+    output.aDateArray.forEach((b, i) => {
+      Test.assertEqual(`one second added ${b}`, b, new Date((new Date(EmbeddedObject.aDateArray[i]).getTime() + 1000)).toISOString())
+    })
+  });
+
   Test.group("check signature and type variations", () => {
     // should call a the `noInputWithOutputHost` host function passing it
     // a string "noInputWithOutputHost" which it should return
diff --git a/schema.yaml b/schema.yaml
index 1fd9f6f..3ca1e2e 100644
--- a/schema.yaml
+++ b/schema.yaml
@@ -275,6 +275,24 @@ exports:
         source: |
           input.aBuffer = input.aBuffer.replace(b"Hello", b"Goodbye"); return input
 
+  mutateObject:
+    description: |
+      This function takes an EmbeddedObject and mutates it. It tests that
+      types are properly cast to their language equivalents
+    codeSamples:
+      - lang: typescript
+        source: |
+          input.aBoolArray = input.aBoolArray.map(v => !v)
+          input.aStringArray = input.aStringArray.map(v => `hello ${v}`)
+          input.anIntArray = input.anIntArray.map(v => v + 1)
+          input.aDateArray = input.aDateArray.map(v => new Date(v.getTime() + 1000)) // add one second
+          return input
+    input:
+      contentType: application/json
+      $ref: "#/components/schemas/EmbeddedObject"
+    output:
+      contentType: application/json
+      $ref: "#/components/schemas/EmbeddedObject"
 imports:
   reflectJsonObjectHost:
     description: |
@@ -352,6 +370,12 @@ components:
           type: array
           items:
             type: integer
+        aDateArray:
+          description: a date array
+          type: array
+          items:
+            type: string
+            format: date-time
         aDate:
           description: a date
           type: string