diff --git a/remote/test/browser/page/browser_navigate.js b/remote/test/browser/page/browser_navigate.js
index d0fc796f2c87..d377f353d5b4 100644
--- a/remote/test/browser/page/browser_navigate.js
+++ b/remote/test/browser/page/browser_navigate.js
@@ -27,7 +27,6 @@ add_task(async function testBasicNavigation({ client }) {
 
   await loadEventFired;
   const currentFrame = await getTopFrame(client);
-  is(4, "4", "identical");
   is(frameId, currentFrame.id, "Page.navigate returns expected frameId");
 
   is(
diff --git a/remote/test/browser/runtime/browser_callFunctionOn.js b/remote/test/browser/runtime/browser_callFunctionOn.js
index 6afc91717c26..797763196181 100644
--- a/remote/test/browser/runtime/browser_callFunctionOn.js
+++ b/remote/test/browser/runtime/browser_callFunctionOn.js
@@ -118,7 +118,7 @@ add_task(async function awaitPromiseResolve({ client }) {
   });
 
   is(result.type, "number", "The type is correct");
-  is(result.subtype, null, "The subtype is null for numbers");
+  is(result.subtype, undefined, "The subtype is undefined for numbers");
   is(result.value, 42, "The result is the promise's resolution");
 });
 
@@ -133,7 +133,7 @@ add_task(async function awaitPromiseDelayedResolve({ client }) {
     executionContextId,
   });
   is(result.type, "number", "The type is correct");
-  is(result.subtype, null, "The subtype is null for numbers");
+  is(result.subtype, undefined, "The subtype is undefined for numbers");
   is(result.value, 42, "The result is the promise's resolution");
 });
 
@@ -318,7 +318,7 @@ add_task(async function objectId({ client }) {
   });
 
   is(result.type, "object", "The type is correct");
-  is(result.subtype, null, "The subtype is null for objects");
+  is(result.subtype, undefined, "The subtype is undefined for objects");
   ok(!!result.objectId, "Got an object id");
 
   // Then apply a method on this object
@@ -329,7 +329,7 @@ add_task(async function objectId({ client }) {
   });
 
   is(result2.type, "number", "The type is correct");
-  is(result2.subtype, null, "The subtype is null for numbers");
+  is(result2.subtype, undefined, "The subtype is undefined for numbers");
   is(result2.value, 42, "Expected value returned");
 });
 
@@ -345,7 +345,7 @@ add_task(async function objectIdArgumentReference({ client }) {
   });
 
   is(result.type, "object", "The type is correct");
-  is(result.subtype, null, "The subtype is null for objects");
+  is(result.subtype, undefined, "The subtype is undefined for objects");
   ok(!!result.objectId, "Got an object id");
 
   // Then increment the `foo` attribute of this JS object,
@@ -374,7 +374,7 @@ add_task(async function objectIdArgumentReference({ client }) {
   });
 
   is(result3.type, "object", "The type is correct");
-  is(result3.subtype, null, "The subtype is null for objects");
+  is(result3.subtype, undefined, "The subtype is undefined for objects");
   // Remote objects don't have unique ids. So you may have multiple object ids
   // that reference the same remote object
   ok(!!result3.objectId, "Got an object id");
diff --git a/remote/test/browser/runtime/browser_callFunctionOn_returnByValue.js b/remote/test/browser/runtime/browser_callFunctionOn_returnByValue.js
index eaf995ae8530..364759911652 100644
--- a/remote/test/browser/runtime/browser_callFunctionOn_returnByValue.js
+++ b/remote/test/browser/runtime/browser_callFunctionOn_returnByValue.js
@@ -9,8 +9,8 @@ add_task(async function returnAsObjectTypes({ client }) {
   const { id: executionContextId } = await enableRuntime(client);
 
   const expressions = [
-    { expression: "({foo:true})", type: "object", subtype: null },
-    { expression: "Symbol('foo')", type: "symbol", subtype: null },
+    { expression: "({foo:true})", type: "object", subtype: undefined },
+    { expression: "Symbol('foo')", type: "symbol", subtype: undefined },
     { expression: "new Promise(()=>{})", type: "object", subtype: "promise" },
     { expression: "new Int8Array(8)", type: "object", subtype: "typedarray" },
     { expression: "new WeakMap()", type: "object", subtype: "weakmap" },
diff --git a/remote/test/browser/runtime/browser_evaluate.js b/remote/test/browser/runtime/browser_evaluate.js
index 1bb47a998ecd..61ab7b9dbe4a 100644
--- a/remote/test/browser/runtime/browser_evaluate.js
+++ b/remote/test/browser/runtime/browser_evaluate.js
@@ -35,7 +35,7 @@ add_task(async function awaitPromiseResolve({ client }) {
   });
 
   is(result.type, "number", "The type is correct");
-  is(result.subtype, null, "The subtype is null for numbers");
+  is(result.subtype, undefined, "The subtype is undefined for numbers");
   is(result.value, 42, "The result is the promise's resolution");
 });
 
