diff --git a/integration/proto2/proto2-optionals-test.ts b/integration/proto2/proto2-optionals-test.ts
index bdea35217..db578ba65 100644
--- a/integration/proto2/proto2-optionals-test.ts
+++ b/integration/proto2/proto2-optionals-test.ts
@@ -1,4 +1,4 @@
-import { OptionalsTest } from "./simple";
+import { OptionalsTest, OptionalsTest_TranslationsEntry } from "./simple";
 
 describe("proto2-optionals", () => {
   it("it compiles", () => {
@@ -13,4 +13,21 @@ describe("proto2-optionals", () => {
 
     expect(decoded).toEqual(message);
   });
+
+  it("throws an error if fromJSON is called without providing all required fields", () => {
+    expect(() => {
+      OptionalsTest.fromJSON({});
+    }).toThrow("Required field OptionalsTest.reqId is not set");
+  });
+
+  it("does not throw an error when using fromPartial and assigns the correct default value", () => {
+    const message = OptionalsTest.fromPartial({});
+    expect(message.reqId).toBe(0);
+    expect(message.reqDefvalId).toBe(100);
+  });
+
+  it("assigns key-value pairs a defined default value even though technically they are optional", () => {
+    const message = OptionalsTest_TranslationsEntry.create();
+    expect(message).toEqual({ key: "", value: "" });
+  });
 });