@@ -66,7 +66,7 @@ add_task(async function awaitPromiseDelayedResolve({ client }) {
     awaitPromise: true,
   });
   is(result.type, "number", "The type is correct");
-  is(result.subtype, null, "The subtype is null for numbers");
+  is(result.subtype, undefined, "The subtype is undefined for numbers");
   is(result.value, 42, "The result is the promise's resolution");
 });
 
@@ -193,8 +193,8 @@ add_task(async function returnAsObjectTypes({ client }) {
   await enableRuntime(client);
 
   const expressions = [
-    { expression: "({foo:true})", type: "object", subtype: null },
-    { expression: "Symbol('foo')", type: "symbol", subtype: null },
+    { expression: "({foo:true})", type: "object", subtype: undefined },
+    { expression: "Symbol('foo')", type: "symbol", subtype: undefined },
     { expression: "new Promise(()=>{})", type: "object", subtype: "promise" },
     { expression: "new Int8Array(8)", type: "object", subtype: "typedarray" },
     { expression: "new WeakMap()", type: "object", subtype: "weakmap" },
diff --git a/remote/test/browser/runtime/browser_getProperties.js b/remote/test/browser/runtime/browser_getProperties.js
index 12f0cacd35f9..84229db10e59 100644
--- a/remote/test/browser/runtime/browser_getProperties.js
+++ b/remote/test/browser/runtime/browser_getProperties.js
@@ -34,7 +34,7 @@ async function testGetOwnSimpleProperties({ Runtime }, contextId) {
     contextId,
     expression: "({ bool: true, fun() {}, int: 1, object: {}, string: 'foo' })",
   });
-  is(result.subtype, null, "JS Object have no subtype");
+  is(result.subtype, undefined, "JS Object has no subtype");
   is(result.type, "object", "The type is correct");
   ok(!!result.objectId, "Got an object id");
 
@@ -94,7 +94,7 @@ async function testGetPrototypeProperties({ Runtime }, contextId) {
     contextId,
     expression: "({ foo: 42 })",
   });
-  is(result.subtype, null, "JS Object have no subtype");
+  is(result.subtype, undefined, "JS Object has no subtype");
   is(result.type, "object", "The type is correct");
   ok(!!result.objectId, "Got an object id");
 
@@ -121,7 +121,7 @@ async function testGetGetterSetterProperties({ Runtime }, contextId) {
     expression:
       "({ get prop() { return this.x; }, set prop(v) { this.x = v; } })",
   });
-  is(result.subtype, null, "JS Object have no subtype");
+  is(result.subtype, undefined, "JS Object has no subtype");
   is(result.type, "object", "The type is correct");
   ok(!!result.objectId, "Got an object id");
 
@@ -156,7 +156,7 @@ async function testGetGetterSetterProperties({ Runtime }, contextId) {
     ],
   });
   is(result3.type, "number", "The type is correct");
-  is(result3.subtype, null, "The subtype is null for numbers");
+  is(result3.subtype, undefined, "The subtype is undefined for numbers");
   is(result3.value, 42, "The getter returned the value set by the setter");
 }
 
@@ -165,7 +165,7 @@ async function testGetCustomProperty({ Runtime }, contextId) {
     contextId,
     expression: `const obj = {}; Object.defineProperty(obj, "prop", { value: 42 }); obj`,
   });
-  is(result.subtype, null, "JS Object have no subtype");
+  is(result.subtype, undefined, "JS Object has no subtype");
   is(result.type, "object", "The type is correct");
   ok(!!result.objectId, "Got an object id");
 
diff --git a/remote/test/browser/runtime/browser_remoteObjects.js b/remote/test/browser/runtime/browser_remoteObjects.js
index cc4435e33d9c..07453ffa5983 100644
--- a/remote/test/browser/runtime/browser_remoteObjects.js
+++ b/remote/test/browser/runtime/browser_remoteObjects.js
@@ -31,7 +31,7 @@ async function testObjectRelease({ Runtime }, contextId) {
     contextId,
     expression: "({ foo: 42 })",
   });
-  is(result.subtype, null, "JS Object have no subtype");
+  is(result.subtype, undefined, "JS Object has no subtype");
   is(result.type, "object", "The type is correct");
   ok(!!result.objectId, "Got an object id");